|Top of knee joint.
This is the top of an artificial knee joint: I've removed the plastic block that attaches just underneath this metal part, and which mates with the double-ball of the other half, which you can see under aluminum. Unfortunately they seem to be a different brand or something because the parts don't fit each other.
I originally thought these were titanium, but the source, Paul Wellin's Brother, reports as follows:
"The top of knee joint and the hip joint ball attachment are probably made of a different alloy, cobalt-chrome, for increased strength and decreased flexibility as compared to titanium."
I don't know whether there is more cobalt or more chromium in the alloy, so I've somewhat arbitrarily chosen to put them under cobalt.
Source: Paul Wellin
Contributor: Paul Wellin
Acquired: 14 June, 2002
Text Updated: 11 March, 2007
Sample Group: Body Parts+Medical