The Knee Joint

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The Knee Joint
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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

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Two-Joint Muscles

• Uniarticulate
• A muscle that crosses one joint
• Biarticulate
• A muscle that crosses two joints

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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.

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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.

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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?

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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?

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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

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Acute Knee Injuries
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Causes of ACL Injuries

• Cutting (rotation)
• Hyperextension
• Straight knee landing
• When the knee is extended, the ACL is at its
  maximal length putting it at an increased risk of
  tearing

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Unhappy Triad

1. ACL
2. Medial collateral ligament
3. Medial meniscus

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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

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Chronic Injuries

1. Patellar Tendonitis
2. Patellofemoral Pain Syndrome
3. Subluxation of Patella
4. Chondromalacia
5. Osgood-Schlatters Disease
6. IT Band Syndrome

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Patellar Tendonitist
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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

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Patellar Tendonitist

• Prevention strong quadriceps muscles

Lunges
Squats
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More Quadriceps Exercises
Leg Extension Leg Press
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More Quadriceps Exercises
Plyometric or Jump Training Uphill Running
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Hamstring Exercises
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Hamstring Exercises
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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

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Patellofemoral Stability
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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

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Osgood- Schlatter Disease

• Anterior pain about 2-3 inches below the patella
• Avulsion fracture

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IT Band Syndrome

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