Joint Motion

Range of Motion:
The normal Range of motion (ROM) of a joint is sometimes called the anatomic
or physiologic ROM, referring to the amount of motion available to a joint with
in the anatomic limits of the joint structure.
The Extent of the anatomic range is determined by a number of factors,
including the shape of the joint surfaces, the joint capsule, ligaments, muscle
bulk, and surrounding musculotendinous and bony structures.
The sensation experienced by the examiner performing passive physiologic
movements at each joint is referred to as the end-feel.
A ROM is considered to be pathological when motion at a joint either exceeds
or fails to reach the normal anatomic limits of motion. When a ROM exceeds
the normal limits, the joint is hypermobile.
When the ROM is less than what would normally be permitted by the structure,
the joint is hypomobile.
Hypermobility may be caused by a failure to limit motion through bony
elements or soft tissues, including weak musculature, leading to instability.
Soft tissues connect, support, and surround the different body organs. They can
be found in most parts of the body. Soft tissues include fat, muscle, nerves,
blood vessels, ligaments, tendons.
Hypomobility may be caused by bony or cartilaginous blocks to motion or by
the inability of the capsule, ligaments, or muscles to elongate sufficiently to
allow a normal ROM.
A contracture, which is the shortening of soft tissue structures around a joint,
is one cause of hypomobility.
A condition of shortening and hardening of muscles, tendons , or other tissue,
often leading to deformity and rigidity of joints.

Contractures occur when the burn scar matures, thickens, and tightens,
preventing movement.
Osteokinematics :
Osteokinematics refers to the rotary movement of the bones in space during
physiological joint motion. These are the observable movements of the bony
levers in the sagittal, frontal, and transverse planes that occur at joints.
Visible movements.
One segment is moving and the other segment is stationary.
It has a direction of movement. For example shoulder flexion happens in X axis
and in sagittal plane.
Osteokinematic movements at the knee joint include flexion or extension of the
tibia on the femur (or the femur on the tibia) in the sagittal plane about a coronal
axis.

Physiological joint motion involves rotation of bony segments

(osteokinematics) as well as motion of the joint surfaces in relation to another.
Movements between adjacent joint surfaces accompany voluntary
osteokinematic movement but cannot be voluntarily isolated under normal
conditions.
Arthrokinematics :
The Movement of Joint surfaces.
One common example of the application of the convex-concave rules is the
arthrokinematics of abduction of the glenohumeral(GH) joint the convex
humeral head rolls superior relative to the glenoid fossa as a point on its
articular surface simultaneously slides inferior.
The term arthrokinematics, or accessory motion, is used to refer to these
movements of joint surfaces relative to one another. Often, one of the joint
surfaces is relatively stable and serves as a base for the motion, whereas the
other surface moves on this relatively fixed base. The terms roll, slide or glide
and spin are used to describe the type of motion that the moving part performs.
Rolling : In Rolling movement new points of moving segment comes in contact
with the same point of the stationary segment.
Gliding : A same point comes in contact with the articular surfaces.

Spin :
 Movement is produced by the head of the radius rotating within the annular
ligament.
There are two movements possible at this joint; pronation and supination.
Pronation: Produced by the pronator quadratus and pronator teres. Supination:
Produced by the supinator and biceps brachii.
Axis :An axis is a straight line around which an object rotates. Movement at the
joint takes place in a plane about an axis. There are three axes of rotation.

● Sagittal axis - passes horizontally from posterior to anterior and is

formed by the intersection of the sagittal and transverse planes.
● Frontal axis - passes horizontally from left to right and is formed by
the intersection of the frontal and transverse planes.
● Vertical axis - passes vertically from inferior to superior and is formed
by the intersection of the sagittal and frontal planes.

Planes in human body:

A plane is an imaginary flat surface running through the body.
● Coronal (frontal) plane: separates the front (anterior) and back (posterior) of the
body.
● Sagittal (longitudinal) plane: separates the left and right sides of the body.
● Transverse (axial) plane: separates the upper (superior) and lower (inferior)
halves of the body.
For articular surfaces to be free to move in the appropriate direction
(arthrokinematics) as the bony lever rotates (osteokinematics), the joint must
have a certain amount of “joint play.”
This freedom of movement of one articular surface on another can be tested by
an examiner when the joint is in a loose-packed position.
 Joint Play is a fundamental aspect of physical therapy, defined as the passive
movement occurring between joint surfaces. This biomechanical phenomenon
allows for the assessment and treatment of joint dysfunctions, ranging from
hypomobility to hypermobility. Joint Play comprises various types of
movements such as gliding, spinning, rolling and distraction. These movements
are integral in maintaining the health and functionality of a joint.

