Generally characterized by pain, stiffness, restricted movement and swelling of the joint. Joints can be damaged by contusion, sprains, dislocation and fractures involving the joint. Damage is caused to ligaments, capsules, and/or the cartilaginous surfaces of the joint. Arthritis (inflammation of a joint) is a common condition, and can be caused by bacteria, viruses or fungus, but also arise from rheumatic disorders, most importantly chronic rheumatoid arthritis. Arthrosis is wear of the cartilage of a joint caused by old age or incorrect stress on a joint. Tumours affecting joints usually originate from the cartilage or joint capsule. Joint conditions may also be congenital, involving incomplete or faulty development. Bone disorders often cause pain in the joints, and muscular conditions such as contracture can also affect them. If a joint is not used the ligaments, capsule and attached muscles shrink, which can cause permanent stiffness of the joint, and if it is severely affected it can become completely immobile (ankylosis). Loose piece of bone or cartilage in the cavity of a joint, which can cause pain when the joint is moved, and make the joint jam in a particular position. The condition occurs if a piece of bone or cartilage breaks off, or as a result of bone death caused by circulatory disorders such as osteochondritis. The condition is apparent on an X-ray of the joint. Treatment is by surgical removal of the piece as a matter of some urgency, because delay could lead to serious damage to cartilage and possible arthrosis.