Subastragalar refers to the ball of the ankle joint. The tarsal refers to one of seven bones of the ankle. Ankylosis is the immobilization and stiffness of a joint. In this case, the subastragalar or tarsal joint is involved.

Causes of ankylosis of the tarsal joint may include: congenital conditions such as tarsal coalitions; surgical arthrodesis; diseases of the bone or joint (e.g., arthritis); trauma (e.g., fractures); surgery; or from contractures due to prolonged immobility.

Manifestations of the condition may include: restricted motion of the joint (normal ROM for the ankle for ankle plantar flexion is 0 to 45°, and for ankle dorsiflexion 0 to 20°); pain; stiffness; or spasms of the tendons. Severe flatfoot deformity may be present (see Diagnostic Code: 5276 Flatfoot, acquired). Other signs and symptoms may include: pain or tenderness; swelling; deformity; or crepitus that may arise from joint disease such as arthritis.

Physical examination; range of motion tests (plantar flexion and dorsiflexion); as well as tests of the ligaments at the ankle and foot may be performed. X-rays, computed tomography (CT) scan, and magnetic resonance imaging (MRI) are used for diagnosis. A goniometer is used to measure range of motion.

Treatment may be conservative with immobilization, casting, or orthotics. Surgery may be indicated, depending on severity of pain and deformity. General treatment for ankylosis may include physical therapy, and maintenance of the joint in a functional position with range of motion exercises to affected joints (e.g., daily mobilization of the joint). If the ankylosis was surgically created, the joint is kept immobilized in correct body alignment for 6 to 12 weeks until the bone is healed. Medications and other therapies such as traction may be instituted to treat other conditions. Arthroscopy may relieve pain and increase mobility.

Surgical outcome for tarsal coalitions is good in about 75 to 90% of cases. Deterioration at the site of the joint may occur due to decreased activity. The possibility of long-term physical therapy exists.

• The rating schedule for musculoskeletal was updated on February 7, 2021. Protection still does apply and should be considered with existing evaluations (38 CFR 3.951(a)).

• None.