Hi wstdst1,
No published studies have been conducted on this matter, but there appears to be nothing about the nature of a fully successful TKR that would meaningfully increase the risk of DCI in recreational SCUBA.
There should be no significant swelling, redness, looseness or pain in or around the joint even after moderate use, and the orthopedic surgeon should have released the patient for full physical activity, including diving. If DAN does so as well, that's icing on the cake.
The diver with TKR will want to be cautious not to fall or twist the knee while on deck or performing shore entries/exits. Whenever possible, don and doff gear in the water. Climbing a boat ladder or steep incline after a dive with gear still on definitely should be avoided. Also, it would be wise to avoid any other strenuous activity involving the knee for several hours before and after a dive.
Of course, even for the diver without a prosthesis, shorter, shallower dives; longer safety stops and surface intervals; deep stops where indicated; and using nitrox if so certified, are prudent.
Helpful?
Regards,
DocVikingo