B. Non-traumatic causes of knee pain
◘ Rheumatoid arthritis: Rheumatoid arthritis and other types of arthritis usually involve the knee at some point of the disease. Knee pain in rheumatoid arthritis slowly progresses and ultimately becomes a severe disability that won’t allow patients to walk or climb stairs. It usually appears in adults, but there are juvenile forms of arthritis that may affect children as well.
◘ Osteoarthritis: It is the most common type of arthritis that is associated with knee pain. Osteoarthritis is a degenerative type of arthritis, which means that it results from wear-and-tear of the articulation. It usually appears in older adults and progresses as the articulatory cartilage wears down and leaves the bony ends of the femur and the patella meeting and rubbing against each other with each movement.
◘ Post-traumatic arthritis: Some patients may develop a form of post-traumatic arthritis after a traumatic event in the articulation of the knee. The mechanism of disease is similar to osteoarthritis, usually related to degeneration of the joint surface leading to joint instability and progressive damage and wear down of the articulation.
◘ Gout: It is another form of arthritis that is based on the accumulation of uric acid crystals in the articulations. Gout is often associated with pain in the articulations of the lower extremities, especially the foot and the toes, but may also lead to knee pain. Similar to other forms of arthritis, patients with gout often have a swollen and reddened articulation associated with sudden and severe joint pain.
◘ Pseudogout: The mechanism of disease of pseudogout is similar to that of gout, but instead of uric acid crystals there are deposits of calcium crystals in the articulations.
◘ Bursitis/synovitis: When there’s an inflammation in the synovial membrane or bursa, knee pain may be prolonged, recurrent, and difficult to treat. Inflammation may be due to infectious diseases, and autoimmune reaction, or wear-and-tear of the articulation.
◘ Systemic Lupus Erythematous: There are also uncommon causes of knee pain, as in systemic lupus erythematous. This is an autoimmune disease that affects different body systems and tissues, and patients would have different symptoms depending on the type of SLE. Rheumatoid arthritis is often associated with SLE, and both conditions may ultimately lead to knee pain.
