The Knee Joint

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

Acute Knee Injuries

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

1. ACL

2. Medial collateral ligament

3. 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

1. Patellar Tendonitis2. Patellofemoral Pain Syndrome 3. Subluxation of Patella4. Chondromalacia5. Osgood-Schlatters Disease6. IT Band Syndrome

Patellar Tendonitist

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

Squats Lunges

More Quadriceps Exercises

Leg Extension

Leg Press

More Quadriceps Exercises

Plyometric or Jump Training Uphill Running

Hamstring Exercises

Hamstring Exercises

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)1. Training errors

Increasing intensity too soon

2. Weak vastus medialis muscle3. Large Q angle

Greater than 25 for women and 20 for men

4. Pronation of the foot causing the tibia to medial rotate5. Gender - more common in women6. Poor footwear and/or surface

Patellofemoral Stability

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