The small muscles running down the front of the leg below the knee are known as the extensor muscles. The extensor hallucis longus (EHL), and the extensor digitorum longus (EDL), are the two main muscles in this group. Their tendons cross the ankle and insert into the toes. Together, the extensor muscles bring the toes and foot up toward the shin, in direct opposition to the larger calf muscles, which point the toe. Tendonitis occurs when the tendons, or cord-like attachments of the muscle to bones, become inflamed and irritated, usually due to overuse.
Rest
The primary treatment of any tendonitis should start with a rest period, resting the affected foot as much as possible and avoiding activities that stress the extensor tendons, such as running on hills and stair climbing. Ice and NSAIDs will help with any swelling accompanied with the tendonitis.
Stretching and Strengthening
Tight calf muscles are one of the leading causes of extensor tendonitis. While tight calves are common in athletes such as runners, regular stretching helps to build flexibility and prevent irritation to the extensor tendons. Wall stretches for the large gastrocnemuis muscles and step stretches for the smaller soleus muscles typically work well. Once the initial period of irritation and pain ends, gradual strengthening of the extensor muscles will help recurring tendonitis from flaring up.
Orthotics
Sometimes, extensor tendonitis may be caused by a flat foot, a condition that occurs when the normal arch of the foot falls. When this happens, it puts additional strain on the extensor muscles during activities using the legs. In these cases, using shoe inserts to help regain the correct gait will help tendonitis from recurring.