Background: Fifth metatarsal basis fractures are the most commonly seen fractures of the foot. Ankle sprains occur with inversion and plantar flexion mechanisms, like most of the fifth metatarsal basis fractures. Our aim was to investigate the possible accompanying ankle injuries about the fifth metatarsal basis fractures.Methods: Hospital's digital database was searched for the ICD 10 codes of the metatarsal bone fractures such as 'S92.30 and S92.35' between January 2015 and January 2018. Thirty nine patients with fifth metatarsal basis fracture who had an ankle magnetic resonance imaging (MRI) within 14 days of the injury were included in the study. MRI findings were evaluated and comparison was performed according to the fracture zones, gender and age.Results: The most common finding on MRI was talocrural joint effusion (TTJE) which was observed in 28 patients (71.8%). Bone marrow edema was observed in 16 patients (41%). Chondral injury at the medial dome of talus was observed in three patients (7.7%). Grade 1 ligament sprain was observed in 6 of the patients (15.4%). Lateral ligament sprain was observed only in two patients, while four of the sprains were about the deltoid ligament.Conclusions: Although most of the fifth metatarsal basis fractures and ankle sprains occur as a result of a common mechanism, physical examination and patients' complaints are very important. Routine MRI imaging should be unnecessary for most patients. If a patient with a fifth metatarsal basis fracture has complaints about his/her ankle joint, one should be aware of bone marrow edema which was observed in 41% of our study population.

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