The ankle has two joints, one on top of the other.

The tibiotalar (top ankle) joint is composed of three bones, the tibia (shinbone), the fibula (the other bone in the lower leg), and the talus (anklebone). The leg bones form a scooped pocket around the top of the anklebone. This allows the foot to bend up and down.

The subtalar (bottom ankle) joint is where the anklebone connects to the calcaneus (heel bone). This joint enables the foot to rock from side to side.

Three sets of fibrous tissues connect the bones in the ankle and provide stability to the ankle joints.

Common problems affecting the ankle include sprains, Achilles tendon injury, fractures, and arthritis.

Sprain–Occurs when a ligament is forced to stretch beyond its normal limit. Usually happens when the foot twists, rolls, or turns beyond its normal motions. Symptoms include pain and swelling. The amount of pain depends on the amount of stretching and tearing of the ligament. Sprains fall into three categories:

• Grade 1 sprain–A mild sprain; slight stretching and some damage to the fibers (fibrils) of the ligament.
• Grade 2 sprain–A moderate sprain; partial tearing of the ligament.
• Grade 3 sprain–A severe strain; complete tearing of the ligament; instability can result.

Achilles tendon injury–Occurs when the tendon that connects the muscles in the lower leg to the heel bone gets overstressed, causing a strain (Achilles tendonitis) or a rupture. A direct blow to the foot, ankle, or calf can also cause this injury.

Fracture–A break in the bone. Can be caused by a fall, an automobile accident, or some other trauma to the ankle. Surrounding connecting tissue (ligaments) can be injured as well. Symptoms include immediate and severe pain, swelling, bruising, tenderness to the touch, inability to put weight on the injured foot, and deformity, particularly if there is a dislocation as well as a fracture.

Stress fracture–A type of overuse injury that occurs when fatigued muscles are no longer able to absorb the shock of repeated impacts. The muscles transfer the stress to the bones, creating small cracks or fractures. Stress fractures can also occur with normal usage if osteoporosis or another disease weakens the bones. Symptoms include pain that develops gradually, increases with weight-bearing activity, and diminishes with rest; swelling on the top of the foot or the outside ankle; tenderness to the touch; and bruising.

Chronic lateral pain–Recurring or persistent pain on the outer (lateral) side of the ankle. Symptoms include difficulty walking on uneven ground or in high heels, a feeling of giving way (instability), swelling, stiffness, tenderness, and repeated ankle sprains. The most common cause is incomplete healing after an ankle sprain. Other causes include injury to the nerves passing through the ankle, a torn or inflamed tendon, arthritis of the ankle joint, a break (fracture) in one of the bones that makes up the ankle joint, inflammation of the joint lining (synovium), and the development of scar tissue in the ankle after a sprain.

Arthritis–Types of arthritis that affect the ankle include osteoarthritis, rheumatoid arthritis (RA), gout, ankylosing spondylitis, psoriatic arthritis, and Reiter's syndrome.

• Osteoarthritis–The most common form of arthritis, this develops with age. Over time, the thin covering on the ends of bones (cartilage) becomes worn and frayed, resulting in inflammation, swelling, and pain in the joint. Symptoms include pain or tenderness, stiffness or reduced motion, swelling, and difficulty walking.
• Rheumatoid arthritis–A systemic disease that occurs when the body's immune system turns against itself, producing substances that attack and inflame the joints. The most common symptoms are pain, swelling, and stiffness. When the ankle is affected, the bones may shift position in the joints. This can cause the long arch on the bottom of the foot to collapse (flatfoot), resulting in pain and difficulty walking.

Source: American Association of Orthopaedic Surgeons