but the main thing that lubricates

但起到主要润滑作用的物质是
it is protective layer of cartilage

保护性软骨层
or soft skeletal material.

或者说软骨材料
Not bone but a soft spongy material

并非骨质而是软海绵状的材料
that lubricates between bones,

在骨骼间起润滑作用
and that can break down in diseases like arthritis.

关节炎之类的疾病可以损坏它
Well, this is what an artificial hip looks like.

这就是人造髋关节的外观
The modern hip is composed of two parts,

现代髋关节由两部分组成
there's a cup which goes into your pelvis

其中伸进骨盆的杯状结构
that replaces the normal structures into which the femur goes.

取代了有股骨插入到其中的正常结构
So, it replaces the cartilage

就是取代了软骨和
and the bony structure around the pelvis,

骨盆周围的骨质结构