Ultrasonographic evaluation of the canine gracilis, semimembranosus, and semitendinosus muscles.

Standardized ultrasonographic scanning of caudal thigh muscles enables early diagnosis of fibrotic myopathy in dogs.

This tutorial article describes a standardized ultrasonographic technique for evaluating the gracilis, semimembranosus, and semitendinosus muscles in dogs, using two clinically healthy German Shepherd Dogs as subjects. Dogs were sedated and positioned in dorsal recumbency with bilateral coxofemoral abduction to facilitate access to the medial and caudal thigh musculature. A high-frequency linear transducer was employed, with image optimization achieved through adjustment of depth, focal zone, gain, and time-gain compensation. Scanning was performed in both transverse and longitudinal planes to assess muscle origin, body, and insertion points. In the transverse plane, the gracilis was identified as a superficial, flat adductor muscle; the semimembranosus was located deeper; and the semitendinosus was positioned more caudally with a distinctive rounded contour. Normal anatomic relationships, echogenicity patterns, and fiber orientations were documented to establish reference standards for consistent evaluation. The authors emphasize that familiarity with normal sonoanatomy is critical for identifying pathological changes, particularly fibrotic myopathy—a condition commonly affecting these muscles in German Shepherd Dogs and other breeds. Ultrasonography offers advantages including real-time dynamic assessment, absence of ionizing radiation, accessibility, and relatively low cost compared to advanced imaging modalities. This standardized approach provides a reproducible framework for clinicians to detect early muscle pathology, potentially enabling timely intervention and improved patient outcomes. The study received IACUC approval and owner consent prior to enrollment.

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