Ten d o n I n j u r i e s o f t h e H i p

Catherine N. Petchprapa, MD*, Jenny T. Bencardino, MD

KEYWORDS
 MR imaging  Hip  Tendon pathology  Overuse injury

KEY POINTS
 History and clinical examination may not reliably stratify those patients with arthritic pain from those
with nonarthritic pain.
 MR imaging is an important adjunct to the clinical examination because of its ability to evaluate the
joint as well as the periarticular structures, which can be a source of symptoms.
 An anatomy-based search process can facilitate MR imaging interpretation and ensure that both
common and less common entities are considered in the differential diagnosis.

INTRODUCTION Hip pain can be characterized as anterior,

lateral, or posterior. The content of this review is
One in 164 visits to family physicians1 is for hip pain. organized using this anatomic approach (Fig. 1):
Unfortunately, hip pain can be a vexing clinical
problem; symptoms may be protean, referred, and  Anterior pain (excluding osteoarthritis):
poorly localized. Moreover, history and physical enthesial and proximal iliotibial band
examination have been found unreliable in discrim- (ITB) pathology, disorders of the iliopsoas
inating between the intra-articular or extra-articular tendon (internal snapping hip and iliopsoas
sources of hip pain. In approximately half of the impingement), and disorders of rectus
patients studied, Martin and colleagues2 deter- femoris
mined that extra-articular pathology was respon-  Lateral pain: disorders of the hip abductor
sible for patient symptoms despite imaging tendons and external snapping hip syn-
evidence for labral abnormalities. drome (ESHS)
Overuse injuries, including tendinopathies, are  Posterior pain: disorders of the hamstring
on the rise.3 The higher level of performance of tendons
competitive and recreational athletes, an emphasis
on the health benefits of physical activity leading to Disorders of the ischiofemoral space and groin
greater sports participation in all age groups, and pain are discussed elsewhere in this issue by Tor-
increased longevity of the population probably all riani and colleagues, and Zoga and colleagues,
contribute to this trend. respectively.
These points stress the importance of consid-
ering tendon pathology in the differential diagnosis
MR IMAGING TECHNIQUE
and the need for imaging in the work-up in patients
with hip pain. MR imaging augments clinical eval- According to the American College of Radiology,
uation by providing information about the hip joint plain radiographs of the pelvis and hip are the
as well as the periarticular structures, which can most appropriate imaging study for the initial eval-
be a source of symptoms. uation of chronic hip pain. Radiographs may reveal
Imaging evaluation for extra-articular causes of fractures, osteoarthritis, hydroxyapatite crystal
hip pain necessitates knowledge of normal deposition diseases, and other common entities
anatomy and common pathologic tendon condi- that may explain symptomatology. Initial radio-
tions in this region. graphic findings and clinical information can then
mri.theclinics.com

Department of Radiology, NYU Langone Medical Center, Hospital for Joint Diseases, 301 East 17th Street,
New York, NY 10003, USA
* Corresponding author.
E-mail address: petchc01@nyumc.org

Magn Reson Imaging Clin N Am 21 (2013) 75–96

http://dx.doi.org/10.1016/j.mric.2012.09.004
1064-9689/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved.
76 Petchprapa & Bencardino

Fig. 1. Overview of tendon pathology around the hip.

guide the choice of more advanced imaging. In relevant to management), axial fat-suppressed
cases of suspected musculotendinous etiology, T2, axial oblique PD, sagittal fat-suppressed PD,
noncontrast MR imaging is the next most and coronal PD are performed using a high-
commonly performed study because of its ability resolution technique that uses a flexible surface
to diagnose the myriad potential osseous and coil wrapped around the affected hip (Table 1).
soft tissue causes of hip pain around the pelvis.4 The affected hip is positioned closest to isocenter
Tendon pathology can be evaluated on stan- with the surface coil in place at the start of the
dard MR imaging planes. MR imaging protocols examination; off-isocenter position optimizes
can be standardized; the authors use 3 imaging imaging of the affected hip and in the authors’
protocols. All start with large field of view (FOV) practice does not have a significant impact on
coronal short tau inversion recovery (STIR) images the diagnostic quality of the large FOV sequence
of the pelvis using the body coil; this provides an for the remainder of the pelvis (Fig. 2).
overview of the pelvis and allows a radiologist/ For patients over age 50 (in whom marrow
technologist to modify the imaging protocol to abnormalities, including fractures and metastatic
evaluate unexpected pathology if necessary. disease, may be a concern), the large FOV STIR
The protocol for the bony pelvis continues with coronal sequence is followed by a large FOV T1
large FOV imaging of the pelvis using anatomic coronal sequence (Table 2). Subsequent coronal,
(T1 and proton density [PD]) and fluid-sensitive sagittal, and axial images are done of the affected
(fat-suppressed T2 or PD) sequences, and a sagittal hip only.
sequence through the affected side if there is Skin markers placed in the region of symptoms
symptom laterality. can help ensure adequate imaging coverage and
In patients younger than 50 years of age (in direct attention to the region of clinical concern
whom diagnosing intra-articular pathology is during image interpretation.

