The risk of subsequent joint arthroplasty after primary unilateral total knee arthroplasty, a 10-year study.

The purposes of this study were to determine the probabilities of subsequent lower extremity arthroplasty after index knee arthroplasty for osteoarthritis and to evaluate the demographic as well as radiographic factors that may predict progression to arthroplasty in the contralateral knee. Between 1984 and 1994, 646 patients, aged 40 to 75 years, with a primary cruciate-retaining knee were identified. The 10-year probability of having a contralateral knee after index knee was 36%. When grade 4 radiographic changes were present, the probability increased to 70%. Demographic factors played no role in the risk of future contralateral knee. The radiographic grade of the contralateral knee at the time of index surgery was found to correlate strongly with the future risk of contralateral total knee.