Patella baja is a condition where the kneecap is positioned in an abnormally low position. It is also known as patella infera.

 

The abnormal position causes more pressure onto the edge of the kneecap, which may lead to considerable pain, as the kneecap impinges against the tibia when the knee bends - and arthritic changes can occur at the back of this bone. Range of motion may be decreased in both flexion and extension.

normal knee, before onset of arthrofibrosis sites of arthrofibrosis in the knee Advanced arthrofibrosis of the knee
Side view of section through a normal knee, where there are no adhesions locking up movement. Adhesions developing in the suprapatellar pouch, posterior capsule and anterior interval may create flexion loss, extension loss or both. Matured scar tissue has contracted, closing the important spaces that normally allow movement, and pulling the kneecap right down.

 

Causes of patella baja

Patella baja may be a consequence of total knee replacement or high tibial osteotomy due to inflammation and scarring within the front of the knee joint and behind the patellar tendon -  in the region known as the anterior interval. It may also be seen in any condition where 'arthrofibrosis' has been triggered in the anterior interval, such as following joint infection or a long period of knee immobilisation.

 

Monitoring arthrofibrosis by the height of the patella

Because the scarring of arthrofibrosis of the anterior interval tugs the patella down, serial X-rays of kneecap position can help the surgeon to evaluate deterioration in the arthrofibrotic condition and the need for surgical intervention such as lysis of adhesions and anterior interval release.

 

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