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
Two-Joint Muscles • Uniarticulate • A muscle that crosses one joint • Biarticulate • A muscle that crosses two joints
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.
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.
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?
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?
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
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
Unhappy Triad • ACL • Medial collateral ligament • Medial meniscus
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
Chronic Injuries • Patellar Tendonitis • Patellofemoral Pain Syndrome • Subluxation of Patella • Chondromalacia • Osgood-Schlatters Disease • IT Band Syndrome
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
Patellar Tendonitist • Prevention: strong quadriceps muscles Lunges Squats
More Quadriceps Exercises Leg Extension Leg Press
More Quadriceps Exercises Plyometric or Jump Training Uphill Running
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
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
Osgood- Schlatter Disease • Anterior pain about 2-3 inches below the patella • Avulsion fracture
IT Band Syndrome • Excess duration or time exercising • Hip abductor weakness • Tight hip abductors and/or IT band