Ankles are joints that connect bones in the feet with bones in the lower leg. They are comprised of bones, ligaments, muscles, tendons, blood vessels, and nerves. The ankle joint allows the foot to move side-to-side, as well as up-and-down.

Ankle pain can be caused by a variety of conditions, but is most commonly due to soft tissue injuries such as ankle sprains and strains. 

An ankle sprain occurs when one or more of the strong ligaments that support and stabilize the ankle become torn if the ankle rolls, turns, or twists awkwardly. Depending on the grade of sprain (mild-moderate-severe), there will be varying degrees of pain, swelling, and restricted range of motion, along with tenderness, bruising, and ankle instability. There may even be an audible popping noise at the moment of injury.

Ankle fractures are another common source of ankle pain and occur one or more of the three bones in the ankle become fractured (broken). These breaks can be stress fractures (due to repetitive stress) or traumatic fractures (due to an acute injury). Depending on where and how severe the fracture is, symptoms can include pain and swelling that can sometimes spread up to the knee, bruising or discoloration, and an inability to bear weight. A visible deformity or exposed bone may occur in severe fractures.

Various forms of arthritis may also cause ankle pain. Rheumatoid arthritis (RA) causes the immune system to attack healthy joints, like the ankle joint, by mistake, causing stiffness and swelling in both ankles. Osteoarthritis occurs when cartilage covering the ends of bones wears down, causing the bones to rub against each other. This results in pain, stiffness, and reduced range of motion in the ankle. Gout is a form of arthritis where excess amounts of uric acid in the bloodstream crystallize and build up on joints, causing severe pain and swelling. Reactive arthritis causes joint pain and swelling in the ankle in response to an infection in another part of the body.

Other forms of ankle pain include bursitis (an inflammation of a cushioning bursa sac between tendons and bone), scleroderma (a thickening of connective tissues), chronic ankle instability (caused by improperly healed ankle sprains), Achilles tendon injuries, flat feet, or an infection in the ankle.