biomechanics of joints

1. BIOMECHANICS OF JOINTS
SONALI VISPUTE
MPT 1ST YEAR
COMMUNITY MEDICAL SCIENCES

2. CONTENTS
 Classification of Human Joints
 Structure of Human Joints
 Properties of Connective tissue
 Classification of Joint Motion: 1. Osteokinematics
2. Arthrokinematics
 Factors influencing motion at a joint and its clinical
relevance
 General changes with disease, injury, immobilization,
exercise and overuse

3. Classification of Human Joints
SYNARTHROSES DIARTHROSES
Fibrous Joints Cartilaginous Joints
Sutures Gomphoses Syndesmoses
Symphyses Synchondroses

4. SUTURES

5. SYNDESMOSES

6. SYMPHYSES AND SYNCHONDROSES

7. DIARTHROSES
Anatomical Classification Example
Hinge Distal interphalangeal joint
Pivot Superior radioulnar joint
Condyloid Metacarpophalangeal joint of
the fingers
Ellipsoid Wrist (radiocarpal) joint
Saddle Carpometacarpal joint of the
thumb
Ball and Socket Glenohumeral joint
Plane Joints between carpal bones

8. STRUCTURE OF JOINTS
Diarthroses Synarthroses
-Joint Capsule -Fibrous connective tissue
-Joint Cavity -Cartilaginous connective tissue
-Synovial tissue
-Synovial fluid

9. SYNOVIAL CAPSULE:
-A sac composed of fibrous and synovial membranes that
surrounds a joint.
-e.g., Adhesive capsulitis: shoulder capsule thickening
SYNOVIAL FLUID:
-Produced by the synovial membrane and contained within
the joint capsule.
-It aids joint lubrication.
-Compression and distraction of joint surfaces occur
during weight bearing and active movements allows
diffusion of nutrients.

10. JOINT LUBRICATION:
-Reduces the friction between the articular cartilage of
synovial joints during movement.
-e.g., In osteoarthritis, there is thinning of synovial fluid
causes irritation and inflammation of synovial membrane.

11. A Typical Diarthrodial Joint

12. Properties of Connective Tissue
1) Mechanical Behaviour
-Load, Force and Elongation
-Stress and Strain
-Load Deformation and Stress-strain Curve
-Young’s Modulus
2) Viscoelasticity and Time-dependent and Rate-dependent
Properties
-Creep
-Stress-Relaxation
-Hysteresis
-Strain-Rate Sensitivity

13. Mechanical Behaviour
 Load, Force and Elongation
Load: Force or forces applied to a structure
Force: A push or a pull exerted by one object or
substance on another.
Deformation: When a force acts on an object,
produces deformation.
Elongation: A tensile load produces elongation.
Compression: A compressive force produces
compression.

14.  Stress and Strain:
Stress: The force per cross-sectional unit of
material.
S = F / A.
Strain: The percentage change in the length
or cross-section of a structure or material.
Strain = (L2 – L1) / L1

15. Types of Loads
1) Tensile loading
2) Compressive loading
3) Shear loading

16. Load Deformation Curve
- Result of plotting the applied load against
the deformation.
- Strength properties of a particular
structure.

17. Stress-strain Curve
-A typical curve for tendons and ligaments.

18. Young’s Modulus
-Measure of the material’s stiffness.
-Inverse of stiffness is compliance.
e.g., High modulus of elasticity: cortical bone
Low modulus of elasticity: subcutaneous fat

19. Viscoelasticity
 Viscosity is material’s resistance to flow
 High viscosity- High resistance to deformation
 Low viscosity- Low resistance to deformation

20. Time-Dependent and Rate-
Dependent Properties
1. Creep:
Connective tissue elongate
after an initial elastic
response to a constant
tensile load and gradually
return to original length
after load is removed.

21. 2.Stress-Relaxation:
If a tissue is stretched to
a fixed length while the
force required to
maintain this length will
decrease over time.

22. 3. Hysteresis:
As the tissue is stretched to a fixed length and held
there, some energy is dissipated through tissue
elongation as heat.

23. 4. Strain-Rate Sensitivity:
Fast loading More force required to deform
the tissues.
Slow loading Less force required to deform
the tissues.

24. Classification of Motion
1. TRANSLATION 2. ROTATION

25. OSTEOKINEMATICS
- Rotary movement of bones in space during
physiological joint motion.
- E.g., Knee joint: Flexion and Extension of the
tibia on the femur in the sagittal plane and
coronal axis.