Notably, Joint Play contributes to overall joint mobility – an indispensable

factor in human locomotion. It influences factors like range of motion (ROM),
flexibility and stability within a joint. Physical therapists often manipulate these
intrinsic movements during manual therapy to alleviate pain, improve mobility
or rehabilitate after an injury.

From an anatomical perspective, Joint Play is largely determined by the shape

and congruency of articulating surfaces, the laxity of surrounding ligaments and
capsule, and the tone of periarticular muscles. The understanding and
application of Joint Play principles are cornerstones in orthopedic physical
therapy.

The joint should have a sufficient amount of play to allow normal motion at the
joint’s articulating surfaces. If the supporting joint structures are excessively
lax, the joint may have too much play and become unstable.
If the joint structures are excessively tight, the joint will have too little
movement between the articular surfaces, and movement of the bony lever will
be restricted because the appropriate intra-articular movement will not
accompanythe physiological movement.
Close-packed position
The joint's concave surface is completely congruent with the convex surface, and the
joint surfaces are tightly compressed. The capsule and ligaments are under maximal
tension, and the two bones of the articular unit cannot be separated.
Loose-packed position
The joint is under the least amount of stress, and the capsule is most relaxed. The area
of contact and joint stability is reduced. The loose-packed position is also called the open
packed position.
Disease, injury, immobilization, exercise, and overuse can cause a variety of
changes to the body, including:
Each part of a joint has one or more specific functions that are essential for the
overall performance of the joint.
Therefore, anything that affects one part of a joint will disrupt the total function
of the joint. Likewise, anything that affects all the structures that constitute that
joint.
This relationship between form and function is essential for therapists to
remember during rehabilitation after injury. For example, when a bone is
broken , the fracture may be the main injury that dictates subsequent treatment,
but lack of motion and decreased loading also will affect cartilage, ligaments,
joint capsule, tendons, and muscles.
The ideal rehabilitation protocol considers the behaviour of all the affected
structures and includes interventions designed to induce changes in each
structure.
This means understanding the time course and nature of the adaptation of each
tissue to altered loading conditions.
Complex joints are more likely to be affected by injury, disease, or aging than
are simple joints.
Complex joints have more parts and are subject to more wear and tear than are
stability joints. The function of the complex joints depends on a number of
interrelated factors. For example, the capsule must produce synovial fluid,
which must be of the appropriate composition and of sufficient quantity to
lubricate and nourish the joint.
The hyaline cartilage must be smooth enough that the joint surfaces can move
easily, yet permeable enough to receive nourishment from the joint fluid.
The capsules and ligaments need to be flexible enough to allow for normal joint
motion while also being strong enough to offer enough support for stability.
Tendons must be able to withstand the forces generated by muscles as they
produce movement.
Disease:
The general effects of disease, injury, immobilization and overuse may be
illustrated by using the normal function of a joint structure as a basis for
analysis. For example, when the synovial membrane of a joint is affected by a
disease like rheumatoid arthritis, the production , and perhaps the composition,
of the synovial fluid changes. Lubrication of the joint is also affected. The
disease process and the changes in joint structure that occur in rheumatoid
arthritis involve far more than just synovial fluid alteration, but the disease does
change the composition and the quantity of the synovial fluid.
In another type of arthritis, osteoarthritis, which may be genetic and/or
mechanical in origin, the cartilage is the focus of the disease process.
Erosion and splitting of the cartilage occur. As a result, friction is increased
between the joint surfaces, thus further increasing the erosion process.
Injury:
Joint support is decreased after injury to one or more of its components.

