Os Trigonum: A Detailed Case Study

Student Author(s)

Brooke Dippel

Faculty Mentor(s)

Professor Margaret Frens

Document Type


Event Date



Os Trigonum, a small boney growth on the posterior aspect of the talus, is a syndrome that affects 10% of the general population. Although often asymptomatic, the active population may experience pain, such as athletes participating in soccer, football, and wrestling. Individuals with a rigid mid-foot or repetitive plantar flexion movement are predisposed to this syndrome. Categorized four ways for identification and treatment, Os Trigonum forms through chronic over-use injuries, traumatic acute injury, or through secondary processes. These categories include a normal presentation, elongated posterior talar process, presence of an accessory bone, and a fused Os Trigonum bone. Symptoms of Os Trigonum include stiffness, weakness, swelling, decreased plantar flexion, posterior deformity, and pain with general ankle movement. The gold standard used is MRI imaging and a full symptoms assessment. Differential diagnoses include Flexor hallicus longus tendinitis, lateral ankle sprain, tarsal tunnel syndrome, subtalar pathology, peroneal tendinopathy, Achilles tendon bursitis, or Osteochondritis dissecans of the talus. The detailed review of a specific case provides a further explanation of this orthopedic complication.

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