A common foot injury often misdiagnosed as a complex ankle sprain is called peroneal tendonitis. The peroneal tendons are two in number, and run together under the outside of the ankle joint, where they stay together for a couple inches until they reach the middle part of the side of the foot. It is here that one stays on the side of the foot, attaching to the bone prominent on the outside of the foot. The other longer tendon runs underneath the foot to attach near the other side. These tendons are known as everters, because they help the foot to roll to the outside, or evert. This motion is very important during the normal walking cycle, and helps to balance the more powerful muscles on the other side of the foot that draw it inward.
The peroneal tendons can become injured during simple ankle sprains, as the twisting force that tears ankle ligaments can stretch and injure the peroneal tendons running near the ligaments. However, the peroneal tendons can also become injured without having a specific sprain. Walking on uneven surfaces, simple excessive climbing, using unstable shoes, and even compensating for arch pain can lead to peroneal tendonitis. Because the symptoms, which may include pain around and under the outside of the ankle, are similar to the pain of an ankle sprain, it is often misdiagnosed as an ankle sprain. The typical pattern of pain also includes sharp or achy pain to the side of the foot, where the majority of the time the pain is at it’s strongest. Bearing weight on the injured foot, twisting it inward, and moving on uneven ground like lawns or gravel can aggravate the pain. There is rarely ever swelling or bruising visible on the side of the foot, and there is never a cracking or popping sensation (unless the tendons are moving over the ankle bone or a fracture has occurred on the side of the foot- both of which are different conditions).
Fortunately, the treatment of peroneal tendonitis is not too different from that of an ankle sprain, so if there is a misdiagnosis at least the recovery process is similar. In general, peroneal tendonitis needs rest, ice, anti-inflammatory medications, and ankle brace support. Cases that don’t respond to these measures need physical therapy to help with healing and strengthen the tissue. The difference in treatment from an ankle sprain lies in that if physical therapy is needed to improve the recovery, a misdiagnosis could lead to imprecise therapy and a poor result. In addition to the above treatment, severe cases of peroneal tendonitis may require immobilization of the leg or surgery to repair the tissue damage. It is not uncommon for partial tears of the tendon to accompany the tendonitis, and often these need to be surgically repaired if the pain is not resolving with non-surgical treatment.