Patella-Femoral Stress Syndrome

By Chad M. Thompson, M.S.P.T, O.C.S.

Knee pain can result from injury to numerous tissues around the knee joint. This article addresses a unique condition common among athletes of every skill level and age - pain under and to the side of the patella (knee cap). Patella-femoral dysfunction can result in a patella-femoral stress syndrome. This condition occurs when structures on the lateral side of the knee become taught, losing flexibility or when muscles inside the upper leg weaken, failing to control femoral rotation and patella glide.

Normal mechanics between patella and the femur (thigh bone) can be observed from knee flexion (bending the knee) to extension (straightening the knee). If we use the right knee as an example the kneecap will "glide" toward the left shoulder starting from a bent knee to a straightened position. The muscle primarily responsible for this motion is the vastus medialis oblique (VMO), a portion of the quadriceps.

The VMO muscle is responsible for tracking the patella along the natural groove in the femur. The adductor group controls rotation of the femur, contributing to overall stability of the knee. Muscles attaching at the lateral side of the knee balance the function of the VMO and adductor group. These muscles are tensor fascia late, gluteus minimus, piriformis and hamstrings.

When this normal balanced relationship is disturbed by injury, loss of flexibility or anatomical variance a lateral pain syndrome can result. The individual will complain of pain under and to the outside of the kneecap. They will be sore to touch on the lateral end of the femur. This occurs because the patella is not tracking correctly in the groove. When the knee bends, the kneecap rides over the outside of the femur irritating the underlying tissue. This will cause the rubbing or grinding complaint verbalized by our clients or athletes.

Treatment involves stretching the lateral compartment of the affected knee. Specifically we stretch the tensor fascia latae as it has a tethering band running over and attaching on the inside of the kneecap. We also stretch the piriformis and hamstring musculature to achieve normal flexibility between the hip and knee.

Strengthening the VMO and inside muscles of the knee help our patients control rotation and restore normal glide to the kneecap. When rehabilitation is complete, stress on the lateral kneecap and femur is relieved by restoring normal mechanics. Literally we want the patella "back in the groove."

Chad M. Thompson, M.S.P.T., O.C.S., is the director, KORT-Georgetown Physical Therapy in Georgetown, KY. Chad can be reached at cthompson@kort.com.