Knee Injury and Osteoarthritis Outcome Score Trajectories After Primary Total Knee Arthroplasty in United States Veterans

Introduction: The volume of total knee arthroplasty (TKA) procedures continues to increase, including among United States (US) veterans, but there is little data characterizing recovery using validated knee -related questionnaires.Methods: In this prospective cohort study, we sought to establish the feasibility of longitudinal characterization of recovery after TKA using the validated Knee Injury and Osteoarthritis Outcome Score (KOOS), specifically focusing on two of the KOOS subscales (pain and quality of life (QOL)). We solicited participants who agreed to fill out these knee-related questionnaires preoperatively and 3, 6, and 12 months after discharge following unilateral TKA within the Durham Veterans Affairs Health Care System. We examined rates of prospective completion of the KOOS and face validity of scores at each study time point. We transformed and reported scores on the 0-100 scale, with zero representing significant knee pain or poor QOL and 100 representing no knee pain or good QOL.Results: Of 200 US veterans presenting between May 2017 and 2018, 21 (10.5%) agreed to participate by filling out the KOOS questionnaire longitudinally from before surgery until one year after discharge. All 21 (100%) participants were male and completed the two KOOS subscale questions (pain and QOL) preoperatively. Of those, 16 (76.2%) also completed KOOS at 3 months, 16 (76.2%) at 6 months, and seven (33.3%) at 12 months. Compared to mean preoperative values (pain: 33.47 + 6.78, QOL: 11.91 + 4.99), the KOOS subscale scores had significantly improved by 6 months after TKA (pain: 74.41 + 10.72, QOL: 49.61 + 13.25) but plateaued at 12 months (pain: 74.60 + 20.80, QOL: 50.89 + 20.61). The magnitude of improvement in absolute scores, pain and QOL, was similar and significant at 12 months compared to preoperative values with an increase of 41.13 (p=0.007) and 38.98 (p=0.009), respectively. Conclusion: Primary TKA in US veterans with advanced osteoarthritis may lead to improved patient -reported KOOS pain and QOL subscale measures at 12 months compared to preoperative scores, with the majority of improvement occurring by 6 months. Only one in ten US veterans approached preoperatively agreed to complete the validated knee-related outcomes questionnaire prior to undergoing TKA. About three-quarters of those veterans also completed it both three and six months after discharge. Collected KOOS subscale scores demonstrated face validity and showed substantial improvement in pain and QOL over the six-month postoperative period. Only one in three veterans who completed the KOOS questionnaire preoperatively also completed it at 12 months, but this does not support the feasibility of follow-up assessments beyond 6 months. To better understand longitudinal pain and QOL trajectories in US veterans undergoing primary TKA for advanced osteoarthritis and to improve study participation, additional research using the KOOS questionnaire may add further insights into this underreported population.