Lateral ankle pain and hindfoot conditions can be difficult to diagnose through a history and physical exam. Often, multiple anatomic areas are painful with palpation or motion. To that end, it is common to order magnetic resonance imaging (MRI) for a “lateral ankle pain.”
We commonly diagnose and confirm peroneal tendon disorders through MRI. To make things challenging, it has been my personal experience that MRI findings of peroneal tendon pathology are often misleading. Incidental findings of a peroneus brevis tendon split tear, for example, occur with regularity.
It is not uncommon for a patient to be referred by a primary care physician or another podiatrist to my office with a MRI report in hand and a chief complaint of “tendon rupture … and I need surgery now.” Typically, these patients do not need surgery for their “tendon rupture.”
Since I know that MRI findings of peroneal tendonopathies are unreliable, the physical exam is very important. I spend extra time with careful palpation and muscle testing of the peroneal tendons. I want to be positive without a shadow of a doubt that the patient’s pain symptoms are caused by peroneal tendon pathology rather than something else such as ligament derangement, an osteochondral lesion of the talus or lateral ankle joint impingement/arthritis.
During the physical exam, one should perform a careful examination of the peroneal tendon course. I pay particular attention to five zones. These zones include: the retromalleolar region where peroneal tendinitis (overuse injuries) are common; the tip of the fibula, which is a common area of stenosing peroneal tenosynovitis in the cavus foot type; the peroneal tubercle, which can cause irritation to the peroneus brevis tendon; the cubital tunnel; and the base of the fifth metatarsal. Most of the peroneal tendon tears will occur between the fibula and the fifth metatarsal base. Typically, there will be impressive edema when there is a tendon rupture or partial tear.
X-ray findings may aid in the diagnosis. The presence of an os peroneum, especially one that is irregular or has multiple fragments, may be an indication of peroneus longus pathology. Triangulation of the base of the fifth metatarsal may be an indication of a degenerative process of the insertion of the peroneus brevis tendon. Patients with metatarsus adductus, especially those with a cavus foot type, are known to have lateral foot and ankle pain with “wear and tear” on the lateral column of the foot.
I performed a simple retrospective study on peroneal tendon pathology and the significance of MRI, and recently lectured about this in Phoenix for the Podiatry Institute. I collected data on patients with a primary diagnosis of either Achilles tendon or posterior tibial tendon pathology who required an MRI to aid in the diagnosis. I excluded any patient who had subjective or objective findings of any lateral ankle or lateral foot pain. I reviewed 42 patient charts and a board certified musculoskeletal radiologist interpreted all MRIs.
Thirteen of the 42 patients (30.95 percent) had pathology of the peroneal tendons on MRI without any clinical evidence/correlation. Of those 13 patients, six (46 percent) had isolated peroneus brevis conditions, five (38 percent) had isolated peroneus longus disorders, and two (15 percent) had disorders of both tendons.
In summary, peroneal tendon disorders are probably more common than the literature suggests. It is my opinion that chronic asymptomatic conditions, such as partial tears and tendinosis of the peroneal tendons, most commonly occur with the cavovarus foot type. In addition, I have been able to immobilize and rehabilitate patients with acute peroneal tendon injuries (including split tears) without surgical intervention.
Therefore, in my experience, patients with peroneal tendon injuries have the potential to recover without surgery. As a result, it is not surprising that many of the peroneal tendon pathologies are incidental findings on MRI. One should reserve surgical treatment for peroneal tendon pathologies that are symptomatic.