Maybe not! A recent study from Mayo Clinic reports good results for adults over age 90 getting their first total knee replacement (TKR). They also report on patients ages 90 to 102 who had a repair or replacement of a previous TKR.
Doctors are expecting to see more and more adults in their 90s (and older) outliving the TKR put in when they were in their 70s. Likewise, as more people live longer, first timers in need of a joint replacement may show up in their 90s.