Table 1
Protocol for routine hip, patients under 50 years old

Sequence Plane Slice Thickness Tr Te FOV Matrix Comment

STIR Cor 5 mm 4000 35 350 192  256 Cover whole pelvis
PD TSE Cor 3 mm 3000–3500 34–38 160 192  256 Unilateral
PD TSE FS Sag 3 mm 2900–3000 22–35 160 256  256 Unilateral
T2 TSE FS Ax Straight 3 mm 3500–4500 40 200 224  256 Unilateral
PD TSE Obl Ax 3 mm 2800–3000 33 140–160 224  256 Unilateral

Abbreviations: STIR, short tau inversion recovery; PD, proton density; TSE, turbo spin echo; FS, fat suppressed; Cor,
coronal; Sag, sagittal; Ax, axial; Obl, oblique; Tr, repetition time; Te, excitation time; FOV, field of view.
 Tendon Injuries of the Hip 77

may heal over time and leave the tendon thick-

ened, thinned, irregular, or lax. Full-thickness tears
are defined as complete fiber discontinuity and
can be associated with tendon retraction, fluid
gap, and muscle atrophy (Fig. 5).
Spuriously increased intratendinous signal may
be the result of magic angle phenomenon. Seen
on sequences with short echo times, the signal in
a tendon may increase as the orientation of the in-
tratendinous collagen is aligned at an angle with the
main magnetic field. This is greatest at 55% and
Fig. 2. Patient positioning. The flexible coil is placed can be mitigated with the use of longer echo times
over the affected hip and patient positioned with (30 ms for gradient echo, 40 ms for spin echo, and
the affected hip closest to isocenter. 70 ms for fast spin-echo imaging at 1.5 T).6
Decreased tendon signal can be related to the
GENERAL CONSIDERATIONS/PITFALLS/ deposition of basic calcium phosphate, such as
CAVEATS hydroxyapatite, in the setting of calcific tendinitis.
This can be clinically silent; symptomatic crystal
Tendons are designed to transmit forces gener- deposition is most common in patients in their
ated from muscle contraction to bone. Their 40s to 60s.7 The hip is the second most commonly
tensile strength is owed in large part to densely affected joint; calcium deposits are most common
packed and aligned collagen fibers. Thus, healthy around the greater trochanter (hip abductor
tendons do not rupture under normal conditions. tendons) and ischial tuberosity (hamstring
Repetitive submaximal tendon loading due to tendons). They are also seen at the femoral inser-
chronic overuse, however, results in tendon tion of the gluteus maximus tendon and at the
degeneration; this reduces the tendon’s strength origin of rectus femoris and vastus musculature
and puts it at risk for failure. (Fig. 6). Initial patient presentation can be
Tendons undergo stereotypic changes with dramatic. The painful inflammatory response can
aging and injury regardless of their location. This manifest as bone and soft tissue edema8 and
alters their size, signal, and morphology on bone erosions, which can mimic infection or malig-
imaging. Peritendinitis represents the earliest nancy9,10 both clinically and on MR imaging.
injury, and manifests as increased T2 signal Although osseous involvement is rare, when
around the tendon (Fig. 3).5 Tendinosis or tendin- present in the hip, the proximal linea aspera of
opathy is the result of mechanical, degenerative, the femur is most likely affected (see Fig. 6A, B).
or overuse injuries. Whether the result of myxoid, Enthesial calcifications without a discrete soft
hypoxic, hyaline, fatty, fibrinoid, or calcific degen- tissue mass are substantiating evidence for this
eration, structural changes and accumulated diagnosis on MR imaging.11 Plain radiographs
degradation byproducts leave the tendon more and CT may help to confirm soft tissue calcifica-
prone to injury. This is reflected on MR imaging tions when they are not evident on MR imaging
as an increase in size and signal heterogeneity (see Fig. 6).
(see Fig. 3). Tears within a weakened tendon are “Treat the patient, not the imaging” could not be
identified as fluid-filled defects on PD, T2, or truer than in musculoskeletal imaging. Imaging-
STIR sequences (Fig. 4B). Partial thickness tears detected pathologic changes in the hip abductor

Table 2
Protocol for routine hip, patients over 50 years old

Sequence Plane Slice Thickness Tr Te FOV Matrix Comment

STIR Cor 5 mm 4000 35 350 192  256 Cover whole pelvis
T1 SE Cor 5 mm 500–735 12 350 240  320 Cover whole pelvis
PD TSE Cor 3 mm 3000–3500 34–38 160 192  256 Unilateral
PD TSE FS Sag 3 mm 2900–3000 22–35 160 256  256 Unilateral
T2 TSE FS Ax Straight 3 mm 3500–4500 40 200 224  256 Unilateral

Abbreviations: STIR, short tau inversion recovery; PD, proton density; TSE, turbo spin echo; FS, fat suppressed; Cor,
coronal; Sag, sagittal; Ax, axial; Obl, oblique; Tr, repetition time; Te, excitation time; FOV, field of view.
78 Petchprapa & Bencardino

Fig. 3. (A) Coronal PD and (B) axial oblique fat-suppressed PD-weighted images show increased tendon size and
signal related to tendinopathy ([A,B] solid arrows) and fluid signal around the tendon ([B] open arrow) related to
peritendinitis of the lateral portion of gluteus medius.

tendons12 and proximal hamstring tendons13 are  Disorders of the tendon origin of rectus
common in the asymptomatic population12 and femoris
underscore the point that not all tendinopathy is
symptomatic.3 Imaging findings do not always
correlate with clinical symptoms and it is the Abnormalities of the Origin of the Iliotibial
onus of the clinician to determine their relevance. Band
As the attachment site of tensor fascia lata as well
ANTERIOR PAIN as the external and internal abdominal oblique,
transverse abdominis, and gluteus medius,14 the
 Disorders of the origin of the ITB iliac crest apophysis is at risk for injury in adoles-
 Disorders of the iliopsoas tendon cent athletes. Seen in long distance runners
 Tendinopathy/tendon tears between the ages of 13 and 25 years, iliac crest
 Internal snapping hip apophysitis is the result of repetitive submaximal
 Iliopsoas impingement traction of the unfused apophysis.

