As the name implies, crab pincer toenail resembles a crab’s pincer, wide at the back and narrow and bulging at the front, piercing the flesh in front and on both sides of the toe, causing great problems in walking and movement, pain, and greatly reducing the quality of life. The following is an in-depth description of this toenail deformity. Prevalent in the big toe, it usually has four etiologies: 1. Hereditary 2. Acquired – caused by foot deformity. 3, Acquired – due to skin disease. 4. Acquired – due to degenerative osteoarthritis of the distal interphalangeal joint. Congenital crab toenail is almost always symmetrical in onset, and other family members may have the same condition. The most common cause of an over-curved toenail is an enlarged base of the distal phalanx. Radiographs always show an enlarged base of the distal phalanx with a bony tubercle pointing distally, and distraction warts are often seen on the radiographs. Surgical treatment is the only option. A more complete treatment usually requires a combination of nail root, tuberosity and nail bed reshaping to obtain a more satisfactory result.