He then tested how much friction there was when a ceramic ball and a polyethylene socket were immersed in a liquid with the same properties as synovial fluid.

BBC: Longer-lasting hip-joint hope

The Yankees immediately scheduled a more extensive dye-contrast MRI, which showed a significant tear of the labrum, the socket padding that holds the ball of the shoulder joint in place.

WSJ: Pineda Done Before Starting

It turned out that the handle had compressed the eyeball in and pushed it up in the socket (think about squeezing a rubber ball), but it remained attached.

CNN: Man's eye saved after impalement

Think of the labrum as a ring of soft tissue that holds the ball of the femur, or thighbone, snugly in the hip joint's socket.

CNN: Gaga's injury related to 'being active'