By Robert C. Olson, D.P.M.
It is estimated that 25,000 people sprain their ankle every day in the United States. Approximately 85% of these injuries are a rolling in or inversion of the ankle. Typically the ligaments on the outside of the ankle are stretched or torn. Sprains can be divided into 3 levels or grades of injury, which correlate with the level of ligament damage, based on clinical exam. Grade II and III injuries consist of partial or complete tearing of the ligaments. Treatment begins with RICE (rest, ice, compression, elevation) and includes immobilization in grade II and III injuries to allow healing, followed by rehabilitation to prevent repeat sprains. Often patients are told to begin activity too early or don’t seek treatment at all. Twenty to thirty percent of patients suffer long-term effects from their injury. This is generally chronic pain along the outside of the ankle. The four most common causes of pain following an ankle injury are: impingement, peroneal tendon tear, osteochondral defect of the talus, and ankle instability.
When the ankle ligaments are damaged the joint capsule or lining of the ankle may also be torn. This tearing may lead to scarring within the ankle that gets pinched between the leg bone and foot bone of the ankle during walking or activity. This causes pain along the front of the ankle, which may come and go with certain activities. Magnetic resonance imaging (MRI) is a test that may aid in the diagnosis of this problem, but the scarred tissue isn’t always seen clearly. Steroid injections will often give temporary relief, but generally ankle arthroscopy or a “scope” is done to remove the abnormal soft tissue and allow return to activity.
Peroneal tendon tear
There are two tendons that run behind the fibula or outside ankle bone called the peroneus brevis and peroneus longus. When the ankle turns inward as in a typical ankle sprain the peroneus brevis can be pressed against the fibula causing it to tear or split like a hot dog. If detected early these tears may heal with 5-6 weeks of immobilization, if not they may cause chronic pain along the back of the ankle. This diagnosis is typically made based on clinical findings, but an MRI may aid in the diagnosis. In most patients who have had a tear for several weeks or months, it is difficult to get them to heal with a cast or cast boot. These patients often require surgical repair of the torn tendon.
Osteochondral defect of the talus
The talus is the foot bone of the ankle. This injury is a broken piece of cartilage, which may be attached to a small piece of underlying bone from the talus. These injuries most commonly affect the outside of the ankle. Patients with these injuries complain of a pain deep within their ankle. They may also have some catching and painful clicking or popping with activity. If the piece of bone is very thin it may not be visible on x-ray. MRI of the ankle will typically show this pathology. Unless the attached piece of bone is very thick, these broken pieces of cartilage and bone need to be removed from the ankle. This can typically be done through the scope, occasionally the ankle joints need to be opened for removal.
Instability of the ankle can be divided into mechanical and functional instability. With functional instability the ligaments are not stretched and the ankle is stable on exam. The patient, however, has the feeling of giving way. This can be caused by the above-mentioned problems or by instability from improper muscle function. This is treated with physical therapy for rehabilitation and retraining of the ankle. Mechanical instability, on the other hand, is due to improper healing or stretching of the ankle ligaments that cause the ankle to be unstable or lax, leading to the true giving way of the ankle. This can be controlled in some patients with bracing, but often times surgical repair or reconstruction of the ankle ligaments is necessary.
The problems discussed above are certainly not the only causes for ankle pain, however, they are the four most common causes for pain following what may otherwise may have been thought of as “just an ankle sprain.” Although these problems are common they don’t need to be considered normal or expected.