How To Diagnose Lateral Ankle Injuries

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

Recognizing Potential Nerve Injuries

   Nerve injuries are often the last category of injury clinicians consider when diagnosing lateral ankle problems. Nerve symptoms may include pain, burning, tingling or numbness. The symptoms will often radiate distally or proximally. The symptoms may or may not be related to activity but will often relate to the position of the foot or pressure from shoes.38    Any inversion injury has the potential to place traction on the sural nerve as it runs alongside the peroneal tendons. Additionally, the superficial peroneal nerve becomes superficial in close proximity to the anterior talofibular ligament and may become partially entrapped in scar tissue as injury to the ligament heals. Blunt trauma may cause direct injury to the nerve itself, resulting in neuropraxia.    Patients may complain of sharp pain with sudden pivoting movement or any compression of the anterior of the lateral ankle, which may occur in high-topped boots or ski boots.39 Other complaints may consist of either transient or constant numbness, and periodic tingling or burning sensations. Symptoms may be worse at night than during the day. More serious injuries, such as plantarflexion inversion injuries, may result in traction injury to either the sural or common peroneal nerves, leading to axonotemesis or neurotemesis, depending on the severity. Specifically, plantarflexion inversion injury causes constriction of the peroneus longus at the level of the common peroneal nerve, entrapping the nerve as it passes underneath the muscle.    Physical exam findings may indicate allodynia, decreased sensation to light touch, an inability to distinguish between sharp and dull stimuli and decreased two-point stimulation. Manual percussion of the affected nerve precipitates distal paresthesias (positive Tinel’s sign) or more infrequently proximal paresthesias (positive Valleix’s sign).5,40 Swelling about the affected area is rarely present. Severe injuries of the common peroneal nerve may cause paralysis and muscle atrophy, leading to foot drop.5,41    More sophisticated diagnostic studies are often necessary, particularly when it comes to distinguishing between local nerve injury and a possible correlation to any associated or past low back injury. One should suspect radiculopathy in any patient who exhibits positive proximal findings, particularly in a positive straight leg raise test. Electrodiagnostic studies, including nerve conduction studies, may be key in ruling out radiculopathy or mononeuropathy in these patients.5,39

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