Kneecap Dislocations

Introduction/ What is?

Kneecap dislocations are fairly common injuries, more often seen in children or young adults. They are usually the result of sports injuries.

What are the symptoms?

The common symptoms of collateral ligament tears are:

  1. Popping sound/ feeling during the injury
  2. Significant pain at the front of the knee
  3. In some patients, the kneecap dislocates and pops back in place quickly. In these cases, they are still able to stand and limp after the injury. In other cases, the kneecap dislocates and stays displaced. Patients will experience severe pain in the knee, are unable to straighten their knees themselves and are unable to stand or move the knee.
Anatomy/ Pathology

The kneecap (patella) is a small bone sitting at the front of the knee joint (comprising the thigh bone and shin bone). It should stay at the front of the knee joint throughout the entire range of movement of the knee. It is kept in place by a combination of neatly fitting in a groove in the thigh bone at the front of the knee, as well as a thin, flat ligament connecting the inner edge of the kneecap to part of the thigh bone. This ligament is known as the medial patella-femoral ligament (MPFL).

If a twisting or direct impact of sufficient force is applied to the knee, the kneecap can get dislocated to the lateral side of the knee with resultant tear of the MPFL.

What caused it?

Sports injuries where the foot is firmly planted on the ground whilst the shin bone is twisted outwards with respect to the thigh bone, is the most common way kneecap dislocations occur. Alternatively, high impact to the inner side of the kneecap can also cause it to dislocate.    

Can it heal?

Yes the collateral ligaments can heal. However complete recover can take many months. Often in excess of half a year. Once they are healed, sporting ability is usually not significantly affected.

What tests can be done to diagnose this?

In an acute kneecap dislocation, the appearance of the knee with the kneecap awkwardly displaced to the side of the knee makes diagnosis straightforward in most instances. If need be, an x-ray will clearly demonstrate the injury. 

In cases where the kneecap had quickly popped back in place, clinical diagnosis is not so straightforward. In those cases, an MRI scan is the most reliable way to diagnose the problem.

What treatment options are there?

If the kneecap is acutely dislocated, it needs to be put back in place as soon as possible. This is usually easily done once pain-killers have been administered and the knee can be straightened. This will usually allow the kneecap to pop back in place by itself.

If it were the first time a kneecap dislocation had occurred, there may be a role of conservative treatment in the form of RICE (rest, ice, compression, elevation) and physiotherapy. 

There is a significant risk however, that the kneecap dislocation may occur again as the MPFL is often torn and its function is impaired. 

In patients who do not want to, or cannot afford to risk another kneecap dislocation, a relatively simple surgical procedure where the MPFL is either repaired (in acute cases) or reconstructed (in recurrent cases), can be performed.