Hip joint degeneration. Sequence of illustrations showing progression from mild to advanced arthritis in a hip joint. Upper left: inflammation of synovial membrane; upper right: pannus formation; lower left: destruction of cartilage; lower right: bony ankylosis. Joint tissues include cartilage (pink), the synovial membrane (blue), and the joint capsule (orange). Osteoarthritis is a joint disease aggravated by mechanical stress. Symptoms include joint pain, stiffness and swelling. This sequence also shows the progression of osteoporosis, where bones become brittle and prone to fracture. For the individual images, see C029/0663-66.