Chondromalacia and Degenerative Arthritis

A patella that is well balanced, stable, and properly aligned in the femoral trochlea usually has normal articular cartilage surfaces.  Articular cartilage is the gliding surface that covers all of our joint surfaces.

If the patella is not well balanced, stable, or aligned, the articular surfaces commonly will deteriorate.  Early breakdown of the surfaces is called chondromalacia patella.  More significant surface breakdown or surface loss is called degenerative arthritis of the patellofemoral joint. Chondromalacia patella is not “Anterior Knee Pain” or “Patellofemoral Syndrome (PFS)” or any of the other terms used for patellar pain.  Chondromalacia patella is the breakdown of the patellar surface that can progress to degenerative arthritis.

Surfaces typically will breakdown from either overpressure or noncontact.  If the patella is tight to the lateral side of the trochlea, the lateral side of the patella is under pressure and the medial or inner side may not contact the trochlea at all. The noncontact lesions occur because the articular cartilage does not have the stimulation of gliding against opposing normal cartilage.  Either condition can cause breakdown of the patellar surface.  These patterns of surface breakdown can be easily seen by arthroscopy.

Other patterns of articular cartilage breakdown are seen as well without instability or major malalignment.  The patellar surface may be significantly damaged and irregular with an intact femoral trochlea.  The opposite may occur as well, an intact patella and severe breakdown of the femoral trochlea.

If patellar subluxation is present and the instability is significant, the surfaces of either the patella or femoral trochlea can be injured as the patella slides off the trochlea.  These lesions are articular fractures due to injury and are more commonly seen with acute patellar dislocation. However chronic patellar subluxation can also produce the same pattern of injury.

Lateral position of the patella without major patellar instability can also produce severe degenerative arthritis of the patellofemoral joint.  The lateral articular surfaces can slowly deteriorate and collapse due to overpressure.  The patella will actually move further lateral, partially off the femoral trochlea.  The end result of this progression will be complete surface loss of the lateral patella and femoral trochlea.  This progression can easily be seen by x-ray and will occur over time.  Patellofemoral Joint Replacement, a partial knee replacement, can be very effective treatment for this problem if the remainder of the knee is healthy.

Back to top