Ankle Sprain Differential Diagnoses

Updated: Jul 24, 2017
  • Author: Craig C Young, MD; Chief Editor: Sherwin SW Ho, MD  more...
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DDx

Diagnostic Considerations

Fracture

An individual with an ankle sprain can almost always walk on the foot, albeit carefully and with pain. In an individual with normal local sensation and cerebral function, the ability to walk on the foot usually excludes a fracture.

No bony point tenderness should be present; pay particular attention to the medial malleolus, lateral malleolus, base of the fifth metatarsal, and midfoot bones. Point bony tenderness at one of these areas, as well as bony deformity or crepitus, suggests the possible presence of a fracture.

The Ottawa foot and ankle rules can be reliably used to exclude fractures in children older than 5 years and has been suggested as possibly accurate for children as young as 2 years. [8, 9]

Neurovascular compromise

Suspect neurovascular compromise if the patient complains of a cold foot or describes paresthesias. [1] Bone tenderness in the posterior half of the lower 6 cm of the fibula or tibia and the inability to bear weight immediately after the injury and in the emergency department are indications to obtain radiographic imaging.

As with all limb injuries, the neurovascular status of the limb must be assessed. This assessment consists of palpation of the dorsalis pedis and posterior tibial arterial pulses. Testing for sensation, especially over the sural nerve distribution, is also necessary; sural nerve and peroneal nerve palsies, although rare, may complicate a lateral ligamentous injury. Electromyographic examinations of individuals with severe ankle sprains have shown that 80% of these patients have some degree of peroneal nerve injury.

Continued pain after rehabilitation

If pain persists despite rehabilitation, diagnoses to consider include the following:

  • Intra-articular meniscoid lesions represent localized fibrotic synovitis in the lateral ankle following inversion sprains; the condition also is known as impingement syndrome.
  • Peroneal tendon subluxation is due to detachment of the peroneal retinaculum from its normal insertion on the posterior border of the fibula to the lateral surface of the fibula.
  • Talar dome fracture occurs with inversion and eversion injuries, but it may not be readily seen on radiographs.
  • Anterior process fracture of the calcaneus occurs with inversion injuries. Patients commonly display bony tenderness rather than ligamentous point tenderness.
  • Complex regional pain syndrome (CRPS), or reflex sympathetic dystrophy, can develop after ankle sprains. The reason for this is unknown; however, the condition may arise from an abnormal response to disuse and/or splinting of the foot and ankle. Early, controlled activity and rehabilitation may prevent the development of CRPS.

Other factors

Active ROM must be assessed, because Achilles tendon ruptures can mimic ankle sprains. Extensive swelling, ecchymosis, or pain may suggest an osteochondral lesion not observed on plain radiographs. CT scanning is useful for evaluating osteochondritis dissecans and stress fractures. MRI may be useful when osteochondrosis or meniscoid injury is suspected in patients with a history of recurrent ankle sprains and chronic pain. [6] A bone scan can detect subtle bone abnormalities (eg, stress fracture, osteochondral defects). A bone scan can also detect syndesmotic disruption.

Differential Diagnoses