膝关节是人体最大的关节。 这是一个可以弯曲和伸展以及可以稍微旋转的关节。 它很容易受伤，很容易发展成关节炎。
The knee joint is the largest joint in the human body. This is a joint that can bend and stretch, as well as can rotate slightly. It is easily injured and can easily develop into arthritis.
