MRI findings of tibialis anterior friction syndrome: a mimic of tibial stress injury.

objectiveTo describe a distinct constellation of MRI demonstrated soft tissue abnormalities centred around the tibialis anterior tendon in a subset of patients presenting as suspected tibial stress injury. MATERIALS AND

methodsA retrospective review was performed of the clinical and MRI imaging findings from 5 selected patients referred for MRI with suspected tibial stress injury. MRI studies at presentation of each case were systematically reviewed for peritendinous fluid, tibialis anterior tendon change, tibialis anterior muscle and myotendinous junction oedema, periosteal oedema over the tibia and tibial marrow oedema.

resultsAll 5 cases were athletes (3 soccer players, 2 runners) of between 20 and 40 years of age. On MRI, all 5 cases demonstrated peritendinous fluid around an intact tibialis anterior tendon. This fluid was maximal at the junction of mid and distal thirds of the lower leg, and extended down to the superior extensor retinaculum, with a mean cranio-caudal length of 13 cm (range 8-17 cm). Associated oedema was present in the surrounding subcutaneous tissue, tibial periosteum and distal tibialis anterior musculotendinous junction.

conclusionPeritendinous fluid around an intact tibialis anterior tendon over the mid-to-distal third tibia, with surrounding subcutaneous, periosteal and tibialis anterior myotendinous junction oedema is demonstrable on MRI in a subset of patients presenting as suspected tibial stress injury. A friction syndrome of tibialis anterior between the superior extensor retinaculum and the anterior tibia is proposed as the aetiology of this entity.