Tendon and Ligament

Roles of Ligaments and Joint Capsules u Assist in Stabilization of Joint u Restrict Movement u Prevent Excessive Motion

Roles of Tendons u Attach muscle to bone u Transmit tensile loads u Position of muscle relative to joint

Mechanical Behavior of Tendons and Ligaments u Both are viscoelastic tissues u Visco - a small amount of load results in quite a bit of deformation (relative) u Elastic - refers to Elastic Region u Importance of viscoelastic qualities?

Properties of Tendon u can sustain high tensile loads u flexible to allow changes in direction of muscle pull

Properties of Ligament u guides movement u resists applied force

Mechanical Properties of Tendon and Ligament u Strength u Stiffness

Damage to Tendon and Ligament u When load is great enough to cause injury, damage is dependent on: u rate and u amount of load

Load-Deformation Curve for Tendon and Ligament u (0,0) - A: Toe Region u A - B: Elastic Region u B: Yield Point u B - C: Plastic Region u C: Ultimate Failure Point

Comparison of Bone to Tendon and Ligament u Identify similarities and differences between these tissue types.

Mechanical Properties of Tendon and Ligament u Strength u Stiffness

Injury Mechanisms u Injury occurs when tissue is loaded beyond its physiological range. u Microfailure occurs before the yield point is reached.

Injury Mechanisms cont. u When yield point is exceeded, the ligament begins to undergo gross failure. u Results in abnormal joint displacement u Displacement results in...

3 Clinical Categories of Ligament Injury u Negligible Clinical Symptoms (Grade 1) u no joint instability can be detected clinically u Severe Pain (Grade 2) u joint instability can be detected clinically u strength and stiffness decreases by 50% u instability can be masked by muscle involvement

3 Clinical Categories of Ligament Injury cont. u Severe Pain (Grade 3) u severe pain experienced during the injury with less pain after the injury u joint is completely unstable u most collagen fibers have ruptured

Noyes Study (1977) u Rhesus monkeys u 8 wks immobilization u returned to mobilization u at 12 mo. mechanical properties were comparable to non-immobilized ligaments. u Drumroll?

Additional Factors Important in Tendon Injury u Amount of force produced by muscle u Stress comparison between tendon and muscle u Loading Rates

Factors Affecting Biomechanical Properties of Tendon and Ligament u Aging u Pregnancy u Mobilization vs. Immobilization u NSAIDs

Osteoarthritis u Researchers suggest that a deficiency in mechanisms that minimize peak forces may cause osteoarthritis.