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

Objective: To describe a practical technique for ultrasonographic evaluation of the gracilis, semimembranosus, and semitendinosus muscles in dogs. Animals: 2 clinically healthy client-owned German Shepherd Dogs were used for this tutorial. Owner consent and approval from the University of Florida College of Veterinary Medicine IACUC were obtained prior to participation. Methods: Dogs were clipped, sedated, and placed into dorsal recumbency in a relaxed position with bilateral coxofemoral abduction. A stepwise ultrasonographic approach was demonstrated with a high-frequency linear transducer. The image was optimized by adjustment of depth, focal zone placement, gain, and time-gain compensation. Scanning was performed in both transverse and longitudinal planes to assess muscle origin, body, and insertion. Normal anatomic relationships of the gracilis, semimembranosus, and semitendinosus muscles were identified to facilitate consistent evaluation. Results: Ultrasound allowed clear identification of the gracilis, semimembranosus, and semitendinosus muscles on the basis of location, shape, echogenicity, and fiber orientation. The gracilis was identified in a transverse plane as a superficial, flat adductor muscle, with the semimembranosus located deeper and the semitendinosus positioned more caudally with a rounded contour. Standardized scanning planes enabled consistent visualization of muscle architecture and tendon attachments. Clinical Relevance: Ultrasonography is a valuable, accessible tool for evaluating the gracilis, semimembranosus, and semitendinosus muscles in dogs. Familiarity with normal anatomy and scanning techniques is essential for the diagnosis of conditions such as fibrotic myopathy, facilitating earlier intervention.