If a table has an unstable joint between a leg and the table top, damage and
disruption of function may occur as a result of instability. If heavy load is
placed on the damaged table joint, the joint surfaces will separate under the
compressive load and the leg may be angled.
The once stable joint now allows mobility, and the leg may wobble back and
forth. This motion may cause screws to loosen or nails to bend and ultimately to
be torn out of one of the wooden components.
complete failure of the table joint may result in splitting of the wooden
components, especially if the already weakened joint is subjected to excessive,
sudden, or prolonged loads. The effects of decreased support in a human joint
are similar to those in the table joint. Separation of the bony surfaces occur and
may result in wobbling or a deviation from the normal alignment of the bony
components. Other ligaments, tendons and the joint capsule may be subjected to
increased loading, leading them to become excessively stretched and unable to
provide protection.
 According to Van Osch and colleagues, joint instability is a well known cause
of secondary osteoarthritis involving the knee joint.
The recognition that joint injuries, especially ligament injuries, lead to
osteoarthritis suggests greater efforts are required to prevent and treat sport
injuries in young people.
● Immobilization :
● Immobilization is particularly harmful to joint structure and function.
Immobilization may be externally imposed by a cast, bed rest, weightlessness, or
denervation or may be self imposed as a reaction to pain and inflammation.
● An injured joint subjected to inflammation and swelling will assume a loose-packed
position to accommodate the increased volume of fluid with in the joint space. This
position may be referred to as the position of comfort because pain is decreased in
this position.
● Each joint has a position of minimum pressure and maximum volume. For the knee
and hip joints, the position of comfort is between 30 degrees and 45 degrees of
flexion; for the ankle joint, the position is at 15 degrees of plantar flexion.
● If the joint is immobilized for a few weeks in the position of comfort, the joint
capsule will adapt (shorten), and contractures will develop in the surrounding soft
tissues. Consequently, resumption of a normal range of motion will be difficult.
Increased and decreased loads on connective tissue can have different
effects, including:
● Increased load :
Physical activity can increase the strength and mass of connective tissue. This
can happen through changes in the material properties of the tissue, such as
increased collagen content or collagen crosslinking. It can also happen through
an increase in the cross-sectional area of the tissue.
● Decreased load :
De-tensioning of skeletal muscle in a shortening position can decrease the
enzymatic activity of collagen synthesizing enzymes.
● Excessive or insufficient load :
Excessive or insufficient mechanical loading can lead to tendon
injuries. Natural tendon healing is often insufficient, and can lead to improper
collagen fibril distribution and misalignment.

● EFFECTS ON LIGAMENT AND TENDON :

Ligaments and tendons adapt to decreased load by decreasing their collagen
content and reducing cross-linking among collagen molecules, although their
 overall size may remain the same. As a result, the tissue becomes weaker, and
returning to previously typical loading may result in more stress and strain.
● Ligaments and tendons show a 50 percent decrease in tensile strength and stiffness
after 8 weeks of immobilization. In general, the time course for the loss of
mechanical properties occurs over weeks, where as recovery can take 12 to 18
months or more.
● Gradual reloading is necessary to restore tendon and ligament strength.
● Effects on Articular surfaces and Bone :
● The effects of immobilization are not confined to the surrounding soft tissues but
may also affect the articular surfaces of the joint and the underlying bone.
● Biochemical and morphological changes may include : proliferation of fibrofatty
connective tissue with in the joint space, adhesions between the folds of the
synovium, atrophy of cartilage, regional osteoporosis, weakening of ligaments at
their insertion sites as a result of osteoclastic resorption of bone and sharpeys fibers,
a decrease in the PG content, and increase in the water content of articular cartilage.
● . Sharpey's fibers, also known as perforating fibers or bone fibers, are bundles of
collagen fibers which connect periosteum to bone. They originate in the periosteum
and penetrate deeply into the bone matrix, anchoring the periosteum to the
underlying bone.

● The water content of articular cartilage is between 60% and 80% by weight. The
water content of articular cartilage decreases with age, but may increase before the
onset of osteoarthritis.
● As a result of changes in joint structures brought about by immobilization,
decreases may be evident in the ROM available to the joint. swelling or
immobilization of a joint also inhibits and weakens the muscles surrounding the
joint.
● Recognition of adverse effects of immobilization has led to the development of
several strategies to help minimize the consequences of immobilization :
● 1. Use of continuous passive motion ( CPM) devices after joint surgery.
● 2. Reduction in the duration of casting periods after fractures and sprains,
● 3. Development of dynamic splinting devices to allow joint motion while
preventing un wanted motion that may damage healing structures.
● 4. Use of graded loading after immobilization, and
● 5. Extension of the recovery period to months rather than days or weeks.
The continuous passive motion device can move joints passively and repeatedly
through a specified portion of the physiological ROM.
The speed of the movement and ROM can be controlled.
Continuous passive motion was shown to prevent some of the tendon weakening
that occurs during immobilization.
Exercise:
All tissues appear to respond favourably to gradual progressive loading by adapting
to meet increased mechanical demands.
Exercise influences cell shape and physiological functions and can have a direct
effect on matrix alignment.
The response to exercise varies among tissues and depends on the nature of the
stimulus, including the amount, type, and frequency of loading.
The mechanism of connective tissue response to exercise appears to involve cells
detecting tissue strain and then modifying the type and amount of tissue they
produce.
Low-frequency compressive loading will increase cartilage formation, whereas
higher frequencies can enhance bone synthesis.
Higher magnitude or sustained loading will induce fibro cartilage formation, where
as tensile loads induce tissue formation resembling that found in tendon or
ligament.
According to Mueller and Maluf’s physical stress theory, maintaining the normal
mechanical state of connective tissues appears to require repetitive loading beyond
a threshold level.
Bone response to Exercise:
Bone deposition is increased with weight-bearing exercise and in areas of bone
subjected to increased muscle force. This response of bone form to function,
Wolff’s law, has been known for over 100 years, and exercise is now used as a
therapeutic intervention to prevent bone loss.
Bone formation appears very sensitive to strains as well as the magnitude of the
applied load. Very low magnitude high-frequency vibration has been shown to
increase trabecular bone formation by 34%.
 Even short durations of loading are effective, and just 10 minutes of low load, high
frequency stimulation has been shown to prevent bone loss induced by disuse.
Each exercise session should include as many novel strain distributions as possible,
preferably involving high peak strains and strain rates.
Cartilage response to Exercise:
The response of cartilage to immobilization has been described, but its response to
increased physiological loading is largely unknown. Cartilage thickness increases
after long duration exercises like running and cycling.
The health of articular cartilage depends on the application and removal of
compressive loads.
Chondrocytes are directly connected to their micro environment through
attachments between cell membrane proteins(integrins) and collagen fibrils, and
mechanical forces are transduced in to intracellular synthetic activity.
The mechanisms of this transduction and the magnitude and frequency of the
loading that will optimize cartilage structure are not yet known.
This is an area of active research, as cartilage injuries heal very poorly, and the use
of transplanted material to repair cartilage defects is being explored.

