Reliability of Achilles Tendon Resting Angle and Calf Circumference Measurement Techniques

Background: The resting angle of the ankle joint may be altered following apparently successful management of Achilles tendon rupture. The reliability of the Achilles Tendon Resting Angle and Calf Circumference measurements was determined.

Methods: Three test-retest measurements for reliability assessment were performed on 16 healthy subjects: 10 males and 6 females.

Results: The mean left Achilles Tendon Resting Angle was mean 50.1° (range [26-61]), ICC 0.92 (CI [0.83-0.97]), SEM 2.4°. The mean right Achilles tendon resting angle was mean 49.9° (range [26-60]), ICC 0.91 (CI [0.80-0.96]), SEM 2.6°. The mean left calf circumference was mean 38.5cm (range [33.3-44.2]), ICC 0.97 (CI [0.94-0.98]), SEM 0.6cm, and the mean right calf circumference was mean 38.4cm (range [33.3-43.6]), ICC 0.97 (CI [0.94-0.99]), SEM 0.5cm.

Conclusions: The Achilles Tendon Resting Angle and Calf Circumference at 15cm from the antero-medial joint line had excellent test-retest reliability. These are simple, quick and inexpensive measurements, which have the potential to correlate with tendon elongation and functional outcome. The Achilles tendon resting angle may be used as a guide to tendon length during intra-operative repair and rehabilitation.