How To Diagnose Lateral Ankle Injuries

By Remy Ardizzone, DPM, and Ronald L. Valmassy, DPM

   Many of these subtle injuries heal uneventfully. Occasionally, however, the patient will complain of persistent pain posterior to the lateral malleolus that is exacerbated by lateral cutting maneuvers such as the swift side-to-side motion one frequently sees in tennis or soccer, or abrupt changes in direction that occur when pivoting on one foot. Swelling may or may not be present but one may frequently reproduce pain via palpation of the tendons posterior to the lateral malleolus and through resisted ankle eversion.

   Frequently, clinicians may see evidence of a tear on a MRI as indicated by a C-shaped appearance to the tendon on an axial projection with abundant scar tissue formation surrounding the tendon and increased fluid signal on T2 STIR sequences.28,30,31,32 Magnetic resonance imaging may also help distinguish between a discrete tendon tear and less serious conditions of tendonitis or tendonosis although chronic tendonosis may be a precursor to an actual tear.30 Comparing T1 and T2 images at the distal tip of the fibula will help clarify potential “false positive” findings due to the magic angle phenomenon.28,31 Bear in mind that a normal study does not preclude surgical intervention under appropriate clinical circumstances.

   However, one cannot appreciate peroneal tenosynovitis on MRI. In order to diagnose this condition, which involves hypertrophic synovium within the peroneal tendon sheath within the tendons themselves, one should use a tenogram.33 When the tenogram is positive, the flow of radioopaque dye will be impeded by adhesion or stricture of the sheath or scar tissue about the tendon.34 Additionally, a tenogram may be potentially therapeutic as well as diagnostic. The mixture of local anesthetic and radioopaque dye into the closed space of the tendon sheath acts as a “balloon” to separate the adherent scar tissue from the surface of the tendon. Adding corticosteroid into the injection may potentially “shrink” any adhesive scar tissue and decrease inflammation. Given the risk of tendon rupture with corticosteroid injection to tendons, this procedure requires a skilled radiologist to ensure an injection into the space between the tendon sheath and the actual tendon itself.

   Subluxation of the peroneal tendons may occur for anatomical reasons or as a result of an inversion injury but the subluxation is often overshadowed by a lateral collateral ligament injury.35 During an inversion injury and particularly following repeated ankle sprains, the peroneal retinaculum may be stretched and no longer retain the tendons posterior to the lateral malleolus.26,27 If the patient has an anatomically shallow fibular groove, then even a subtle injury to the retinaculum may cause the tendons to slide anteriorly.34,36 Recent studies also suggest that a more posterior anatomic position of the fibula may also contribute to instability, influencing the ability of the peroneal tendons to stabilize the ankle.37

   Patients will often complain of sudden sharp pain to the lateral ankle with lateral cutting maneuvers, pivoting or rising onto the balls of the feet.34 Swelling may or may not be present. Often, during the physical exam, the physician can feel the tendons snap or slide anterior to the fibula by palpating the area while the patient either rotates the foot in a circular motion or rises onto the balls of the feet. One may not appreciate subtle sliding of the tendons on examination. Obtaining a MRI can aid in diagnosis since it will show evidence of stretching or scarring of the peroneal retinaculum as well as decreased concavity of the peroneal groove.6,7,26,28-30

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