How to "knock out" knee painKnee pain is one of the most common complaints seen in an arthritis physician’s office. The knee consists of the femur (upper leg bone), tibia (larger of the two lower leg bones), and the patella (the knee cap). There are three compartments in the knee: the medial tibial-femoral, the lateral tibial-femoral, and the patellofemoral. The knee joint is enclosed in a capsule lined with synovial tissue. The ends of the femur, tibia, and the undersurface of the patella are covered with a thin layer of hyaline cartilage. An additional piece of fibrocartilage helps cushion the medial compartment (medial meniscus) and lateral compartment (lateral meniscus). The knee is stabilized by internal structures such as the anterior cruciate ligament which prevents the tibia from sliding forward and the posterior cruciate ligament which prevents the tibia from sliding backward. Also, collateral ligaments, medial and lateral, prevent sideways slippage. Additional tendons and muscles provide further stability. Numerous blood vessels and nerves travel within and next to the knee. As with other regions, the knee may be affected by mechanical/degenerative processes (meniscus tear, ligament tear, osteoarthritis), inflammatory processes (rheumatoid arthritis, psoriatic arthritis, reactive arthritis, crystal-induced arthritis), infections, and tumors. Also, the knee pain may be referred. Arthritis in the hip typically causes pain referred to the knee. In addition, pinched nerves in the low back may cause pain referred to the knee. A history of recent trauma may suggest internal derangement due to disruption of a ligament or meniscus. A history of repetitive trauma, athletic, or occupational injury in the distant past may suggest more of an arthritic problem. Locking, clicking, give-way may indicate meniscal disease. However, loose pieces of cartilage (loose bodies) in the knee, cruciate ligament tear, or other processes may cause this also. Night pain indicates an inflammatory component. Evaluation of the knee should include range of motion assessment, comparison with the opposite knee, and determination as to whether an effusion (excess fluid in the knee) exists. Tests for knee stability are important. Sometimes local tenderness at the joint line may signify arthritis or meniscal disease. Localized tenderness and swelling may also indicate bursitis. Laxity of the knee points to a ligament injury. Fluid accumulation within the knee may lead to a Baker’s cyst behind the knee. The type of laboratory testing is dependent on the history and physical examination. Careful examination of joint fluid may be helpful. An elevated white blood cell count in the joint fluid indicates inflammation. Crystals of uric acid or calcium pyrophosphate point towards a crystal induced form of arthritis. All joint fluid should be cultured to rule out infection. X-rays are helpful for staging the severity of osteoarthritis. Calcium deposits may point to a diagnosis of pseudogout. Magnetic resonance imaging and arthroscopy are very sensitive and specific diagnostic tools. Treatment depends on diagnosis. Patients may benefit from anti inflammatory drugs, physical therapy, ice, and quadriceps strengthening exercises. Some braces also are helpful. Aspiration of fluid from the knee followed by glucocorticoid injection may be therapeutic. Patients with arthritis may benefit from arthroscopic treatment and injection of viscosupplements (gel-like lubricants). While some studies have discounted arthroscopy as a worthwhile treatment for arthritis affecting the knee, it still plays an important role in selected cases. Also, it is an excellent tool for evaluating the knee in research studies involving new arthritis medications. Patients with severe end stage arthritis will require joint replacement surgery.
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