Patella (Knee cap)

Knee specialists approach to osteoarthritis of the knee ©Viewmedica

Knee pain may be due to Patella Tacking Disorder (PTD). The patella syndrome may be caused by a problem with the bones, muscles or ligaments which support the patella (knee cap), helping it to remain in the correct place.

What is the function of the kneecap?

The kneecap or patella is a bone enveloped by the great extensor tendon of the thigh muscles. Its posterior surface slides up and down within a groove on the end of the thigh bone. Due to its congruent triangular shape, the kneecap normally fits perfectly into the groove (trochlea). The muscle contraction is transferred directly to the lower leg and extends and straightens the knee.

Patella dislocation with loose articular body (image on left). © joint-surgeon.com

If there are no significant malaligments of the knee cap (patella deformity) the knee cap can be stabilized by treating the ligaments which hold the knee cap in place.

The inner ligaments, particularly the medial patellofemoral ligament (MPFL), have key role in stabilizing the patella. In some cases, only a slight tightening of the medial patellofemoral ligament (MPFL) is all that is required to stabilize the patella.

For many decades Lateral Release was the most popular surgical treatment for chronic patella instability.

The severing of the outer retaining ligaments of the patella (lateral release or cleavage of the lateral retinaculum) was, for a long time, considered an appropriate solution to the instability of the patella. It was believed that by cutting through the outer bands of the ligament, the patella would return to its natural position, thus reducing the tendency to dislocate.

The basic requirements for the successful treatment of kneecap dislocation are a complete case history and a thorough physical examination.

Long-term effects of patella dislocation

Each episode of patella dislocation can cause irreparable damage to the cartilage surface of the patella. In many cases, the dislocation results in osteochondral shear fractures. Loose bone or cartilage fragments may lock the joint, which may lead to further cartilage damage at other parts of the joint. There is also the risk of tearing the intra-articular ligaments of the articular capsule.

What are the long-term prospects following treatment for knee cap dislocation?

The sooner the treatment is initiated, the better the long term outcome. However, in most cases treatment is started too late. The majority of patients, particularly younger ones, tend to consult their doctor only when the dislocation has become a recurrent problem.

If treated early, success rates for long term stability in the knee joint without any discomfort, would be over 80 percent. When diagnosis and subsequent therapy are delayed, the likelihood of a successful long term outcome as described above, drops to below 20 percent and the development of arthritis in the knee joint (femoropatellar joint) is common. Chondropathies and severe cartilage damage are also often associated with this condition when it is left untreated.