4) Gout and pseudogout
Knee osteoarthritis can be caused by two different crystal deposits in the joint: gout and pseudogout. Gout is caused by a build-up of uric acid crystals, while calcium pyrophosphate crystals cause pseudogout. Both of these crystal deposits cause a sharp pain in the affected joint, typically the knee, and a range of other symptoms, including swelling and decreased range of motion.
The accumulation of crystals in the joint causes inflammation and irritation of the synovial tissue, resulting in pain. In addition, the crystals can obstruct the movement of the joint, leading to decreased range of motion and further pain. Left untreated, the accumulation of these crystals can lead to significant damage to the joint over time, including the destruction of cartilage and the formation of cysts.