His arm looks like a broken compass;it's not an arm any more, but a knucklebone with a shank attached.
他胳膊活像一只破损南针,早已一条胳膊,却成加上一条胫骨节。
The most common type of joint in the human body is the diarthrodial joint -- knuckles and shoulders are examples -- in which two bones come together in a capsule.