Fig. 4. (A) Axial oblique and (B) sagittal fat-suppressed PD-weighted image in a 51-year-old runner complaining
of pain with prolonged sitting and sciatica. Severe tendinopathy ([A,B] open arrows) with superimposed partial
tear ([B] white bracket) of the semimembranosus tendon at its insertion. There is also fluid tracking around the
sciatic nerve (solid white arrow).
 Tendon Injuries of the Hip 79

Fig. 5. (A) Axial oblique and (B) sagittal fat-suppressed intermediate-weighted images and (C) coronal
PD-weighted image of the left hip. Complete gluteus minimus (white arrows) and lateral portion of gluteus med-
ius (open white arrows) tear. Both muscles are atrophied ([C] asterisk); therefore, surgical repair is not an option.
The posterior insertion of gluteus medius (dotted open white arrows) is intact.

Pathology at origin of the ITB has also been from gluteus maximus fascia before it continues
recently reported in a small cohort of adult distally toward its major insertion on the anterolat-
women15 from two disparate groups—young eral tibia at Gerdy tubercle.16
athletes and older overweight women. The ITB helps stabilize the extended knee and
hip,17 in part through the contraction of gluteus
Anatomy maximus and tensor fascia lata muscles, which
The ITB represents a thickening of the fascial tighten it.16
investiture of tensor fascia lata and gluteus maxi-
mus muscles. It originates at the iliac crest apoph- Imaging
ysis, which appears at approximately age 13 and Adequate coverage is the most important aspect
fuses at age 25. The ITB divides into deep and of imaging. The authors’ routine large FOV coronal
superficial layers to envelop the tensor fascia lata STIR sequence of the pelvis always includes the
muscle. At the hip, the ITB receives contributions iliac crest and allows evaluating this region on all
80 Petchprapa & Bencardino

Fig. 6. Calcific tendinitis. (A) Axial and (B) sagittal fat-suppressed PD-weighted images of the proximal right thigh
in 47-year-old man presenting with atraumatic hip and thigh pain. There is exuberant soft tissue edema centered
on an ovoid focus of low signal at the femoral insertion of the gluteus maximus tendon (open white arrow). The
subjacent cortex is thinned and irregular, and there is edema in the marrow space related to intraosseous exten-
sion. (C) Axial and (D) sagittal reformatted CT examination in another patient demonstrates a focal deposit with
internal fluid/calcium level (open white arrow) adjacent to the linea aspera of the femur.

patients. When pathology in this region is clinically Abnormalities Related to the Iliopsoas Tendon
suspected, this region is included in the axial and
The iliopsoas tendon represents the distal termina-
sagittal imaging FOV and both anatomic and
tion of the psoas major and iliacus muscles.
fluid-sensitive sequences are performed.
Together, these muscles flex the thigh, participate
In skeletally immature individuals, MR imaging
in lateral hip rotation, and contribute to pelvic
findings of apophyseal widening (3–5 mm), phys-
stability when seated.19 Abnormalities related to
eal signal hyperintensity, and marrow and muscle
the iliopsoas tendon include tendinopathy, tendon
edema on fluid-sensitive sequences18 have been
tears, internal snapping hip, and iliopsoas tendon
reported after injury (Fig. 7). Acute injury in adults
impingement.
manifests as edema in/around the ITB and within
its iliac enthesis on fluid-sensitive sequences
(Fig. 8). Thickening of the proximal ITB can be Anatomy
seen on both anatomic and fluid-sensitive The iliopsoas compartment is an elongated
sequences in the chronic setting. extraperitoneal space that extends from the
 Tendon Injuries of the Hip 81

Fig. 7. (A) Frontal radiograph of the pelvis of a 14-year-old runner on the track team who experienced a pop
while running. The iliac crest apophysis is avulsed and displaced on the right (open black arrow). (B) Coronal
and (C) axial fat-suppressed intermediate-weighted and (D) sagittal fat-suppressed PD-weighted images show
the avulsed cortical fragment ([C] open white arrow) with attached tensor fascia lata ([D] open arrow).

posterior mediastinum to the hip joint. It is roofed First, the tendons lie in a shallow groove in the
by the iliopsoas fascia and contains the psoas pelvic brim as they exit the pelvis. Second, they
major and iliacus muscles, and, when present, course immediately adjacent to the anterosuperior
the psoas minor muscle.20 aspect of the hip joint on the way to their insertion.
The long fusiform psoas major muscle arises Third, the iliacus and psoas tendons may merge
from lumbar and T12 transverse processes; the together or attach separately on the lesser
fan-like iliacus muscle arises from the inner iliac trochanter, the iliacus tendon more lateral than
fossa. As the 2 muscles merge at the L5-S2 level, the psoas, and the identification of 2 separate
a groove is formed at their lateral interface. It is tendons should not be mistaken for a tear.
through this fat-filled groove that the femoral nerve
and iliolumbar vessels bundle are transmitted.21 Iliopsoas tendinopathy/tendon tear
The composite iliopsoas muscle exits the pelvis Iliopsoas tendon pathology in adults is an uncom-
under the inguinal ligament; its tendon inserts on monly reported cause of anterior hip pain. Whereas
the lesser trochanter. In addition to its tendinous lesser trochanteric apophysitis and apophyseal
insertion, the iliacus muscle also inserts directly avulsions are common in active children and adoles-
on the anterior femur and distal lesser trochanter. cents, spontaneous lesser tuberosity avulsions in
When fluid distended, the iliopsoas bursa can be adults are considered pathologic until proved other-
seen between the iliacus muscle, the psoas wise (Fig. 9).23
tendon, and the anterior hip joint capsule.22 Iliopsoas tendinopathy and tendon rupture in
Three things are important about the iliopsoas adults are uncommon in radiology. Tendinopathy
musculotendinous unit with regards to pathology. may present as groin pain exacerbated by hip
82 Petchprapa & Bencardino

