Introduction
The patella bipartita is a variation of the kneecap that has existed since birth, in which the patella does not consist of one bone part, but of two separate bone parts due to a disorder in the ossification (lat. bipartitus = divided into two parts). This plant variation usually has no disease value, is present in 2-3% of the population and occurs predominantly in boys or men.
In addition to the two-part patella, there may also be a three-part patella (Patella tripartita) or a patella consisting of more than three parts (Patella multipatita). The cartilaginous cover on the side facing the knee joint is not divided into two parts. The bone fragment separated from the rest of the knee joint is most often found in the upper-side area, but in some cases a kneecap separated into almost equal parts may be present.
Function of the kneecap
The patella is a triangular, flat bone disc that precedes the knee joint and plays a major role in its joint surfaces and joint function. It is embedded in the tendon of the large thigh muscle (Musculus quadriceps femoris) and functions as a kind of pulley or placeholder, optimizing the leverage of the thigh muscle, protecting the tendon of the muscle and the knee joint.
Symptoms
A kneecap divided in two or more parts usually causes no discomfort and is usually only discovered by chance during an X-ray examination of the knee. In a few cases, load-dependent symptoms may occur, similar to a disease of the cartilaginous surface of the kneecap (Chondropathia patellae): primarily it is pain during walking, especially when going downhill, as well as when sitting for long periods and squatting positions.
Diagnosis
Whether the patella consists of two or even more bone parts can be determined with the help of an X-ray image. Since it is not always possible to distinguish between a trauma-related, old, pseudoarthrotic patella fracture and a pseudoarthrosis, a bone scintigram may be helpful in unclear cases. In most cases, the patella bipartita is discovered as a chance finding in X-rays.
The patella is very clearly visible in X-rays, so that a patella bipartita can be diagnosed quickly. Often, however, the exact edges of the patella cannot be optimally examined due to overlapping of other bones, which often makes it difficult to distinguish it from a patella fracture. Therefore, magnetic resonance imaging (MRI) is often performed as an additional measure. This sectional imaging allows a more precise assessment of the tissue and the bony parts of the knee and a differentiation of the patella bipartita from a fracture.
