Genetics

• Some researchers believe that ankylosis is caused by a gene mutation. Studies point to a progressive "ank" gene believed to amplify or generate excess osteoblasts, or bone cells, leading to the condition. It is also believed that a tendency toward ankylosis runs in families and is more common in men between the ages of 20 and 40 than women.
  
  

Injury

• Trauma or injuries to bones and joints may also lead to ankylosis. Joint ankylosis is also believed to be caused by repeated episodes of bleeding, as found in patients diagnosed with hemophilia.
  
  

Rheumatoid Arthritis

• Rheumatoid arthritis and osteoarthritis are also suspected of causing ankylosis. A continued inflammation of connective joint tissues destroys synovial membrane, cartilage and chondral bone structures. The resulting damage brings stiffness and reduces mobility in the joint.
  
  

Infection

• Infection in a joint may also lead to ankylosis, depending on damage to connective tissues such as the bone, cartilage, fluid, blood vessels and nerves found within a joint. Damage to any of these may cause stiffness, while lack of blood flow causes joint tissues to slowly die. Degeneration of bony tissues results in a lack of motion, which may be defined as ankylosis.
  
  

Immobility

• Immobility or long-term misuse of an extremity or body part may eventually lead to ankylosis of the bone joints. People on long-term bed rest or those suffering who must use a wheelchair over time may notice extremities growing stiff due to misuse. Range of motion exercises can reduce stiffness and eventual bone fusion.