Fig. 8. (A) Coronal, (B) axial, and (C) sagittal fat-suppressed PD-weighted images of the pelvis in a 34-year-old
long distance runner who experienced sudden onset pain during marathon run 1 month previously. There is fluid
signal around the origin of the ITB at the iliac crest (white arrows).

flexion and adduction24 and has been reported in and audible snap. There are 3 categories of snap-
both kicking sports and in nonathletes.19 Sponta- ping hip: external (related to the iliotibial and or
neous rupture has been reported in elderly individ- gluteus maximus), intra-articular (related to intra-
uals who presented with severe groin pain after articular processes), and internal (related to the
minor trauma.25 Bui and colleagues24 retrospec- iliopsoas tendon).27
tively studied a small cohort of patients with
Anatomy At the pelvic brim, the iliopsoas tendon
ruptured iliopsoas tendons and found hip pain
the most common presenting symptom and lies in a shallow depression between the iliopecti-
occult fracture the most common clinical diag- neal eminence (medially) and the anterior inferior
nosis. Iliopsoas tendon and myotendinous injuries iliac spine (laterally); it is overlaid by the iliacus
had a prevalence of 0.66% in their series of 4862 and psoas muscles when the hip is flexed.28
pelvic and hip MR images; myotendinous strains The tendon undergoes normal medial transla-
tion as the hip goes from flexion to extension
and partial tears predominated among those
younger than 65 years old, and complete tears (Fig. 11). Gliding is facilitated by the iliopsoas
made up half of the injuries in those over age bursa, which lies between the iliopsoas muscle
65. Tendon tears are reported to occur close and the iliopectineal eminence.29
to or at the lesser trochanter insertion and com- In the setting of internal snapping hip syn-
monly spare the more lateral iliacus muscular drome, however, the tendon painfully catches
component.26 as the hip is brought from a flexed, abducted,
MR imaging features seen in tendon rupture and externally rotated position into extension
include a thickened and discontinuous tendon, with internal rotation. It may snap over the ilio-
a groin mass related to fluid around the torn and pectineal eminence, the femoral head,28,30 or
retracted psoas tendon and thickened distal iliop- over a lesser trochanteric exostosis31 as it does.
soas muscle, and proximal muscle swelling and The audible or palpable snapping can be volun-
edema (Fig. 10).24 tarily reproduced and occurs when stair climbing
or rising from a seated position.32 The tendon’s
proximity to the hip joint may cause one to
Internal snapping hip syndrome mistaken its symptoms for intra-articular
Snapping hip (coxa saltans) refers to a broad cate- pathology; furthermore, intra-articular pathology
gory of dynamic pathology that presents with pain and snapping hip may coexist.33
 Tendon Injuries of the Hip 83

Fig. 9. Frontal radiograph of the left hip (A) shows avulsion of the lesser trochanter (open black arrow) in this
63-year-old man with history of adenocarcinoma. (B) Axial T1 and (C) axial fat-suppressed T2-weighted images
show a destructive lesion in the lesser trochanter (open white arrow) and fluid and debris in the torn tendon
gap ([C]). (D) Prone axial oblique image of the patient obtained at time of CT-guided biopsy shows the lesion
in the lesser trochanter (open white arrow), histologically proved to be metastasis.

Asymptomatic hip snapping is present in up to (rest and corticosteroid injections) are the mainstay
10% of the population and can be differentiated of treatment. Endoscopic distal tendon release can
from snapping hip syndrome by the absence of pain. be considered in recalcitrant cases.32
Imaging There are no MR imaging–specific find-
ings for this entity. Sonography, however, can be Iliopsoas impingement
diagnostic. Not only can it document tendon dyski- Iliopsoas impingement in the setting of total hip
nesia and its relationship to the development of pain arthroplasty Tendon impingement in the setting
and symptoms but also it can be used to provide of total hip arthroplasty (THA) is well known to
guidance for anesthetic/steroid injections.34 Sono- orthopedic surgeons although it remains a poorly
graphic findings (inhomogeneous tendon appear- understood reason for postoperative pain. One
ance, hip effusion, and distended iliopsoas study reports 4.3% prevalence in patients with
bursa),35 however, are only inconsistently observed pain after THA.36
in patients with symptomatic snapping hip and have The iliopsoas tendon and the anterosuperior
not been corroborated by MR imaging. hip joint are closely apposed structures
Positive response to anesthetic challenge is (Fig. 12), and mechanical tendon impingement
considered diagnostic. Conservative measures may be caused by presence of a prominent or
84 Petchprapa & Bencardino

Fig. 10. (A) Axial and (B) sagittal fat-suppressed intermediate-weighted images in an 80-year-old woman who
presented with acute onset left hip pain and numbness. She was clinically suspected of having femoral nerve
entrapment. The iliopsoas tendon and muscle are completely torn and retracted ([B] open white arrow). There
is diffuse iliopspoas muscle edema on the left, along with fluid surrounding the femoral nerve in the pelvis
([A] solid white arrow).

