Hip joint bony ankylosis. Illustration showing bony ankylosis (fusing of the bone tissue in a joint), the final stage in the progression from mild to advanced arthritis in a hip joint. 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 of images also shows progression from mild to severe osteoporosis, where the loss of calcium causes bones to become brittle and prone to fracture. For the individual images, see C029/0663-66. For all four images together, see C029/0667.