Arthritis of the hip or knee can occur for a variety of reasons. In most patients, arthritis develops due to simple wear-and-tear (also known as osteoarthritis), but genetics play a factor, and this condition does frequently run in families.
Inflammatory types of arthritis, such as rheumatoid arthritis or psoriatic arthritis, are generally immunologic conditions that cause progressive loss of cartilage and may present sooner in life. Finally, a previous injury or surgery in the hip or knee, or a longstanding deformity, may change the biomechanical environment of the joint and result in a progressive loss of cartilage.
Whether the cause is simple wear-and-tear, an immunologic condition, or post-traumatic in nature, arthritis of the hip or knee can be a crippling condition that in most patients is very treatable.