These injuries include stress fractures and tendonitis, and bone and heel spurs. Other common problems are blisters, bunions, corns, calluses, athlete's foot, Morton's neuroma, and black and ingrown toenails. Problems due to abnormal skeletal structure and stress on muscles are the most common cause of overuse injuries of the foot. They may not cause injury during normal activity, but excessive sports activity will make the problem worse. Such problems include flat feet and high arches.
Some people have naturally flat feet or feet that turn in when they run.
These people tend to walk and run on the insides of their feet. Doing this too much may cause overuse injuries such as stress fractures and tendonitis. It also makes the legs rotate inward. This can cause bursitis in the hip and kneecap pain. Shoe inserts do not help hammertoes.