ELBOW BIOMECHANICS
Dr Payal Dhawale
Dept. Of Sports Physiotherapy
MGM Institute Of Physiotherapy
Chh. Sambhajinagar
●The joints & muscles of elbow complex
serve an important role to provide mobility
as well as stability function for the hand
●Uniaxial diarthrodial joint of hinge type with
1 degree of freedom of motion
●The elbow complex includes the elbow
joint (humeroulnar and humeroradial joints)
and the proximal and distal radioulnar
joints elbow and forearm respectivily.
Bone
Articulating Surfaces –
1. Humeroulnar jt.
● Concave trochlear notch of ulna
● Convex trochlea of humerus
2. Humeroradial jt.
● Conave Fovea of head of radius
● Convex Spherically shaped capitulum
Lateral and anterior veiw
A
Joint capsule
√ The Capsule is large ,loose and weak
anteriorly but ligaments reinforce from its
sides
√ Attachments - anterior, posterior, medial,
lateral
Ligaments :
2 main ligaments –
●Medial Collateral Ligament
●Lateral collateral Ligament
●The elbow joint is considered to be a
compound joint that functions as a
modified or loose hinge joint.
●One degree of freedom is possible at the
elbow, permitting the motions of flexion
and extension,
●which occur in the sagittal plane around a
coronal axis.
●A slight bit of axial rotation and side-to-side
motion of the ulna occurs during flexion
and extension, and that is why the elbow is
considered to be a modified or loose hinge
joint rather than a pure hinge joint.
●Two major ligaments and five muscles are
directly associated with the elbow joint.
●Three of the muscles are flexors that cross
the anterior aspect of the joint.
●The other two muscles are extensors that
cross the posterior aspect of the joint.
●Extension – triceps brachii and anconeus
●Flexion – brachialis, biceps brachii,
brachioradialis
Ligaments
1. Medial Collateral Ligament
3 parts –
a. Anterior
b. Posterior
c. Transverse/Oblique
●Anterior Fibers :strongest
& stiffest
Arise from anterior aspect of medial
epicondyle & insert on medial part of
coronoid process of ulna
Consists of 3 anatomically & functionally
distinct fibers based on proximal
attachment
Fibers arising from anterior surface of
medial condyle – taut in full extension
Fibers arising from below tip of medial
epicondyle – taut in 90° flexion to full
flexion
Fibers arising from inferior edge of medial
epicondyle – always taut throughout full
ROM
Anterior portion of the MCL is considered to
be the primary stabilizer of the elbow to
valgus stress in the range of elbow flexion
from 20-120 deg of flexion
Primary restraint to valgus at 30°, 60°, and
90°of flexion
Coprimary restraint to valgus at 120° of
flexion
Posterior Fibers :
● Attachment –
Originate - Posterior part of medial
epicondyle
Insert - Medial margin of olecranon &
coronoid process
● Primary restraint to valgus at 120° of flex &
secondary restraint at 30° & 90° of flexion
● Function –
● Becomes taut in extremes of elbow flexion & so
limits extension
● Prevents posterior translation of radial head
Transverse Fibers :
Cross from olecranon to coronoid process of
ulna
Since they originate & insert on same bone ,
they don’t provide significant articular
stability
Lateral Collateral ligamentous
complex :
Lateral Radial Collateral Ligament
Lateral Ulnar Collateral Ligament
Annular Collateral Ligament
●Originates on lateral epicondyle &
immediately splits into 2 fiber bundles
●Fan shaped
●That extend from inf aspect lateral
epicondyle of the humerous to merge with
the annular ligament
FIBER STABILIZATION
●MCL
●All fibers stabilize against the valgus stress
at elbow
●LCL
●All fibers stabilize against the varus stress
at elbow
Kinematics
● One degree of freedom
● Flexion: 135 to145°
● Passive flexion: 150 to 160
● Extension: -5° (hyperextension)
● Functional Range: 30-130°
● Carrying angle
■ Males – 0-5 deg
■ Females - 10-15 deg
Cubitus valgus/varus
Axis of motion
● Axis of motion
Axis for flexion & extension is relatively
fixed & passes through the centre of
trochlea & capitulum bisecting the
longitudnal axis of shaft of humerus
Arthrokinematics
At Humeroulnar jt
Flexion –
Concave surface of trochlear notch rolls
& slides anteriorly on convex trochlea
Full pasive elbow flexion requires elongation
of the Posterior capsule, extensor ms,
ulnar nerve, post fibres of MCL
Extension - vice versa
Arthrokinematics
●At Humeroradial jt
There is rolling & sliding of fovea of radius
across convexity of capitulum
●Provides minimal structural stability to
elbow jt ,however, provides an imp bony
resistance against a valgus force
Elbow Muscles
Functions of elbow muscles :
A. Elbow flexors
Role of elbow flexors is determined by number
of factors –
● Location of muscles
● Position of elbow & adjacent joints
● Position of forearm
● Magnitude of applied load
● Speed of motion
● Type of muscle contraction
Brachialis
● Mobility ms – insertion close to jt axis
●Average
2,
physiologic cross-section of 7
cm the largest of any ms crossing the
elbow – generates the greatest force of
any ms crossing the elbow, so active in all
types of contraction
●Work horse of elbow flexion as it is active
in all positions ,all speeds & against
maximal /minimal resistance
●MA is greatest at slightly > 100 of elbow
flexion
●Not affected by change in position of
forearm / shoulder, so active in all positions
Biceps Brachii
● Mobility ms – insertion close to0 jt axis
● MA is largest between 80 -100 of elbow flexion
● In full elbow extension msl force is compressive
● Beyond 100 flexion , acts as a distracting force
● Affected by change in position of shoulder &
elbow
Brachioradialis
●Inserted away from jt axis-stability ms
●Peak MA occurs between 100- 120 of elbow
flexion
●More active in midprone position
●Not affected by change in position of forearm/
shoulder
●Maximal torque produced by elbow flexors :
depends on 2 factors –
●Muscles maximal flexion force potential eg.
Brachialis
●Internal moment arm length eg. elbow flexion
with forearm in supination
Elbow extensors
1. Triceps Brachii
2. Anconeus
st
● Anconeus usually 1 to initiate & maintain low
level extension forces
● Next , medial head of triceps followed by lateral
head & long head of triceps
● Medial head – work horse of extensors
● Long head – Reserve elbow extensor
●Effectiveness of triceps is affected by
change in position of shoulder but not by
changes in position of forearm
●Maximal isometric torque is generated
at elbow 90 flexed
●Effectiveness of triceps is affected by
change in position of shoulder but not by
changes in position of forearm
●Maximal isometric torque is generated
at elbow 90 flexed
Radioulnar joints
●The radioulnar joints are two locations in
which the radius and ulna articulate in the
forearm:
●Proximal radioulnar joint
●Distal radioulnar joint
●Proximal radioulnar joint: This is located
near the elbow, and is an articulation
between the head of the radius, and the
radial notch of the ulna.
●Distal radioulnar joint: This is located near
the wrist , and is an articulation between
the ulnar notch of the radius, and the ulnar
head.
●Both of these joints are classified as pivot
joints, responsible for pronation and
supination of the forearm.
Proximal radioulnar joint :
●Articulating surfaces –
- Concave radial notch
- Head of radius
- Annular ligament
- Capitulum of humerus
Distal Radioulnar joint :
●Articulating surfaces –
- Ulnar notch of radius
- Head of ulna
- Articular disk
