flexion
noun [ U ] medical specialized uk/ˈflek.ʃən/ us/ˈflek.ʃən/
活动（手臂、腿等）;绷紧（肌肉）
the act of bending an arm, leg, etc. or of tightening a muscle
After physiotherapy, the shoulder flexion significantly increased. 物理治疗以后，肩膀的活动能力显著提高。
hip flexion 髋关节屈曲