Sheila M. Algan, MD and Mark Anderson, PT, PhD, ATC
Sep. 15, 2010
Pain at the front of the knee (patellofemoral area) can be caused by many problems, including patellar tendinitis, Osgood Schlatter disorder, patella (knee cap) compression syndrome, knee cap instability, knee cap “tracking” problems and osteoarthritis. These problems are often not associated with a particular injury event and may have gradual onset. Early on, symptoms may resolve with a period of rest, ice and short term use of anti-inflammatory medication. Pain originating in the patellofemoral area of the knee generally occurs as a result of weakness in muscles that cross the knee and about the trunk and hip, which are responsible for controlling the position of the knee cap and maintaining the body over the feet during athletic activity. When these muscle groups do not function properly, forces about the knee joint will exceed the tissue’s threshold, resulting in pain and/or injury.
Patellar tendinitis occurs as a result of degeneration of the upper area of the tendon attaching the kneecap to the lower leg bone (tibia). A portion of the tendon will undergo breakdown of the fiber structure, usually just below the kneecap. This is often associated with some degree of inflammation and ingrowth of small blood vessels. Athletes with this condition experience pain in the tendon just below the kneecap which begins shortly after the onset of activity, particularly running, jumping and abrupt stopping/ change of direction.
Patellar tendinitis responds to therapeutic exercise to address tight hamstring muscles (back of thigh), tight quadriceps (front of thigh) muscles, and strengthening exercises. Early use of therapeutic modalities, such as phonoophoresis (deep heating ultrasound with anti-inflammatory medication) , may improve blood flow and decrease what pain and inflammation exists. Steroid injections in this area are not recommended due to the risk of the tendon tearing. Spontaneous rupture of diseased tendon is uncommon, but can occur with longstanding tendinitis. Some athletes will have pain relief with the use of a strap placed about the leg just below the area of soreness. Surgery is rarely required to remove the damaged area of the tendon.
Patellar compression syndrome is a condition in which the kneecap rests in a tilted position toward the lateral (outside) aspect of the knee, due to tight tissues at the outer aspect of the knee (lateral retinaculum) or weakness of muscle (vastus medialis obliquus or VMO) that support the medial (inside) of the kneecap. This results in pain beneath the lateral (outer) aspect of the kneecap.
Patellar maltracking is a related condition in which the kneecap “tracks” poorly in its groove on the thigh bone (femur), due to muscle strength and flexibility imbalances. It can be associated with abnormality to the shape of the femur where the knee cap normally sits (trochlea), to alignment between the hip, knee and lower leg (Q angle), to the shape of the patella, and to position of the foot such as abnormal flattening of the arch or pronation. Most commonly, it is associated with strength deficits of the trunk (“core”) and hips/pelvis. Athletes experience pain at the front of the knee with running, jumping, and stairs, and with prolonged sitting.
Both conditions most often respond well to physical therapy for therapeutic exercise including stretching of the iliotibial band (thick tendinous band at the outside of the thigh), hamstring muscles, and strengthening of the outer hip muscles, and patellar stabilizing muscles such as the VMO. The outer hip muscles include large muscles such as gluteus medius, but also smaller muscles such as piriformis. These muscles are responsible for moving the leg away from the body, for rotating the hip to the outside, and most importantly, supporting the pelvis while weight-bearing. Strengthening exercises may be accompanied by a taping technique intended to assist in promoting correct muscle firing patterns. For athletes with mechanical problems such as abnormal pronation, orthotics (shoe inserts) may be prescribed to correct the foot position. Some athletes may experience pain relief with the use of a brace which assists the kneecap in the way it “tracks”. Occasionally, surgery will be needed to release the tissue at the outer aspect of the kneecap (lateral release) for lateral patellar compression. Surgery for maltracking patella is often more complex, requiring soft tissue and/or bony procedures to improve knee cap tracking if symptoms do not resolve with nonsurgical measures.
The surface cartilage on the back of the kneecap is the thickest in the body, and withstands great forces. Arthritis in the knee can involve the cartilage on the surface of the kneecap where it makes contact with the thigh bone (trochlea), known as patellofemoral arthritis. Arthritis begins as a softening of the surface cartilage (chondromalacia) which can progress on, to breakdown of the surface and ultimately complete loss of the smooth surface, resulting in exposed bone. This is a progressively painful condition which can result in loss of function over time. It does respond to the therapeutic exercises previously discussed, particularly if addressed early. It may also respond to corticosteroid injection or joint lubricant injection in more advanced disease. Surgical procedures are available to treat local areas of loss of cartilage to this area of the knee; however, such procedures are generally not used when large areas of surface cartilage are lost. Research is being done on partial knee replacements for the patellofemoral joint, but long term results are not yet available.
Osgood Schlatter Disorder and patellar instability will be discussed in another segment.