Got a brand new metal knee.
Its only half a knee (called an Oxford) and is much harder to "install".
They opened me up, clamped a jig to upper and lower halves then routed out a notch.
Then used a 90 degree drill guided by a different jig to bore a hole straight up the middle of the notched out half.
Then bonded (glued) the the top and bottom halves.
Surgeons are like tool and die makers sometimes.
check it outhttp://www.biomet.com/patients/oxfordAnimationVideoPopup.cfm