Knee Joint Muscles

The knee joint is affected by several muscles, including the quad muscles, hamstrings and Gastrocnemius. The muscles on this page are those that surround the front of the knee cap and affect the functioning of the patellofemoral joint. Also included is the popliteus, which unlike other mucles around the knee, functions only on the knee.

Click the pictures below for more information on muscle attachments, actions and nerve supplies.

Vastus lateralis

The most lateral of the quadricep muscles.


Vastus intermedius

A deep, central quad muscle.


Vastus medialis

The most medial of the quadricep muscles.



A small muscle at the back of the knee joint.


The four quadricep muscles act to extend (straighten) the knee joint. They are also important in the movement of the knee cap. All four quad muscles converge at the top of the patella into one tendon - the patella tendon - which attaches to the top of the shin bone. The patella is a sesamoid bone which means it is encased within the tendon and slides up and down in it's grove at the front of the knee. Commonly, the vastus lateral muscle is stronger and tighter than the vastus medialis (specifically the VMO portion). This can result in mal-tracking of the knee cap, as occurs in patellofemoral pain syndrome.