Knee Joint Stabilisation

The stability of the knee joint is dependent upon static and dynamic factors.  The static stabiliser includes passive structures such as the knee joint capsule and the various ligaments and other associated structures such as the menisci, the coronary ligaments, the menisco-patella and patello-femoral ligaments.  The ligaments which all act as static stabilisers include the medial collateral ligament, the lateral collateral ligament, the ACL, PCL, the oblique popliteal and arcuate ligaments.  The ilio-tibial band is also considered a static stabiliser in spite of its muscular connections. 

The bony geometry also contributes to the static stability of the knee.  The contribution is variable but can be made worse by certain anatomic variants such as a flat lateral femoral trochlea which will predispose to lateral instability of the patella.

The dynamic stabilisers of the knee are all the muscles and their aponeuroses including:
1. quadriceps femoris and extensor retinaculum, 2. pes anserinus, 3. popliteus, 4. biceps femoris, 5. semi-membranosis.  The structures on the medial, antero-medial and postero-medial side of the knee are medial compartment structures and stabilisers and structures on the respective lateral side are lateral compartment stabilisers.

The contribution that both muscles and ligaments make to stability is dependent on joint position of the knee and the surrounding joints, the magnitude and direction of the force and the availability of reinforcing structures to resist forces if the primary restraints become incompetent.