The introduction of biologic disease-modifying anti-rheumatic drugs (DMARDs) has been associated with a decrease in total knee replacements among rheumatoid arthritis patients. That’s according to a Danish study of some 30,500 RA patients, matched with nearly 298,000 controls, which appears in Annals of the Rheumatic Diseases.

In 1996, Danish rheumatoid arthritis patients had incident rates of total hip and total knee replacement of 8.72 and 5.87 respectively. Among the general public, the rates were significantly lower: 2.89 for hip (3 times less) and 0.42 for knee (14 times less) replacements.

The story for the Danish rheumatoid arthritis patients since 1996 has been a tale of two arcs. For total hip replacements, the incidence rate decreased over that time period for RA patients, while it increased for the general public.

RA patients saw an increase in total knee replacements from 1996 until 2001, but beginning in 2003, in what the study calls the “DMARD era,” the rate of total knee replacements for RA patients decreased. From 1996 to 2016, knee replacements increased for the general public.

“If treatment with bDMARD reduces the need for joint replacements, this will likely change the cost-effectiveness of these drugs,” wrote lead author René Lindholm Cordtz, of Copenhagen’s Rigshospitalet-Gentofte, and colleagues, as quoted in MedPage Today. “Joint replacements are expensive procedures and carry the risk of potential adverse events; and risk estimates for complications are increased in patients with RA.”