malpositioned acetabular component,37,38 re- Iliopsoas impingement in the native hip Iliopsoas
tained cement,38 excessively long screws,38 an impingement in the native hip43 is a subject of
acetabular cage, or reinforcement ring.39 Limb debate at society meetings although not widely
length discrepancy is also another reported published in the literature.
cause of impingement.40 The arthroscopic observation of labral tears
Metal artifact–reducing MR imaging sequences immediately subjacent to the iliopsoas tendon
may increase the role of MR imaging in the future has led some investigators to postulate a new
with regards to the work-up of patients with pain pathomechanism for labral injury. In small series,
after arthroplasty.41 At present, imaging’s role is these labral tears were observed in patients who
in guiding diagnostic and therapeutic iliopsoas underwent arthroscopic iliopsoas tendon release
bursal injections (Fig. 13), which are a part of the for the treatment of internal snapping hip.44,45
diagnosis and conservative treatment of affected Heyworth and colleagues46 observed 7 of 24
individuals.42 patients with a tight psoas tendon overlying and

Fig. 11. Internal snapping hip. When the hip is flexed (A), the iliopsoas tendon (in grey) is lateral to the iliopectineal
eminence (blue star). When the hip is extended (B), the iliopsoas tendon translates medial to the iliopectineal eminence.
 Tendon Injuries of the Hip 85

Fig. 12. The relationship between the iliopsoas tendon and the hip joint. Drawing of the lateral view of the hip
(A) shows that the iliopsoas tendon (I) passes anterior to the anterior aspect of the hip and lies adjacent to the
anterosuperior labrum (open blue arrow). Long axis view of the femoral neck by ultrasound (B), axial oblique (C)
fat-suppressed PD and sagittal (D) fat-suppressed intermediate weighted images show the normally close rela-
tionship between the iliopsoas tendon ([B–D] open white arrow) with the anterior hip joint and the anterosupe-
rior labrum ([B–D] solid white arrow).

impinging on a torn or inflamed anterior labrum; in Blankenbaker and colleagues47 have begun to
these patients, labral impingement was relieved by investigate this entity with MR imaging in patients
psoas tendon release. The peculiar location of lab- intraoperatively diagnosed with and arthroscopi-
ral tears in this group (2–3 o’clock as opposed to cally treated with tenotomy at the labral level.
11:30–1 o’clock that is characteristic in femoroa-
cetabular impingement) led these investigators to
Disorders of the Proximal Rectus Femoris
postulate that labral injury was a result of mechan-
Tendon
ical compression of the capsulolabral complex by
the iliopsoas tendon. It remains to be seen if The long, fusiform muscle of rectus femoris origi-
a causal relationship exists, and if so, whether nates from 2 distinct tendons—the direct tendon
this can be prospectively diagnosed by imaging. from the anterior–inferior iliac spine and the
86 Petchprapa & Bencardino

Fig. 13. Contiguous axial CT images (A–C) from cranial to caudal after image-guided therapeutic injection of the
iliopsoas tendon sheath in a patient with clinically diagnosed iliopsoas impingement. Iodinated hyperdense
contrast outlines the iliopsoas tendon in its tendon sheath as it crosses anterior hip joint (open white arrows). Prox-
imity to the acetabular cup (asterisk) is best seen on the most caudal image (C). The patient reported symptomatic
relief after the injection.

indirect (also known as reflected) tendon from the are well known in adolescent athletes, particularly
superior acetabular ridge and hip joint capsule. soccer players in whom forceful kicking requires
The 2 tendons merge shortly after their origins to extreme hip hyperextension followed by forceful
form a conjoint tendon, with fibers from the direct hip flexion and knee extension.49 Injuries occur
composing much of the anterior tendon and fibers when a player’s kick is forcefully blocked or
from the indirect tendon composing much of the when kicking the air.50 Avulsion fractures in skele-
posterior.48 tally mature athletes are also reported; the avulsed
Rectus femoris extends the knee, flexes the hip, fragment is commonly small and can be difficult to
and stabilizes the pelvis on the femur in weight detect on plain radiographs.51 As they heal, the
bearing. It is the only component of the powerful abundant reactive ossification around these
quadriceps muscle group that crosses 2 joints injuries can be mistaken for ossified masses
and, as such, is the most commonly injured muscle (Fig. 14).52
of the 4. Injuries most often occur at the myotendi- Pure soft tissue injury of the tendon origin of
nous junction and most frequently involve the re- rectus femoris in adults is less common and there
flected head, where they are also known as is a paucity of published reports on it. In their retro-
central aponeurotic injuries.48 spective review of more than 3000 pelvic and hip
Rectus femoris tendon origin injuries, however, MR studies, Ouellette and colleagues52 found an
are far less common than myotendinous ones. overall incidence of 0.5% (17/3160); slightly more
Apophyseal injuries at the origin of rectus femoris than half their patients presented after trauma
 Tendon Injuries of the Hip 87

Fig. 14. (A) Axial oblique, (B) coronal, and (C) sagittal fat-suppressed PD-weighted postcontrast images in
a 26-year-old man who “fell 10 days ago.” There is a high-grade partial tear of the origin of the direct head
of rectus femoris (open arrows). (D) Axial and (E) coronal reformatted CT images 6 months later when the patient
returned for work-up of another condition. Heterotopic ossification has developed at the site of tendon tear
([D,E] open arrow).

and indirect head injuries outnumbered direct LATERAL PAIN AND THE PERITROCHANTERIC
ones. Rectus femoris origin injuries are also re- SPACE
ported to occur an average of once per season
in the National Football League, affecting both  Disorders of the hip abductor tendons
kicking and nonkicking positions.49 MR imaging  ESHS
findings include peritendinitis, tendinopathy, and Abnormalities of the peritrochanteric space were
tear (Figs. 14 and 15). under-recognized until the widespread use of hip
88 Petchprapa & Bencardino

Fig. 15. Axial (A) and sagittal (B) fat-suppressed intermediate-weighted images in a 42-year-old woman who
experienced a pop in her hip during dance class. There is a partial tear or the direct head of rectus femoris
from its origin (open white arrow).

