Osteoarthritis usually occurs in patients over 50 years old, and very often they will have a family history of arthritis. The cartilage in the knee that acts as a cushion for the bones thins out and wears away. This, in turn, allows for the bones to rub together causing pain and stiffness. Rheumatoid arthritis is a disease which there is thickening and inflammation of the synovial membrane. Over time this chronic infammation can cause cartilage damage, leading to pain and stiffness.
Traumatic arthritis can follow a serious knee injury.
Fracture or ligamentous injuries may damage the articular cartilage over time, causing knee pain. As your knee pain and stiffness increases, simply walking or climbing stairs can hurt. Conservative treatment is always attempted first. You also need strong muscles and ligaments for stability, because your knee is more than a simple hinge joint. Each time you bend your leg to walk or climb stairs, the bones rotate, roll, and glide on each other.