Knee Cap or Patellar Pain
The Knee Cap or “Patella” and the structures that attach to it are the most common source of knee pain. It most commonly takes the form of “Chondromalacia Patellae” or “Patellar Tendinitis.” The knee cap is a late evolutionary adaptation that is not necessary for walking but allows increased mechanical advantage for vertical motion activities. It is injured gradually over time by climbing, descending and running on hard surfaces: activities for which nature did not intend our knees to be chronically used.
Diagnosis and Definition
Chondromalacia Patellae (CMP): This is inflammation, degeneration and in severe cases, erosion of the 3 millimeter thick layer of smooth cartilage that coats the patella on its inner surface. In its normal state this cartilage allows the joint to glide without friction. This problem is more common in people who have lateral patellar tilting or malalignment. This is a common hereditary condition in which the patella sits off center in its V-shaped groove which is called the “trochlea.” This malalignment can be seen on a “sunrise” knee x-ray. However most people with CMP do not have this problem. Many people with CMP will have “crackling” when they bend and straighten their knee. Pain is felt over the kneecap but can be “referred” to the inner or medial side of the knee. MRI is not necessary for diagnosis and often misses the problem. Special MRI techniques are necessary to detect how badly the cartilage is injured in severe cases.
Patellar Tendinitis (PT): This problem has often been called jumper’s knee and is more common in athletes who either jump or run on hard surfaces regularly. Patients do not have crackling of their knee. They do have tenderness at the lower border of patella when palpated. They also may have referred medial pain.
Treatment
Activity Modification: For both CMP and PT the most important treatment is the reduction of stress across the kneecap. This involves elimination of squatting and kneeling. Rather patients should sit on the ground or on a low stool or bucket when they need to perform low-to-the-ground activities such as gardening, scrubbing floors, playing with children or performing manual labor. Stair climbing should also be minimized. Any activity that causes pain should not be done. “Working through” the pain only results in more tissues destruction and cell death. Specific weight lifting to “strengthen” the quadriceps such as leg presses, leg extensions, squats, lunges, stepping etc. which in the past were held out as beneficial are actually quite likely to aggravate the problem and must be eliminated. The reduction or elimination of these activities allows the problem to gradually go away as healing occurs.
Physical Therapy: Hip exercises, flexibility training, hamstring strengthening and other strategies are beneficial in most patients. Again however isotonic quadriceps strengthening must be avoided. P.T. can greatly aggravate the problem if improperly performed.
Non-Steroidal Anti-inflammatory Drugs (NSAIDS) and Pain Medicines: These should be avoided for two reasons. First all NSAIDS, which includes, Motrin, ibuprofen, Naprosyn, aspirin, Vioxx, and many others inhibit collagen synthesis which is the backbone of cartilage and tendons – that is they slow down healing. Secondly, their pain relieving qualities, and this is true of Tylenol, Darvon, Vicodin etc., mask symptoms so that patients injure themselves more without knowing it. Patients taking NSAIDs or pain relievers of any kind typically present to a physician with a much more severe stage of the disease for this reason than patients who have not been medicated.
Time to Healing: With a proper activity modification and therapy program there is slow steady improvement but it is slow. Patients typically report a 15 to 20 percent reduction in symptoms the first months with total healing time average four to six months. Once healing has occurred it is important not to overload the patella again or the symptoms will occur.
The Role of Excessive Weight: Weight gain along with overuse is a principal cause of Patellar Pain. The structure of the knee is such that the compressive force on the patella is seven times body weight when descending stairs. Thus a 150 lb person exerts 1050 pounds of force on the kneecap. Even a 20 lb weight gain increases this force by 140 pounds. The kneecap is the most sensitive part of the knee to weight gain. Weight loss is always beneficial in overweight persons and is indispensable to recovery in many. Weight loss usually cannot be achieved by increasing exercise due to the knee disability. Decreasing daily caloric intake is always effective even without exercise and is the primary component of any weight loss program even in those without activity limitations. Consulting a nutrition professional is recommended.
Exercising: a stationery bike or elliptical trainer on low resistance is usually well tolerated. Heart rates as high as desired can be obtained by increasing rate or velocity. A physician should be consulted to identify ideal and safe levels. Free style swimming (but not the breast stroke frog kick) or walking in water is also usually well tolerated as is walking. However a strenuous aerobic workout cannot be achieved by simple walking. Running should be avoided until healing occurs and even after healing is a bad choice for an aerobic workout as it is traumatic to the patella. After healing, running in the context of recreational sports is usually well tolerated.
Surgery: Surgery is usually not necessary: we perform it in less than five per cent of patients with patellar pain. In the very few patients who fail the activity modification and therapy program surgical treatment is available and usually effective but still must be combined with the activity program after surgery. Surgical techniques include lateral release for patients with malalignment of the kneecap; and microfracture and autologous chondrocyte implantation to generate new cartilage.
Prognosis
While some activity compromises must usually be made, especially in persons with unusually patellar-stressful activities that involve repetitive climbing on ladders, the overwhelmingly majority of patients do quite well and are still able to satisfactorily perform work, daily living and recreational activities.
Case Histories:
Go to our case history for patient #6 to read about a patient who had patellofemoral surgery.