● Overuse injuries
These are a common cause of athletic injuries and can affect many parts of the
body, including bones, muscles, tendons, ligaments, and cartilage. Overuse
injuries are caused by repetitive stress on the body, and can be caused by
increasing the intensity or length of workouts too quickly.
Stress:
Stress is a force exerted on a material per unit area.
The force applied to a material per unit area (

𝑆=𝑅/𝐴
S=R/Acap S equals cap R / cap A

𝑆
, where

𝑅
is stress,

𝐴
is the resisting force, and
is the cross-sectional area). Stress is measured in megapascals (MPa).

● Strain

The relative change in the material's length or shape (

Strain=change in length /original lengthcap S t r a i n equals c h a n g e i n l e n g t h /

originallength

𝑆𝑡𝑟𝑎𝑖𝑛=𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑙𝑒𝑛𝑔𝑡ℎ/𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑙𝑒𝑛𝑔𝑡ℎ

). Strain is a measure of how a material reacts to being loaded.

● Stress-strain curve
● A stress strain curve is a graph that shows how stress changes as strain increases in a
material.

A graph that plots stress on the y-axis and strain on the x-axis. The curve can help
determine the properties of a material.

Examples

● Muscles carrying a load: The muscles are under strain because they are resisting
changes in position due to the weight they are carrying.
● Tendon tensile strength: The tensile strength of a tendon depends on the collagen it
contains.
● Fibrocartilage: Fibrocartilage is found in areas of the body that withstand repeated
high-level stress, such as when biting or chewing.

Understanding stress and strain can help prevent injuries and treat injuries to tissues like
tendons, ligaments, and bones.
Load is stress and deformation is strain.
Whenever the external force is applied to soft tissue it goes for more stress and
strain.
The first phase is elastic phase where the stretched tissue will go for normal
position after removing the external force.
The second phase is plastic phase where the stretched tissue may remain elongated
state when external force is removed.
Third phase is failure point where the stretched tissue may be teared or separated.
Normally joint mobilization techniques are done up to limit of plastic phase.
Hooke’s Law:
Stress and strain of a elastic material are directly proportional to each other.
When the elastic materials are stretched, the atoms and molecules deform until
stress is applied, and when the stress is removed, they return to their initial state.
Wolff's law states that bones adapt to the amount of mechanical stress they
experience. This means that bones will remodel themselves over time to become
stronger when the loads on them increase.
Osteoblasts, osteoclasts, and osteocytes are all types of cells in bone that contribute
to bone homeostasis, but they have different functions:
Osteoblasts: Form bone tissue.
Osteoclasts: Break down bone tissue.
Osteocytes: Mature bone cells that act as mechanosensors and orchestrate bone
remodeling.
Materials found in Human Body :
Structure of a Connective tissue :
Connective tissue is characterized by widely dispersed cells and a large volume
of extra cellular matrix.
In biology, matrix ( pl. : matrices) is the material (or tissue) in between a
eukaryotic organism's cells. The structure of connective tissues is an
extracellular matrix.
Matrix is the ground, non-living, medium or substance of the tissue that
occupies the vacant spaces between the cells. It is particularly referred to as
the extracellular matrix.
Eukaryotes have a nucleus and membrane-bound organelles, while
prokaryotes do not.
Membrane-bound organelles are organelles in a cell that are surrounded by a
membrane.
Examples of eukaryotes include animals, plants, fungi while examples of
prokaryotes include bacteria
Integrins are proteins that help cells attach to other cells and the extracellular
matrix (ECM).