The most common cause of pain on the outside of the foot is an injury due to a trauma of some sort. Athletes often feel pain that may be the result of an impact, muscle strain, ligament sprain, or tendon inflammation. Other common causes of pain on the outside of the foot include bone fractures, bursitis, bunions, or skin problems such as blisters or split and cracked skin. Very often such pains are the result of footwear that does not fit correctly, or as a result of an improper walking or running gait. Sometimes a gait analysis and correction can help reduce pain on the outside of the foot.
Tendons are fibers that connect muscles to bone. When these tendons become irritated for any reason, the resulting condition is known as tendinitis. This can occur in various locations throughout the body, and it can cause pain on the outside of the foot when the foot tendons become inflamed due to an incorrect gait or poorly fitting footwear. Wearing shoes that are slightly wider can often help alleviate tendinitis in the foot, and choosing footwear that is properly cushioned and designed to support the arch of the foot can help prevent pain resulting from tendinitis.
The feet absorb a significant amount of strain from day to day activities such as walking or running, so when the muscles and tendons absorb a shock they cannot handle, the bones are left to absorb the residual shock. If the bones cannot absorb that residual, they may crack, or fracture. Fractures can be quite small and still cause a significant amount of pain; smaller fractures often heal on their own when allowed plenty of rest and immobilization, though larger fractures will need attention from a medical professional. Severe fractures may require surgery to repair.
Bursitis occurs when a bursa, a fluid filled sac that helps cushion movement between muscles, ligaments, and bones, becomes inflamed. This inflammation can cause rubbing and pressure throughout the foot, or more locally near the site of the bursa. This inflammation is often due to some sort of unnatural movement or pressure and can be alleviated with anti-inflammatory medications as well as corrections in walking gait or footwear changes.
A bunion, or small bone growth, can develop on the outside of the foot near the smallest toe, causing pain on the outside of the foot. These are usually genetic, and if they cause severe pain, they will have to be addressed surgically. Wearing footwear that accommodates this growth can also help alleviate the pain without surgery.