arthroscopy. They are increasingly implicated as arises from the external iliac fossa and inserts on
common causes of lateral hip pain. Peritrochanter- the anterior facet of the greater trochanter
ic pathology falls into 2 major clinical diagnoses: (Fig. 16B). A second musculotendinous slip at-
greater trochanteric pain syndrome (GTPS) and taches to the ventral/superior aspect of the joint
ESHS. capsule. Gluteus minimus is a secondary hip
abductor and helps stabilize the femoral head in
Greater Trochanteric Pain Syndrome and the acetabulum.55 Gluteus medius has 2 distinct
Disorders of the Hip Abductor Tendons insertion sites (see Fig. 16C). The posterior muscle
fibers coalesce into a stout posterior tendon that
Previously known as greater trochanteric bursitis, inserts on the posterior facet; the central and ante-
GTPS is the preferred term for the spectrum of rior fibers form a rectangular muscular insertion on
abnormalities of the hip abductor tendons (gluteus the lateral facet. This tendon arrangement can be
medius and minimus) and peritrochanteric bursae. seen on far lateral sagittal MR images (see Fig. 16C).
In a study of more than 3000 adults, Sega and
colleagues53 found the prevalence of GTPS Imaging
17.6%, with higher prevalence in women and Axial/axial oblique images show the tendons to best
those with coexisting low back pain, osteoarthritis, advantage. On contiguous images, broad posterior
ITB tenderness, and obesity.54 gluteus medius tendon fibers coalesce into a stout
The most common presentation is that of tendon that inserts on the posterior facet. At the
chronic persistent lateral hip and/or buttock pain same level, central and anterior fibers form the
exacerbated by lying on the affected side, pro- predominantly muscular lateral facet insertion. The
longed standing, or transitioning to a standing greater trochanter has a smoothly curved postero-
position. Half of affected individuals complain of lateral surface on straight axial images at the inser-
lateral thigh pain that radiates to the knee. Patients tion of gluteus medius (see Fig. 16A).
are tender to palpation over the greater trochanter. The gluteus minimus insertion is more distal and
Because the hip abductors play an important role is located on the anteriorly-facing surface of the
in gait and hip joint stability, affected individuals anterior facet, identified by the angular lateral
can present with Trendelenburg gait as a result contour of the greater trochanter (see Fig. 3B).
of weak hip abduction. Because of the anterior facet’s orientation, the
trochanteric insertion of the gluteus minimus is
Anatomy rarely seen to advantage on the coronal images.
The peritrochanteric space is an anatomic space
between the ITB and the greater trochanteric Gluteus medius and minimus tendinopathy/
structures (hip abductor tendons and bursae). tear
Also known as the rotator cuff of the hip, the The abductor tendons can be affected by periten-
gluteus minimus and medius musculotendinous ditinitis (see Fig. 3), tendinopathy (see Fig. 3), and
units form a continuous soft tissue envelope over tendon tears (Fig. 17). Tendon pathology may or
the greater trochanter. Gluteus minimus broadly may not be accompanied by distension of
 Tendon Injuries of the Hip 89

Fig. 16. (A) Axial oblique PD-weighted image of the right hip shows the posterior insertion of gluteus medius
(open white arrow) and the tendon of gluteus minimus (white arrow) proximal to its insertion. (B) Axial oblique
fat-suppressed PD-weighted image caudal to A at the insertion of gluteus minimus (white arrow). (C) Sagittal fat-
suppressed PD-weighted image shows the insertions of gluteus minimus (white arrow) and both the lateral
(dotted arrow) and posterior (open white arrow) insertions of gluteus medius.

anatomic bursae located deep to and named for MR imaging had sensitivity of 33% to 100%,
their corresponding tendon. specificity of 92% to 100%, positive predictive
In a sonographic study of 75 patients with value of 71% to 100%, and negative predictive
GTPS, gluteus medius tendinosis manifested as value of 50% for the detection of hip abductor
tendon enlargement and diffuse echogenicity.56 pathology in a recent meta-analysis. Sonography
Tears most commonly affected the deep anterior had a sensitivity of 79% to 100% and positive
fibers of the lateral muscular insertion of gluteus predictive value of 95% to 100%.20
medius. Tendon gaps were frequently filled with This level of detail, however, is not always
fluid.56 possible on large FOV sequences of the pelvis
Tendon discontinuity on MR imaging can be de- and examinations done at lower field strengths,
tected and corroborated in multiple planes. As is where even tendon discontinuity can be undetect-
true in the shoulder, deep undersurface tears are able in the absence of significant tendon retraction.
not apparent during arthroscopy of the peritrochan- Secondary signs of tendon pathology become
teric space, and a comment about tear location is more important in this circumstance. Cvitanic and
helpful to arthroscopists; similarly the presence of colleagues57 found high T2 signal above the
muscle atrophy have implications in management greater trochanter larger than 1 cm or thin high T2
(see Fig. 5C). signal lateral and superior to the greater trochanter
90 Petchprapa & Bencardino

Fig. 17. (A) Coronal PD, (B) coronal fat-suppressed PD, and (C) sagittal fat-suppressed PD-weighted images in
a 46-year-old who woman who presented with atraumatic hip pain. The lateral trochanteric facet is bare
(brackets) due to a completely retracted tear of the lateral portion of gluteus medius.

