Reliability of musculoskeletal ultrasonography for peri-ankle muscles in subjects with unilateral chronic ankle instability.

Background: Ankle sprain is a common problem among active people and athletes. It causes reduces their activity of daily living and quality of life. Because of the impaired muscle strength and neuromuscular and postural control, it seems that the morphological criteria of peri-ankle muscles are changed.

Objective: This study aimed to develop a reliable method for measuring tibialis anterior (TA) and peroneus longus (PL) muscles in the injured and intact side of lower limbs in people with unilateral chronic ankle instability (CAI).

Study Design: Cross-sectional study.

Method: This study was intra-tester reliability by ultrasound imaging to measure ultrasonography characteristics contains thickness, width, fiber length, pennation angle, and cross-sectional area (CSA) of TA, and PL in both limbs of 25 subjects at three separate times. Intra-class correlation coefficients (ICC), limits of agreement (LOA), standard error of measurement (SEM), and minimal detectable change (MDC) were calculated to analyzed relative and absolute intra-tester reliability, respectively.

Results: The present study showed good to excellent relative reliability for both injured and intact sides (ICC 0.88-0.98), less proportional measurement error (β coefficient of LOA≈ 0), and suitable absolute reliability.

Conclusion: Musculoskeletal ultrasonography is a reliable method for the measurement of peri-ankle muscle morphology such as thickness, width, CSA, fiber length, and pennation angle.