The patellofemoral (knee cap) joint is made up of two bones: the patella (the knee cap) and the femur (the thigh bone). When the knee bends and straightens, the patella glides along a groove on the femur called the trochlea. Some people have differences in the way the knee cap and this bone fit together.
These variations can lead to problems with the patellofemoral joint. For example, when the patella sits too high in this groove, the patella is prone to dislocations. Altered alignment may also cause the joint surfaces to wear down which can cause pain. Problems in the patellofemoral joint can be divided into several groups:
- Chondromalacia Patellae
- Patellar Malalignment
- Patellar Subluxation/Dislocation
The undersurface of the patella is lined with cartilage. This cartilage provides a smooth surface for the patella to glide during knee movement. Chondromalacia is a condition that occurs when this cartilage breaks down. The pain may be along the sides of the patella or it may feel like it is deep inside the knee. Feelings of crunching or noise in the knee are an indication of chondromalacia.
Treatment of Chondromalacia Patellae
Treatment focuses on emphasizing full range of motion and strength. Rehabilitation will also address any muscle imbalances that may be contributing to the patellofemoral pain. In some cases, a knee arthroscopy may be necessary.
Patellar malalignment occurs when the patella does not contact the femur in an ideal position. The patella can sit too high or too far toward the outer (lateral) side of the knee. People who have patellofemoral pain often complain of pain after sitting for prolonged periods and with stair climbing. This malalignment can be congenital or the result of a traumatic injury.
Treatment of Patellar Malalignment
Problems with the alignment of the patella may require surgery. This can be determined on an individual basis after an evaluation by Dr. Shelbourne, Dr. Urch, or Dr. Benner. Rehabilitation focuses on restoring full, symmetric range of motion and strength.
Some people experience episodes where their patella will dislocate, or slip to the side. The injury is usually followed by swelling, stiffness, and pain. It is important to have a thorough knee examination to assess for any damage that may have occurred at the time of the dislocation.
Treatment of Patellar Subluxation/Dislocation
At first, treatment will focus on minimizing the swelling, walking normally without a limp, and restoring full range of motion. Once range of motion is full and the swelling has resolved, treatment will focus on strengthening. Sometimes surgery is also needed after a patellar dislocation. This can be determined on an individual basis after your evaluation.