Background Sixty to 80% of the patients with knee osteoarthritis (OA) reported self-reported knee joint instability, which was associated with pain and activity limitations. One previous randomized control trial described the prevalence of retained self-reported knee joint instability after total knee arthroplasty (TKA) (32%). To better understand self-reported knee joint instability in usual care there is a need to replicate and extend the results.
Objectives The aims of the study were to determine (i) the prevalence of self-reported knee instability prior and one year after TKA, (ii) the associations between self-reported knee instability, pain, activity limitations and quality of life prior and one year after TKA, (iii) the course of self-reported knee instability over time and (iv) the associations between retained knee instability, pain, activity limitations and quality of life.
Methods Consecutive patients with knee OA undergoing primary TKA, extracted from the Longitudinal Leiden Orthopaedics and Outcomes of OsteoArthritis Study (LOAS Study), were included. Self-reported knee joint instability and the Knee injury and Osteoarthritis Outcome Score (KOOS) Pain, Activity Daily Living (ADL) and QoL subscales (0–100; worst-best) were assessed by questionnaires prior and one year after surgery. Multivariable regression analyses were performed to determine associations between knee joint instability, pain, activity limitations and quality of life, adjusted for potential confounders including age, sex, comorbidities, physical activity and preoperative frailty.
Results 908 patients were included of which 649 patients (72%) reported preoperative knee joint instability (mean age 67 years (SD8.6), 453 females (70%)) and 187 patients (21%) postoperative knee joint instability. Preoperative knee joint instability was associated with preoperative KOOS Pain (B-7.2;95% CI-10.9–3.5) and ADL (B3.8;95% CI-7.5–0.09), but not QoL (B-0.4;95% CI-2.1–1.2). In addition, postoperative knee joint instability was associated with postoperative KOOS Pain (B-13.5;95% CI-17.0–10.0), ADL (B-15.1,95% CI-18.4–11.8) and QoL (B-11.0;95% CI-13.5–8.5). Among the patients with preoperative self-reported knee joint instability, 165 patients (25%) retained knee instability and among the patients with no preoperative self-reported knee joint instability, 22 (8%) developed knee instability one year after surgery. After adjusting for baseline scores and potential confounders, retained knee joint instability was associated with postoperative KOOS Pain (B-19.6;95% CI-30.9–8.3), ADL (B-16.5;95% CI-27.0–5.9) and QoL (B-13.0;95% CI-17.9–8.1).
Conclusions In usual care, knee joint instability is prevalent one year after TKA (21%). Reported knee joint instability is associated with more pain, worse physical function (pre- and postoperatively) and worse Qol postoperatively. Besides, retained knee joint instability was associated with worse pain, physical function and QoL. This emphasizes the importance of further research into the genesis of pre- and postoperative knee joint instability.
Acknowledgements The study was funded by the Dutch Arthritis Foundation (DAF).
Disclosure of Interest None declared