Osteoarthritis is a degenerative type of arthritis that occurs most often in people 50 years of age and older. In osteoarthritis, the cartilage in the hip joint gradually wears away over time. As the cartilage wears away, it becomes frayed and rough, and the protective joint space between the bones decreases. This can result in bone rubbing on bone. To make up for the lost cartilage, the damaged bones may start to grow outward and form bone spurs (osteophytes). Osteoarthritis of the hip causes pain and stiffness. Osteoarthritis develops slowly and the pain it causes worsens over time. The pain can radiate down the buttocks to the knee. Stiffness in the hip joint makes it difficult to walk or perform daily activities.