Proximal gastrocnemius and superficial digital flexor (SDF) muscle injuries are reported in the horse but are uncommon. In adult horses, the definitive diagnosis is more commonly based on clinical signs with or without the use of radiographic examination and/or nuclear scintigraphy. This case report describes the clinical and ultrasonographic findings of a tear of the gastrocnemius muscle in a 6-year-old reining mare. At standing physical examination, there was a sickled hock appearance, with the point of the hock of the left hindlimb lower (dropped hock) than that of the right hindlimb. At dynamic examination at walk, the mare had instability of the left hock characterised by medial rotation of the hoof and lateral rotation of the point of the hock (twisting motion); at trot, the horse showed mild/moderate left hindlimb lameness characterised by more downward movement of the pelvis during weightbearing of the lame limb compared with that of the sound limb. Ultrasonographic examination of the left thigh and crus showed a large irregular hypoechogenic area and irregularly shaped, retracted muscle stumps on the lateral aspect of the gastrocnemius muscles; the proximal insertion of the SDF muscle on the supracondylar fossa of the femur was irregular in its outline, hypoechogenic and thickened compared with that of the right side. Characteristic muscle fibre pattern was not identified in the left gastrocnemius muscle. On the radiography, a mild irregularity of the bone margin of the lateral supracondylar tuberosity was detected on the caudo 45° medial-craniolateral oblique view of the distal femur. Clinical and diagnostic imaging findings were consistent with partial failure of the caudal part of the reciprocal apparatus and injury of the gastrocnemius and SDF muscles/origin. The horse was managed conservatively by corrective shoeing, muscle relaxing drugs, controlled exercise and manual stretching.

中文翻译：

---

一匹被勒紧的 Quarter Horse 母马腓肠肌撕裂和浅表屈肌起源的附着点病变的临床和超声检查结果

据报道，马的近端腓肠肌和浅表屈肌 (SDF) 肌肉损伤并不常见。在成年马中，确诊更常见的是基于临床症状，使用或不使用放射学检查和/或核显像。本病例报告描述了一匹 6 岁的驯马母马腓肠肌撕裂的临床和超声检查结果。站立体格查体呈镰状飞节，左后肢飞节尖（飞节下垂）低于右后肢飞节。在行走动态检查中，母马左飞节不稳定，其特征是蹄向内侧旋转和飞节点向外侧旋转（扭转运动）；在小跑时，这匹马表现出轻度/中度左后肢跛行，其特征是与健全肢体相比，跛足在负重期间骨盆更多地向下移动。左大腿和小腿的超声检查显示腓肠肌外侧有一个大的不规则低回声区和形状不规则、收缩的肌肉残端；SDF肌在股骨髁上窝的近端插入轮廓不规则，与右侧相比，回声低且增厚。在左侧腓肠肌中未发现特征性肌纤维模式。在 X 光片上，在股骨远端的尾端 45° 内侧 - 颅外侧斜视图上检测到外侧髁上结节的骨缘轻度不规则。临床和诊断影像学发现与相互器官的尾部部分衰竭以及腓肠肌和 SDF 肌肉/起源的损伤一致。这匹马通过矫正鞋履、肌肉松弛药物、控制运动和手动拉伸进行保守管理。