He was forced to withdraw from the tournament due to a strain in his shoulder.

strain 是名词，来自动词 strain（拉紧、过度使用），指肌肉或肌腱因过度拉伸或用力而造成的损伤，即"拉伤"。在医学上特指肌肉或韧带的轻微撕裂伤。