It affected the young animal's front legs, which became hyperextended.

这种疾病影响了幼崽的前肢，使前肢腕关节过度伸展。

These muscles include the flexor digitorum profundus which flexes the fingers at the interphalangeal joints, and the extensor digitorum which hyperextend them at the metacarpal phalangeal joint.

前臂肌群包括指深屈肌（在指间关节处使手指屈曲）及指伸肌（在掌指关节处使手指过伸）。