杵臼关节也称为球窝关节，是一种滑液关节，是最灵活的关节，可移动骨头的末端成圆球状，刚好可以塞入固定骨头的臼窝中，骨头可以旋转及朝各个方向自由转动。

用髋关节为例，其中圆形的股骨头（球）置于像骨盆中像杯子一様的关节窝（窝）中，而肩的盂肱关节也是类似，球窝关节的「球」对应肱骨的头部，「窝」则对应肩胛骨中的肩臼。不过肩膀除了上述部位外，还有胸锁关节。

• 髋关节

• 肩

• 髋关节细部
  1.股骨
  2.股骨颈
  3.股骨头
  4.关节窝
  5. 髋臼唇（Acetabular Labrum）
  6.骨盆

In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles. They are used on virtually every automobile made and work similarly to the ball-and-socket design of the human hip joint.

A ball joint consists of a bearing stud and socket enclosed in a casing; all these parts are made of steel. The bearing stud is tapered and threaded, and fits into a tapered hole in the steering knuckle. A protective encasing prevents dirt from getting into the joint assembly. Usually, this is a rubber-like boot that allows movement and expansion of lubricant. Motion-control ball joints tend to be retained with an internal spring, which helps to prevent vibration problems in the linkage.