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OA and the Quadriceps

September 14, 2012

Quadriceps Musculature

The quadriceps is a muscle group in the front of the thigh.  It is composed of the vastus lateralis, vastus intermedius, vastus medialis, and the rectus femoris muscles.  The vastii connect the thigh bone to the knee-cap and shin bone.  The rectus femoris stretches from the pelvis to the shin.  The primary function of the quadriceps is to straighten the knee, but because of the rectus femoris’s origin on the pelvis, it can also bend the leg at the hip.  The quadriceps are often used with the foot on the ground but can fire when the leg kicks.  When the foot is on the ground the quadriceps will contract to control knee bending and leg straitening.  This means that the quadriceps are important in activities like climbing and descending stairs, and sitting down and getting up from a chair.

Because the quadriceps muscles cross the knee, when they contract, they increase forces on the joint.  This extra pressure can increase friction, which can put stress on cartilage.  This means that using the quadriceps can increase pain for individuals with osteoarthritis of the knee.  Tension in or spastic firing of the quadriceps can put prolonged stress on the inflamed joint.  Individuals with weak quadriceps hyper-extend their knees when they walk.  This promotes stability but is damaging to knee ligaments and the hamstring muscles.  This also dramatically increases the stress on the cartilage and bone in the front of the knee.

Excessive tension in the quadriceps may be treated with slow stretching.  Spasticity and quadriceps weakness have more rigorous treatments, often including bracing.  For quadriceps weakness, bracing is often implemented to support the knee and prevent hyper-extension.  More sophisticated braces provide that support only when the leg is supporting body weight, while other braces may lock the knee full-time.  Quadriceps strengthening exercises are often recommended for individuals with osteoarthritis of the knee in order to avoid the pathological gait associated with quadriceps weakness.



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