What Causes Post-Op Stiff Knee? Surprising Answer.

There are a lot of moving parts in the postoperative arena…and researchers from Hospital for Special Surgery (HSS) wanted to get a handle on one, namely, do anticoagulants affect stiffness after total knee arthroplasty (TKA)?

The resulting study, “Type of Anticoagulant Used After Total Knee Arthroplasty Affects the Rate of Knee Manipulation for Postoperative Stiffness,” appears in the August 15, 2018 edition of The Journal of Bone and Joint Surgery.

Co-author Cynthia Kahlenberg, M.D., orthopedic surgery resident at HSS, explained the study to OTW, “Stiffness continues to be a problem for a proportion of patients undergoing TKA. Although we already know that stiffness after TKA is multifactorial, we thought that there may be an effect of anticoagulant choice on stiffness.”

“We were aware of one prior study that specifically looked at stiffness among patients receiving warfarin versus low molecular weight heparin and found a higher rate of MUA [manipulation under anesthesia] in the warfarin group, but we wanted to delve deeper and take a look at this phenomenon on a larger scale and with more of the commonly used anticoagulants.”

The authors wrote, “Using the PearlDiver patient database, we analyzed 32,320 patients who underwent a primary unilateral total knee replacement from 2007 to 2015. Patients were included if they filled a prescription for anticoagulation medication within 2 days of their discharge and were excluded if they were taking a prescription anticoagulation medication (except for aspirin) in the 3 months before total knee replacement. The primary outcome was manipulation under anesthesia performed within 6 months after a primary total knee replacement.”

Dr. Kahlenberg told OTW, “We found that patients who received warfarin, direct Xa inhibitors, or fondaparinux after TKA were at significantly higher risk of undergoing manipulation under anesthesia for postoperative knee stiffness in comparison to patients who received low molecular weight heparin. In addition, there was no significantly increased risk of MUA in patients who received aspirin postoperatively.”

“We know that many factors go into the decision of which anticoagulant to give patients after surgery. While we certainly aren’t encouraging arthroplasty surgeons to base their anticoagulation decisions solely on the potential for postoperative stiffness, we do encourage surgeons to consider this effect of the oral anticoagulants including warfarin, direct Xa inhibitors, and fondaparinux when making their decisions on anticoagulation choice after TKA.”