Ankylosis is a medical condition that occurs when bones fuse in a joint. The fusion can be complete or partial, and it leads to severe rigidity of movement. Symptoms of the condition include pain in the joint and a limited range of motion. Ankylosis can be caused by various diseases, such as arthritis and certain forms of gangrene, and it also can be caused by traumatic injury and inflammation. The condition can happen anywhere in the body where bones meet at a joint.
With so many possible triggers of this condition, the exact underlying cause is not always well understood. The place where bones meet is called a joint. Bones are supposed to sit relatively loose at that joint, which allows for a full range of motion in areas such as the shoulders, knees, hips and other bone-joint pairings. Ankylosis occurs when bones grow too large via a process known as ossification, the multiplication of bone cells. As the bones grow across the joint, they will fuse, reducing the range of motion.
There are several common forms of the condition. One of the most widespread forms is ankylosis of the temporomandibular joint, where the jaw connects to the skull. It typically is caused by an infection, by a tumor or as a complication of a traumatic wound that did not heal properly. It also can be a congenital disorder.
Another form is ankylosing spondylitis, which affects the spine. It is a chronic condition that involves constant inflammation of the spine and the sacroiliac joint, a joint in the pelvis that supports the bottom of the spine. If left untreated, this condition can lead to the spine fusing to the pelvis, ending in a loss of mobility in the spine. This particular form is usually genetic.
The treatment depends on the location of the disorder. In the jaw, simple jaw exercises may be prescribed to help decrease rigidity. Similar forms of physical therapy also can be used in mild cases of hip and knee ankylosis.
There also are medications that can treat the disorder, especially if the main cause is inflammation. Surgery can be used to remove the excess bone growth. In some cases, if the doctor believes that ankylosis will continue after the first bone mass is removed, a prosthetic bone might be implanted at the joint end.
It also is possible to create an artificial form of the condition. Doctors can induce bone growth across a joint, causing two bones to fuse. Termed arthrodesis, it is used to help heal fractures and ease the pain of arthritis. This procedure typically is used only if other forms of pain medication and joint replacements have failed.