There is a deep seated ball (femoral head) which fits tightly into a well-formed socket (acetabulum) with minimal joint space.

股骨头很深地被包覆于构造良好的关节窝里，且股骨头与关节窝之间的接缝空隙非常小。

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The inner side surface of the ball sleeve is contained outside the joint head in an insulating way to form a cardan joint.

球套内侧面吻合包含于关 节球面之外，形成万向节。

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