Anisotropy is a major artifact in musculoskeletal ultrasound occurring when the ultrasound beam strikes a tendon or other fibrillar structure at an angle other than 90 degrees. The specular reflections from the tendon fibers are directed away from the transducer, causing the tendon to appear darker (hypoechoic) — mimicking tendinopathy or tearing. Anisotropy is identified and corrected by heeling and toeing the transducer (tilting it) to bring the beam perpendicular to the structure, restoring its normal bright fibrillar appearance.