Fluid distribution in ankle and midfoot joints

PURPOSE: The purpose of this study is to assess the amount of fluid in the joints of the ankle and midfoot on MR imaging in asymptomatic volunteers.

MATERIALS AND METHODS: Twenty-one healthy asymptomatic volunteers (42 ankles) were evaluated with MRI imaging. There were 13 men and 8 women. The mean age was 24.7 years (19-42 years). MR imaging was performed on a 3T MR system using proton density weighted images with fat saturation (TR 2969, TE 30 ms, NA 2, slice thickness 2.5 mm). Images were obtained in three orthogonal planes. The images were interpreted by two radiologists in two sessions. The maximum size of the joint effusion was measured in one plane. Descriptive statistics and variation between interpretation sessions were calculated.

RESULTS: Fluid in the anterior tibiotalar joint had a mean size of 2.0 mm (0.0-5.5 mm), in the posterior tibiotalar joint 3.1 mm (0.0-6.3 mm), in the talonavicular joint 0.7 mm (0.0-2.9 mm), and in the anterolateral recess 2.0 mm (0.0-4.3 mm). Fluid in the posterior aspect of the posterior subtalar joint had a mean size of 2.6 mm (0.0-9.4 mm), in the anterior aspect of the posterior subtalar joint 1.9 mm (0.0-6.6 mm), at the middle subtalar joint 0.1 mm (0.0-1.7 mm), and at the anterior subtalar joint 1.6 mm (0.0-6.0 mm). Fluid in the tibiofibular joint had a mean height of 8.1 mm (0.0-16.4 mm).

CONCLUSION: In asymptomatic volunteers, moderate to large amounts of fluid were common in all joint recesses of ankle and midfoot, and most pronounced in the anterior and posterior tibiotalar joint, anterolateral recess, and posterior subtalar joint. This should not be mistaken for evidence of a pathological condition.