A hammer toe is a deformity of the proximal interphalangeal joint of the second, third, or fourth toe causing it to be permanently bent, resembling a hammer. Hammer toe most frequently results from wearing poorly fit shoes that can force the toe into a bent position, such as excessively high heels or shoes that are too short or narrow for the foot. Having the toes bent for long periods of time can cause the muscles in them to shorten, resulting in the hammer toe deformity. This is often found in conjunction with bunions or other foot problems. It can also be caused by muscle, nerve, or joint damage resulting from conditions such as osteoarthritis, rheumatoid arthritis, stroke, Charcot-Marie-Tooth disease or diabetes.

In many cases, conservative treatment consisting of correcting the foot structure, and new shoes with soft, spacious toe boxes is enough to resolve the condition. While in more severe or longstanding cases orthopedic surgery may be necessary to correct the deformity. The chiropodist may also prescribe some toe exercises that can be done at home to stretch and strengthen the muscles.