Loss of ankle movement is a complication of severe tibial fractures. This can be exacerbated if the foot is allowed to drop into equinus, particularly when an external fixator is employed. The range of ankle motion following external fixation of tibial fractures as compared to the opposite normal ankle was studied in 40 of 55 patients treated over a ten-year period. Nine were excluded due to other causes of ankle stiffness, leaving 31 cases for analysis. The mean follow up was 2 years 7 months (range 1 year to 8 years 3 months), and union had occurred by a mean of 35 weeks (range 9-100 weeks). The mean loss of ankle movement was 8 degrees of plantar-flexion and 12 degrees of dorsiflexion (overall loss 20 degrees), the difference between the two being highly significant (P greater than 0.001, t test). Loss of ankle motion closely paralleled the degree of soft tissue trauma, being 6 degrees for closed fractures and 22 degrees for open fractures (0.05 greater than P greater than 0.02). Ankle function is therefore at risk when a severe tibial fracture is treated by external fixation, and appropriate measures should be taken to preserve movement and prevent an equinus contracture.