1. Ligaments and Tendons

2. Ligaments zAugment the mechanical stability of joints zGuide joint motion zPrevent excessive motion

3. Tendons zAttach muscle to bone zTransmit tensile loads from muscle to bone

4. Composition z Dense connective tissue (parallel-fibers of collagen) - Sparsely vascularized z Cellular (fibroblasts) – 20 % z Extracellular (80%) - 70% H 2 O - 30% solids –collagen, ground substance, elastin

5. Composition z Collagen - ligaments - 75% of solids - tendons – 75%+ of solids

6. Ligament/Tendon Schematic

8. Ligament versus Tendon

9. Tendon - Structure and Function z sustain high tensile forces z flexible

10. Ligament - Structure and Function z pliant and flexible z strong and inextensible/inelastic

11. Injury is affected by: z Rate of impact z Amount of load

12. Tendon Deformation Load 1 2 3 4

13. ACL Injury

14. Joint Displacement Load Complete Failure Clinical Test Microfailure Physiological Loading Injury

15. Ligamentum Flavum Deformation Load

16. Factors affecting Mechanical Properties zMaturation -  20  # & quality of cross-links    tensile strength and  collagen fiber diameter (hypertrophy)

17. Factors affecting Mechanical Properties zAging – collagen content    stiffness, strength & ability to withstand deformation zPregnancy and postpartum – tensile strength & stiffness in tendons 

18. Factors affecting Mechanical Properties zPhysical Training -  tendon tensile strength and ligament- bone interface strength - ligaments become stronger and stiffer, collagen fibers increase in diameter

19. Factors affecting Mechanical Properties zImmobilization -  tensile strength of ligaments, more elongation, less stiff -  in cross-links -After 8 weeks of immobilization  12 months to recover strength & stiffness

20. Effects of Immobilization

22. WeeksMonths Time 0 Structural/mechanical properties (Experimental/Control x 100) 0 50 100 Control Exercise Immobility Recovery (ligament substance) Recovery (insertion site)

23. Factors affecting Mechanical Properties zNSAIDS -  tensile strength possibly due to  cross-linkage zLocal Cortisone - alters collagen organization in tendon - random versus parallel