to be the most specific secondary signs. High T2 anterior-posterior during hip and knee flexion and
signal had the greatest positive and negative extension (Fig. 18) and is subject to biomechanical
predictive value for abductor tendon tears. Elonga- forces as it traverses lateral to the greater
tion of the gluteus medius tendon greater than 2 cm trochanter at the hip and lateral to the lateral
in the coronal plane also proved helpful in the femoral condyle as it crosses the knee.
detection of tendon pathology. Coxa saltans externa, or external snapping hip,
GTPS is treated by rest, physical therapy, anti- is the most common of the 3 types of hip snapping.
inflammatory medications, and corticosteroid ESHS refers to painful catching of a pathologically
injections, which are successful in the vast thickened posterior third of the ITB or anterior
majority of patients. Open repair, particularly for edge of gluteus maximus as it translates anterior
full thickness tears, is an option in cases recalci- and posterior to the greater trochanter during hip
trant to conservative measures.58 Endoscopic flexion and extension. Patients may report
repair has emerged as a less-invasive treatment a subjective sensation of subluxation and disloca-
option requiring less rehabilitation and has been tion, leading some investigators to refer to this
associated with relief of pain and return of hip entity as pseudosubluxation.
abductor strength in small series.59 The cause of ITB thickening is likely multifacto-
rial but not completely understood. Although
symptoms may manifest after trauma, most are
External Snapping Hip Syndrome
associated with repetitive motions related to
The ITB is not a static structure. Its tension can be work or sport and have been reported in ballet
increased by contraction of gluteus maximus and dancers, cyclists, runners, and soccer players.60
tensor fascia lata.16 The ITB also translates ESHS is also reported after surgery where the
 Tendon Injuries of the Hip 91

Fig. 18. Anteroposterior translation of the ITB. When the hip is extended (A), the ITB (blue) and the margin of
gluteus maximus (red) are posterior to the greater trochanter (red star). As the hip is flexed (B), the ITB and
gluteus maximus translate anterior to the greater trochanter.

ITB was the source of graft, or when surgery contraction plays an important role in these
results in an overly prominent greater trochanter. injuries.
Coxa valga and reduced bi-iliac width are also Whereas concentric muscle contraction results
cited as potential predisposing conditions.61,62 in an increase in muscle tension coincident
Little has been written on the imaging findings of with muscle shortening (as occurs during the flexion
this entity. Pelsser and colleagues35 studied a small portion of a biceps curl), eccentric muscle contrac-
group of patients with sonography in whom half the tion results in an increase in muscle tension coinci-
snapping hips were painful. Although they demon- dent with muscle lengthening (as occurs during the
strated the dynamic aspects of this entity and their extension portion of a biceps curl). This serves to
association with pain under direct sonography, dissipate/store energy and absorb shock, which
they could not establish an association with are crucial in decelerating a limb or body segment.
increased ITB thickness and trochanteric bursitis. Generally, eccentric contractions generate greater
Treatment is conservative. Surgery is reserved loads than concentric ones; correspondingly
for recalcitrant cases and includes arthroscopic tendons of muscles, which participate in eccentric
release of the thickened tissue. contractions are subject to greater tensile loads.
In the case of the hamstring muscle group, eccen-
POSTERIOR PAIN tric contraction occurs during walking and running;
it decelerates the extended knee before foot strike,
 Disorders of the proximal hamstring tendons assists with hip extension after foot strike, then
 Hamstring tendinopathy extends the knee during the takeoff phase. If the
 Hamstring tendon tear forces needed to decelerate exceed the strength
of the myotendinous unit, the muscle, the myoten-
Posterior pain is less common than anterior, lateral,
dinous unit or the tendon can fail.
and medial pain63 and is most frequently secondary
The hamstring muscle group is most commonly
to lumbar spine disease or sacroiliac joint dysfunc-
injured at its weak myotendinous junction; this
tion. Proximal hamstring pathology, including ten-
most often affects the long head of biceps femo-
dinopathy and tendon rupture, is less commonly
ris.65 Myotendinous junction injuries are clinically
encountered. Gluteal/posterior thigh pain can
evaluated, treated conservatively, and generally
present a diagnostic challenge to clinicians, and
do well.
MR imaging is often enlisted for its work-up.64
Proximal hamstring tendinopathy is the result of
chronic repetitive eccentric overload.66 Also known
Disorders of the Hamstring Tendons
as hamstring syndrome, ischiatic intersection
Injuries to the hamstring myotendinous unit are syndrome, hamstring enthesopathy, high hamstring
common, particularly in athletes. Eccentric muscle tendinopathy, and hamstring origin tendinopathy,67
92 Petchprapa & Bencardino

this is commonly seen in running athletes and in is often necessary to make the diagnosis and
soccer and football players. define the extent of injury.
The most serious hamstring injuries are tendon
ruptures.68 They affect both the athletic and Anatomy
middle-aged nonathletic populations and are the The hamstring muscle group consists of semi-
result of voluntary or involuntary forceful eccentric membranosus, semitendinosus and the long
muscle contraction, as can occur when there is head of biceps femoris; together they play a role
sudden and simultaneous forced hip flexion and in knee flexion and hip extension and affect pelvic
knee extension. Excessive passive lengthening, tilt and rotation, sacral rotation and extension, and
seen in ballet dancers, is a less common cause. hip rotation.69
Surprisingly, distinguishing between myotendi- The hamstring muscles arise from the ischial
nous strain (treated conservatively) and tendon tuberosity, with the exception of the short head
rupture (potentially treated surgically) can be diffi- of the biceps femoris, which takes its origin from
cult. Approximately 25% of hamstring strength the lower lateral linea aspera at the midfemoral
comes from the short head biceps femoris; there- shaft and lateral supracondylar line of the femur.
fore, some hamstring strength may remain despite Semitendinosus and long head of the biceps
complete proximal tendon rupture. The presence femoris have a conjoint origin from the posterome-
of blood products may make palpation of a tendon dial aspect of the ischial tuberosity. Semimembra-
gap difficult on physical examination. MR imaging nosus arises from a long flat tendon at the

