1. The Knee Joint

2. The Knee Joint • Hinge joint? • Double-condyloid joint • Flexion and Extension • Internal and External Rotation • The locking of the knee into full extension is often referred to as the “screw home” movement • Tibia externally rotates 10 degrees • Biceps femoris • Initial flexion of the knee, the knee “unlocks” • Tibia internally rotates • Popliteus, semitendonosus, semimembranosus

3. Two-Joint Muscles • Uniarticulate • A muscle that crosses one joint • Biarticulate • A muscle that crosses two joints

4. Two-Joint Muscles • Two-joint muscles are most effective when either the origin or insertion is stabilized. • Why? • Explain the benefit of leaning backwards while kicking a ball.

5. Two-Joint Muscles • A muscle's ability to contract dependent upon its length, or degree of contraction. • A muscle can contract more forcefully when it is slightly stretched. • Muscle generates maximal concentric tension at a length 1.2 times its resting length.

6. Two-Joint Muscles • During knee FLEXION, what muscle group is being stretched? • What affect will this have on that muscle groups ability to contract? • During knee EXTENSION, what muscle group is being stretched? • What affect will this have on that muscle groups ability to contract? • How do these relationships help during running?

7. Quadriceps • The quadriceps function as a decelerator when it is necessary to decrease speed for changing direction or running downhill or to prevent falling when landing. • What type of contraction does deceleration require? • What ultimate affect does this type of contraction have on muscle strength? • What ultimate affect does this type of contraction have on muscle soreness?

8. Quadriceps • What is a typical test that measures the strength of the quadriceps muscles? • Strong quadriceps muscles are essential for maintenance of patellofemoral stability • The vastus medialis muscle is not emphasized until the last 10-20 degrees of knee extension

9. Acute Knee Injuries

10. Causes of ACL Injuries • Cutting (rotation) • Hyperextension • Straight knee landing • When the knee is extended, the ACL is at it’s maximal length putting it at an increased risk of tearing

11. Unhappy Triad • ACL • Medial collateral ligament • Medial meniscus

12. Lachman Test and Anterior Drawer Test • Normal knees have 2-4 mm of anterior translation and a solid end point • ACL injury will have increased translation and a soft end point

13. Chronic Injuries • Patellar Tendonitis • Patellofemoral Pain Syndrome • Subluxation of Patella • Chondromalacia • Osgood-Schlatters Disease • IT Band Syndrome

14. Patellar Tendonitist

15. Patellar Tendonitist • Due to high deceleration or eccentric forces of the quadriceps at the knee during landing • As you land the hamstrings cause your knee to flex to absorb the shock of impact • In order to control or decelerate the flexion produced by the hamstrings, the quadriceps muscles contract eccentricly • Eccentric contractions occur as the muscle is being lengthened or stretch • Eccentric contractions produces high amounts of force, and therefore stress to the patellar tendon

16. Patellar Tendonitist • Prevention: strong quadriceps muscles Lunges Squats

17. More Quadriceps Exercises Leg Extension Leg Press

18. More Quadriceps Exercises Plyometric or Jump Training Uphill Running

19. Hamstring Exercises

20. Hamstring Exercises

21. Chondromalacia • This is a Latin term meaning “bad cartilage” or breakdown or softening of the articular cartilage of the patella • The cartilage surface on the underside of the patella becomes soft. Part of the cartilage can become stringy and flake off at times. Part of the surface may become roughened. • Causes (FYI) • Training errors • Increasing intensity too soon • Weak vastus medialis muscle • Large Q angle • Greater than 25 for women and 20 for men • Pronation of the foot causing the tibia to medial rotate • Gender - more common in women • Poor footwear and/or surface

22. Patellofemoral Stability

23. Osgood- Schlatter Disease • Overuse, not a diesease. • Inflammation to the patellar tendon at the tibial tuberoscity • Most common in adolescents (8-13 year olds girls and 10-15 year old boys); age of rapid bone growth

24. Osgood- Schlatter Disease • Anterior pain about 2-3 inches below the patella • Avulsion fracture

25. IT Band Syndrome • Excess duration or time exercising • Hip abductor weakness • Tight hip abductors and/or IT band