1. Mechanical Behavior of Tendon & Ligament
Physiotherapy
Semester – I

2. Mechanical Behavior of Tendons and Ligaments
Strong Viscoelastic structures
Sustain the high tensile forces
Sufficiently flexible to angulate around bone surfaces
Ligaments
Pliant and flexible to allow natural movements of the bones
Strong & inextensible to offer suitable resistance to applied forces

3. Stress-Strain Curve

4. Load-elongation Response
1: Primary or "Toe" region …
The tissue elongated easily with a small increase in load
2: Secondary or "Linear" region ….
The fibers straightened out & fibers’ stiffness increased
Greater force is required for elongation
Deformation of the tissue began
3: End of Secondary Region (P lin.)….
Progressive failure of the collagen fibers
Irreversible deformation
4: Maximum Load (Pmax) …..
Complete failure occurred rapidly and Lost its ability to support loads

5. Load-elongation Curves
Curve of tendon
Load-elongation
Curve of lig. flavum

6. Clinical Consideration
Ligament Failure …….
Progressive failure against increasing load
Stress – Strain Relationship
Microfailure & gross failure of ligament
Joint displaced several millimeter
Damage to the surrounding tissues as well
e.g. : ACL Injury in soccer as a result of an abnormal torque in rotation of the knee

7. Load-displacement curve of ACL Injury
Load imposed on the ACL during the ant. drawer test
Load placed on the ligament during physiological activity
Load imposed on the ligament from partial injury to complete rupture (Microfailure region)
Note: Why ACL Injury can lead to EARLY osteoarthritis?
Load-displacement curve

8. Ligament Injuries are classified clinically into three Categories
Grade-I Sprain …..
Mild pain, No joint instability, Micro-tear of few fibers
Grade-II Sprain …..
Severe pain, Some joint instability, Partial ligament rupture (Progressive failure of the collagen fibers)
50% decrease in Ligament strength (increase laxity with a definite end point)
joint stability is tested usually under anesthesia
Grade-III Sprain ….
Severe pain during trauma but less pain after injury
Gross instability (excessive joint laxity with no firm end point)
Complete ruptured but a few may still be intact

9. Management of Ligament Sprains
Grade I & II Sprain ….
First aid Management elecrophysical agents, joint mobilization & soft tissue massage muscle strengthening, proprioceptive training & Functional training
Grade III Sprain ….
First aid Management surgery ( repair or reconstruction) / protective bracing muscle strengthening, proprioceptive training & Functional training

10. Clinical Consideration of Tendon Injuries
Two additional factors become important in tendons ……
The amount of force produced by muscle contraction
The cross-sectional area of the tendon
Muscle contraction exerts a tensile stress on the tendon. rapid eccentric contraction of the muscle increases the stress
Tensile strength of a tendon α Cross-sectional area of the tendon
Why muscle ruptures are more common than are ruptures through a tendon?

11. Load Deformation Curve Of Achilles Tendon Rupture
First region … a normal physiological toe-loading response
Linear region …. high load is producing a higher deformation within the tendon structure
Overuse region …. Repetitive higher strains with insufficient time for the healing process

12. Tendonitis vs. Tendinopathy
Tendonitis …… inflammation of the tendon itself
Tendinopathy ….
The primary pathology is Collagen degeneration
Histological examination reveals separation of collagen bundles, increased hydrophilic ground substances, increased poor quality blood vessels ( neovascularization), and absent inflammatory cells
Common sites for tendinopathies are rotator cuff, common extensors origion of elbow, extensor carpi redialis brevis, patellar and Achilles tendons
Other sites add. Longus, biceps, tibialis post. And flex. Hallucis longus tendons.

13. Grading of Tendinopathy
Descriptive Grading of Tendinopathy ….
Mild Tendinopathy….
Pain after activity only / no pain during activity
Moderate Tendinopathy ….
Pain with sporting activity but not with ADL
Severe Tendinopathy ….
Pain during ADL
Tendon-specific scoring system…..
The VISA Score e.g. patellar tendinopathy

14. Tendinopathy Characteristic features …..
Pain some time after exercise or, more frequently, the following morning when the athlete rises
Can ‘run through’ the pain or pain disappears in warming up & return after exercise when cooling down
On Examination: Local tenderness, thickening, swelling, crepitus
Management ….
Eccentric loading exercises vs. concentric exercise
Surgery is indicated on clinical basis ( stripping of paratenon, release of adhesions, removal of degenerative tissues, repair of a partial tear or excision of a torn flap)

15. Age- related changes of collagen
Collagen cross-links vs. Aging:
The greater the no. & quality of cross-links, the more tensile strength of collagen (Viidik, Danielsen, & Oxlund, 1982)
Collagen fibril diameter vs. Aging:
Fibril diameter α the tensile strength of ligament and tendons
Fibril diameter in adults (20-60 years) & in elderly (>60 years) decreases remarkably (Strocchi et al., 1996)
Water content & concentration of collagen vs. Aging:
The water content & collagen conc. decreases significantly in ligament as age progresses after maturation (Amiel, 1991). So, tensile strength & stiffness of the ligament & tendon decreases

16. Mobility vs. Mechanical behavior of Ligament & Tendon
Functional adaptation of ligament & tendon in response to the mechanical demands placed on them
The ligaments are more stronger & stiffer when subjected to increasing stress and more weaker & lesser stiffer when subjected to decreasing stress (Noyes et al., 1977a)
Physical training increases the tensile strength of tendons and ligament-bone interface (Woo et al., 1981).
Research study of medial collateral ligament strength:
The ligaments of the exercised dogs for 6 weeks were stronger & stiffer than those of the control dogs & the collagen fiber bundles had larger diameters (Tipton and coworkers, 1970)

17. Diabetes Mellitus Diabetes mellitus VS. Musculoskeletal disorders
Diabetics vs. Nondiabetics ….
Higher rates of tendon contracture (29 vs. 9%)
Tenosynovitis (59 vs. 7%)
Joint stiffness (40 vs. 9%)
Capsulitis (16 vs. 1%)
Also causes osteoporosis (Carvallo et al., 1991; Lancaster et al., 1994)
The tissue elastic properties did not differ between the diabetic and the control group. The viscous component of the tissue response, however, was increased in the hyperglycemic group. Insulin therapy seems to lessen such alterations (Duquette, 1996)

18. Nonsteroidal Anti-inflammatory Drugs
NSAIDs (aspirin, acetaminophen and indomethacin) are frequently used in painful conditions of the musculoskeletal system
also widely used in the treatment of soft tissue injuries such as inflammatory disorders and partial ruptures of tendons and ligaments
Vogel (1977) found that treatment with indomethacin resulted in increased tensile strength in rat tail tendons. An increase in the proportion of insoluble collagen and in the total collagen content also was observed
Ohkawa (1982) found increased tensile strength in the periodontium of rats after indomethacin treatment
Carlstedt and associates (1986a, 1986b) found that indomethacin treatment increased the tensile strength in developing and healing plantaris longus tendons in the rabbit and noted that the mechanism for this increase was probably an increased cross-linkage of collagen molecules