26. ARTHROKINEMATICS
Movement of adjacent Joint surfaces.
1) Slide
2) Spin
3) Roll

27. Clinical Relevance
Joint Mobilization:
-Manual therapy to restore the joint glides
necessary for joint ROM.
-Based on the arthrokinematics of that joint.
-e.g., to increase knee flexion and extension
ROM, anterior and posterior glides of the tibia on
femur can be given.

28. CONVEX-CONCAVE Joint Surface Motion
Convex moving on concave=opposite direction
Concave moving on convex=same direction

29. Clinical Relevance
-If downward
gliding restricted,
abduction of
humerus may cause
impingement of
superiorly located
soft tissue between
humerus and the
acromion.

30. Factors influencing motion at a Joint:
1) Effect of Joint Structure on joint motion:
-Joint surfaces
-Ligamentous support
2) External forces on a joint
3) Interactions between joints and the External
Environment

31. Factors influencing motion at a joint

32.  The effect of Joint Structure on Joint motion:
1) Joint Surfaces
-Shapes of articular surfaces:
More congruent articulation restrain
motion more stable
Less congruent articulation more mobility

34. -Amount of curvature of surfaces of articulating
surfaces:
Radius of curvature
More curved surface smaller the R.O.C.
Flat surfaces- allows translation
More curved surfaces-allows rotation

35. Clinical Relevance
The Knee Joint:
Four articulating surfaces between the femur and
tibia with different radius of curvature
Produce combination of rotation and translation
Accompanies knee flexion and extension

36. 2) Ligamentous support:
-It influences mobility and stability.
-Synovial joint capsule have folds unfold as
capsule stretched to allow more joint movement.
-e.g., a) Inferior portion of GH joint capsule lies
in folds when shoulder is in neutral position, unfolds
during shoulder flexion and abduction.

37. b) collateral ligaments on medial and lateral
sides of a joint provides stability and limiting side to
side movement.

38. Clinical Relevance
 GH joint stability:
-Inferior subluxation of GH joint
-most frequently in severe muscle weakness
-when shoulder is in neutral
-folded inferior GH joint capsule unable to
stabilize the joint

39. External forces on a Joint
 The weight of the limb
 Manual resistance from a therapist

40. Clinical Relevance
 Muscles used to descend stairs:
W=Weight of head, arms, trunk, and opposite
LE are the external forces acting producing a
flexion moment on the weight-bearing knee.
The quadriceps muscle apply an extension
moment to control the descent onto the lower step.

42. Interactions between joints and
the External Environment
 Closed kinematic chain
 Open kinematic chain

43. Clinical Relevance
Open-chain resisted knee flexion

44. Bilateral closed-chain resisted hip and
knee flexion/extension

45. General Changes with Disease, Injury,
Immobilization, Exercise and Overuse
1) Disease: In Rheumatoid arthritis-
Chronic inflammatory changes in synovial membranes
Synovium becomes congested and edematous
Proliferation of synovial cells, synovial hypertrophy
Resulting in joint instability
Joint deformities

46. 2)Injury:
-Joint support is decreased
-After injury, ligaments, tendons, and joint capsule subjected to
increased loading- excessively stretched-unable to provide
protection.
3) Immobilization:
-By a cast, braces, bedrest.
-Joint is immobilised for weeks- joint capsule shorten- contracture
will develop- normal range of joint motion difficult.
-Ligaments and tendons show decreased tensile strength and
stiffness.

47. 4) Exercise:
-Bone deposition is increased with weight-bearing exercises.
-Tendons respond by increasing collagen concentration, tensile
strength and stiffness.
5) Overuse:
-Repeated or sustained loads while tissue is still in a deformed
state.
-Also called as overuse injury or syndrome, repetitive strain
injury.
-Common in athelets, dancers, musicians, office workers.

48. Summary
- Classification and structure of human joints
- Properties of connective tissue
- Osteokinematics and arthrokinematics
- Factors influencing motion at a joint
- Changes occuring with disease, injury,
immobilization, exercise and overuse.

49. Questions
1) Classify synovial joints.
2) What is osteokinematics and
arthrokinematics?
3) Mention factors influencing joint
motion.
4) Explain Load deformation curve.

50. References
- Joint Structure and Function, Pamela K.
levangie, Cynthia C. Norkin, Fifth Edition,
Pg. no. 64-104.
- Kinesiology The Mechanics and Pathomechanics
of Human Movement, Carol A. Oatis, Second
Edition, Pg. no. 103-115.