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How Strong Quadriceps Muscles Help with Anterior Knee

Anterior knee pain is a very common cause of knee pain in people across all ages. Some people may also know it as patello-femoral syndrome.

"Image illustrating the areas affected by w:en:Patellofemoral pain syndrome" by BodyParts3D/Anatomography under Licence CC BY 2.1
“Image illustrating the areas affected by w:en:Patellofemoral pain syndrome” by BodyParts3D/Anatomography under Licence CC BY 2.1

Anterior knee pain (or patello-femoral syndrome) is pain that is found in the front of the knee.

Anterior knee pain will commonly get worse when you use stairs.  Going downstairs is generally more painful than going upstairs, or going downhill is also generally more painful than going uphill.   This is because going downstairs or going downhill places a greater demand on your quadriceps muscles than going uphill or upstairs.  Anterior knee pain is also aggravated by any activity, movement or exercise that places strain on your quadriceps muscle and knee cap.  Why is this?

Firstly, you need to understand the parts of the body involved when you get anterior knee pain (or patello-femoral syndrome).  If you look at the illustration below, you will see that the knee cap is positioned above the thighbone (femur) and that there is a muscle that is attached to the knee cap via a tendon, that is called the quadriceps muscle.  The quadriceps muscle is actually made up of 4 muscle bellies (recently a 5th muscle belly has been discovered).

"Knee Anatomy"Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. with written author permission for use.
“Knee Anatomy”Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. with written author permission for use.

The action of your quadriceps muscle is to straighten the knee when the quadriceps muscle contracts.  Because the knee cap is attached to the quadriceps muscle, when you straighten and bend your knee, your knee cap moves up and down along the thigh bone in a groove.  This action is controlled by the quadriceps muscle.  In fact, your knee cap is there to shorten the lever of your quadriceps muscle and thus improve the contractile strength of your quadriceps muscle when it acts.  Thus they work together like hand and glove.

If you have weak quadriceps muscles, however, the knee cap is no longer well controlled in its movement up and down the groove in the thigh bone.  What happens is that when your quadriceps muscle contracts in this instance, your knee cap is pushed against the thigh bone and grinds the underside of your knee cap against your thigh bone, causing inflammation and your anterior knee pain/ patello-femoral syndrome.

What causes your quadriceps muscles to weaken and cause your knee cap to grind against your thigh bone creating anterior knee pain?  There are various scenarios.  A very common one occurs in children and teenagers, where a growth spurt has occurred and the bone is longer, but the quadriceps muscle and tendon haven’t caught up, causing a biomechanical imbalance resulting in anterior knee pain/patello-femoral syndrome.  Another scenario is when an injury to the knee has occurred that results in pain and swelling.  Any pain or swelling in the knee causes inhibition of your quadriceps muscle, which left untreated, can result in the development of secondary anterior knee pain/patello-femoral syndrome.  If you have had a knee injury, make certain that you have been to see your sports or OMT physiotherapist.  They are specially trained to help you resolve this problem quickly.

One of the factors that your sports or OMT physiotherapist will attend to is how to avoid anterior knee pain if you’ve had a growth spurt or knee injury or how to undo anterior knee pain caused by weak quadriceps muscles.

Since your weak quadriceps muscles are key to the problem of your anterior knee pain, knowing how to strengthen your quadriceps muscles in a pain free way, until the muscle is strong enough to pull your knee cap away from your thighbone while your knee bends and straightens during your activities, is pivotal in resolving the problem (read my post on strengthening your quadriceps muscles when you have anterior knee pain) and go see your sports or OMT physiotherapist for some treatment.

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