Width of the Retrocalcaneal Bursa Is Not Altered by the Ankle Motion or Flexor Hallucis Longus Contraction

The purpose of this study was to assess changes in the thickness of the retrocalcaneal bursa (RB) with respect to the ankle position with or without flexor hallucis longus (FHL) contraction. Forty feet of 20 female volunteers were examined. RB was sonographically scanned as the horizontal short-axis image of the posteromedial talar process and the calcaneal tuberosity. RB thickness was measured at three different ankle positions (20◦ dorsiflexion, neutral, and 40◦ plantar flexion) with or without FHL contraction. Without FHL contraction, the mean thickness of the RB was 2.6 mm in dorsiflexion, 2.4 mm in neutral, and 2.3 mm in plantar flexion. With FHL contraction, the mean thickness of the RB was 2.5 mm in dorsiflexion, 2.5 mm in neutral, and 2.3 mm in plantar flexion. No significant differences were detected with respect to the ankle position or FHL contraction. This study showed that in healthy subjects, the thickness of the RB in the horizontal plane did not change with respect to the ankle position with or without FHL contraction.