Fig. 19. Normal anatomy of the hamstring origin. (A) Coronal PD-weighted image shows the vertically oriented
origin of semimembranosus (white arrow). (B) Coronal PD-weighted image shows the oblique origin of the
conjoint biceps femoris and semitendinosus tendon, which points laterally (open white arrow). (C) Sagittal fat-
suppressed T2-weighted image shows semimembranosus tendon (white arrow) anterior to the conjoint tendon
(open white arrow).
 Tendon Injuries of the Hip 93

posterolateral aspect of the ischial tuberosity, into the popliteal fossa often suggests sciatic nerve
lateral to the conjoint tendon of the biceps femoris involvement,72 which can result in chronic pain if
and semitendinosus. scar forms around the secondarily involved nerve.
There is little information on the imaging of this
Imaging entity in the published literature. Zissen and
Although the hamstring origin consists of 3 struc- colleagues’ retrospective review of 65 patients
tures, on MR imaging, the origin of the hamstring treated by sonographic guided tendon injection73
muscle complex is dominated by the appearance revealed peritendinitis (63%) as the most common
of 2 tendons—those of semimembranosus and preinjection MR imaging finding. Tendinopathy
biceps femoris. was seen in 25%, and no tendon abnormalities
The 2 can be distinguished in the coronal plane; were seen in 22%. Of the 3 tendons, semimembra-
whereas the semimembranosus tendon is vertically nosus is the most commonly affected.64 De Smet
oriented at its origin (Fig. 19A), the biceps femoris and colleagues13 found that symptomatic patients
tendon points lateral toward its ultimate distal inser- were more likely to have a thickened tendon, peri-
tion at the fibula (see Fig. 19B). In the sagittal plane, tendinous increased T2 signal, and reactive
the semimembranosus tendon is located anterior edema of the ischial tuberosity, although there
and lateral to the conjoint (see Fig. 19C). was considerable overlap between symptomatic
In contrast, the semitendinosus origin is predom- and asymptomatic patients with regards to the
inantly muscular; its small tendon seen may not be presence of signal abnormality.
appreciated on MR imaging. Semitendinosus arises Anti-inflammatory medications and physical
from the medial surface of the long head biceps therapy are successful in the majority of patients.
femoris tendon and from the ischial tuberosity.70 Semimembranosus tenotomy is considered when
conservative management fails.64
Hamstring Tendinopathy
Hamstring Tendon Tear
High hamstring tendinopathy (see Fig. 4) is an
uncommon overuse injury seen in young athletes Proximal hamstring tendon avulsions are common
involved in sports that require bursts of speed and in adult football players, runners, water skiers,
repetitive hip stretch, such as football, soccer, cheerleaders, gymnasts, and dancers. These
basketball, sprinting, rowing, and kickboxing. most commonly occur at their origin, and most
Patients typically report deep buttock or thigh pain frequently affect the conjoint tendon with variable
when running and when seated.71 Pain radiating involvement of semimembranosus. In contrast to

Fig. 20. (A) Coronal and (B) sagittal STIR and (C) axial fat-suppressed T2-weighted images in a 50-year-old man who
presented after water-skiing injury. The ischial tuberosity is bare ([A and C] white bracket) where the tendons were
avulsed and retracted ([A] open white arrow). Note the extensive edema along the length of the sciatic nerve
(black bracket).
94 Petchprapa & Bencardino

children, in whom osseous avulsions are common, 9. Yang I, Hayes CW, Biermann JS. Calcific tendinitis of
adult injuries are often soft tissue (Fig. 20). Patients the gluteus medius tendon with bone marrow edema
report a pop or snap; this is followed by posterior mimicking metastatic disease. Skeletal Radiol 2002;
thigh pain, weakness, and sensation of giving 31(6):359–61.
away and avoid sitting on the affected side 10. Flemming DJ, Murphey MD, Shekitka KM, et al.
because of pain. Osseous involvement in calcific tendinitis: a retro-
The role of imaging is to confirm the diagnosis and spective review of 50 cases. AJR Am J Roentgenol
evaluate the extent of the disease. Although there is 2003;181(4):965–72.
some variation among practitioners, most agree that 11. Hottat N, Fumière E, Delcour C. Calcific tendinitis of
single tendon ruptures and multitendon ruptures re- the gluteus maximus tendon: CT findings. Eur Radiol
tracted less than 2 cm may be treated conserva- 1999;9(6):1104–6.
tively74 because torn tendons tend to scar to intact 12. Blankenbaker DG, Ullrick SR, Davis KW, et al. Corre-
tendons, allowing for return to full strength. lation of MRI findings with clinical findings of
trochanteric pain syndrome. Skeletal Radiol 2008;
37(10):903–9.
SUMMARY
13. De Smet AA, Blankenbaker DG, Alsheik NH, et al.
Tendon pathology is a common cause of hip pain MRI appearance of the proximal hamstring tendons
but can be difficult to diagnose by physical exam- in patients with and without symptomatic proximal
ination. Imaging, in particular MR imaging, is inte- hamstring tendinopathy. AJR Am J Roentgenol
gral in the work-up because of its ability to 2012;198(2):418–22.
evaluate both the hip joint and its surrounding 14. Micheli LJ, Fehlandt AF Jr. Overuse injuries to
tendons. An anatomy-based search process can tendons and apophyses in children and adoles-
facilitate MR imaging interpretation and ensure cents. Clin Sports Med 1992;11(4):713–26.
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differential diagnosis of nonarthritic hip pain. band syndrome: what is it and where is it? Skeletal
Radiol 2011;40(12):1553–6.
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