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
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 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
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
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