1 sentence

1. 膝盖骨位于膝关节的前方，起到了保护关节的作用。

   xī​gài​gǔ wèi​yú xī guān​jié de qián​fāng, qǐ​dào le bǎo​hù guān​jié de zuò​yòng.

   The kneecap is located at the front of the knee joint and serves to protect it.

   Source: Dong Chinese Dictionary