He felt some discomfort in his popliteal area after running.

popliteal 是形容词，由名词 poples（拉丁语，意为"膝盖后部"）加上形容词后缀 -al 构成，指"与膝盖后部相关的"。 popliteal area 指膝盖后方的凹陷区域，即"腘窝"。