Kohler disease is a condition that affects a bone at the arch of the foot called the tarsal navicular bone. X-rays show that this bone is initially compressed and later breaks into pieces before healing and hardening back into bone. Signs and symptoms of the condition include swelling, redness and/or tenderness of the affected foot which can lead to a limp or abnormal gait (style of walking). Although the exact underlying cause of Kohler disease is unknown, some scientists suspect that it may be caused by excessive strain on the tarsal navicular bone and its associated blood vessels before the bone is completely ossified (hardened).