MRI For Ankle Sprains: When Is The Time?

I typically see about five to ten ankle sprains a week in my practice. While the vast majority of these patients do well with conservative therapy alone, there are about 10 percent who return to my office after six weeks of physical therapy with continued pain and discomfort. I usually will not hesitate to order magnetic resonance imaging (MRI) at this point for evaluation of other possible pathologic processes. While some may argue that this is too soon and that ideally the ankle sprain patient may continue to show signs of improvement until the 10-to-12 week mark, I would argue that missing an injury other than a partial tear of one or multiple ankle ligaments is not worth the wait! Here are several injuries that may masquerade as a simple ankle sprain.

One or both of the peroneal tendons may be partially, or in rare cases completely torn as part of an ankle injury presenting as a standard Grade 1 or 2 ankle sprain upon initial evaluation. This may contribute to unresolving pain and discomfort after an initial course of physical therapy. Continued pain to the posterior aspect of the fibula can also be a sign of retinacular tearing, especially on dorsiflexion and eversion with forced resistance which can reproduce dislocation of the peroneals and confirm this diagnosis.¹ Further imaging can give the surgeon a more detailed understanding as to the involvement of the tendons, as well as the degree to which the superior peroneal retinaculum is damaged to guide operative intervention.

Osteochondral lesions (OCLs) of the talus can also be a contributing factor for why a “simple sprain” continues to be symptomatic. It is estimated that up to 50 percent of ankle sprains may have some degree of chondral damage.² While most of these injuries likely resolve on their own and few require further evaluation and treatment, it is important to have OCLs as part of your differential diagnosis so as to not miss a potential reason why your patient with an ankle sprain continues to have pain and discomfort. It is also important to also be on the lookout for other signs of an OCL such as locking or sudden pain to the ankle irrespective of activity or motion. MRI can be a great modality for diagnosis and surgical planning in these cases and early diagnosis can play a major role in the patient's outcome.

Ankle instability can also be another cause of continued ankle pain after a sprain. A detailed history in the initial work-up is key when evaluating these patients and I always ask if there is a history of multiple ankle sprains. Additionally, I try to ascertain how often/how easily they feel they sprain their ankle or the ankle gives out on them. I find identifying an acute-on-chronic issue is key to further management. In these patients I have a low threshold for ordering advanced imaging, but will await to obtain the imaging after a course of PT and allowing the initial inflammatory process of the new sprain to “calm down” before doing so.³

While there are other pathologic processes that can cause continued ankle pain in a patient who presents for evaluation of a sprain in the initial setting, in my experience, these are some of the more common reasons. A detailed history and physical exam can be helpful in teasing out other reasons for continued pain and in these scenarios, I have a low threshold for advanced imaging in the form of an MRI. I hope this helps you and your patients as well to not miss a more complex problem when a simple sprain does not heal.

Dr. Ali Rahnama is a fellowship-trained foot and ankle surgeon and an Assistant Professor at the Georgetown University School of Medicine in Washington, D.C. You can follow him on Instagram @DrAliRahnama for interesting cases and educational material. 

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References

1. Heckman DS, Reddy S, Pedowitz D, Wapner KL, Parekh SG. Operative treatment for peroneal tendon disorders review. J Bone Joint Surg. 2008;90(2):404-418.

2. Saxena A, Eakin C. Articular talar injuries in athletes: results of microfracture and autogenous bone graft. Am J Sports Med. 2007;35(10):1680–1687.

3. Cao S, Wang C, Ma X, Wang X, Huang J, Zhang C. Imaging diagnosis for chronic lateral ankle ligament injury: a systemic review with meta-analysis. J Orthop Surg Res. 2018;13(1):122.