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Quadriceps Atrophy; what causes it

Asian physiotherapists are checking patients' knees.
Author- judith Nassaazi

The quadriceps muscle is such a powerhouse in the lower extremities.  These are the muscles located on the front of (anterior aspect) the thigh. Quadriceps atrophy refers to the shrinkage in size of the quadriceps muscle.

The quadriceps are made up of 4 different muscles which are the rectus femoris, vastus lateralis, vastus intermedius and vastus medialis which merge to form one strong tendon known as the Quadriceps tendon.  

Quadriceps are part of a complex mechanism that allows your knee to straighten. However, many injuries contribute to quadriceps atrophy.

This article will summarise the most common causes of quadriceps atrophy.

Quadriceps muscles in tension
Quadriceps muscles in tension

causes of quadriceps wasting

1. Anterior cruciate ligament injury (ACL injury).

The anterior cruciate ligament also termed the ACL in short is a tough band in the knee connecting the femur to the tibia bones; that controls the forward movement of the knee joint.

Quadriceps atrophy begins once this ligament is injured and has been found to be present even close to 6 months following its reconstruction.

The exact cause for this is not known but it’s central and peripheral mechanisms are implicated.


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2. Patellofemoral pathology

Aside from the joint between the thigh bone (femur) and the shin bone, there also exists a joint between the Patella bone or the knee cap, with the femur. This joint is called the patellofemoral joint

Therefore, patellofemoral pathology refers to problems that affect the joint formed between the patella and the femur.

 Patellofemoral pathologies present with knee pain. This often leads to an inhibitory signal and reduced activation of the quadriceps.

3. Fracture of the femur

Fractures of the femur lead to immobilization of the limb. This immobilization is associated with a reduction in muscle size due to disuse.

4. Osteoarthritis of the knee.

Due to pain in the knee associated with osteoarthritis, there could be an inhibitory reflex that reduces the limb’s function.

Shrinking of these muscles could follow many causes which may include; in some cases, there are episodes of immobilization to alleviate pain.

There is also a tendency to brace the affected joint to alleviate pain and all this can lead to atrophy of the muscles from reduced use.

Note that these causes will lead to localized atrophy of the affected thigh and not the other. If experiencing generalized atrophy of muscles with weight loss, that could be a different condition altogether and you need to see your physician.

In conclusion, there are many causes of quadriceps atrophy but the above are the most common cause of isolated shrinkage of the quadriceps. Talk to your doctor to get a solution.

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