Reliability of heel-height measurement for documenting knee extension deficits.

Background: Heel-height difference has been used to detect subtle knee flexion contractures, but the effects of thigh circumference differences and patient positioning during testing have not been evaluated.

Hypothesis: Differences in thigh circumference measurements and whether the patient's patellae are on or off the examination table during heel-height difference measurement will not affect the accuracy of detecting knee flexion contracture.

Study Design: Prospective cohort study.

Methods: Bilateral knee range of motion, prone heel-height difference with the patellae on and off the table, and thigh circumference at 5 and 15 cm proximal to the proximal pole of the patella were measured by one investigator on 50 consecutive patients who had undergone unilateral anterior cruciate ligament reconstruction.

Results: A high degree of correlation was demonstrated between the heel-height difference and the standard range of motion measurement. Differences in thigh girth and patellar position did not statistically affect the accuracy of the heel-height difference as an indicator of knee flexion contracture.

Conclusion: Heel-height difference is a valid method of documenting knee flexion contractures. Compared with traditional goniometer assessment, this test is a more meaningful and easier way for detecting subtle knee flexion contractures of less than 10 degrees.