Are modern knee outcomes scores appropriate for evaluating anterior knee pain and symptoms after total knee arthroplasty?

BACKGROUND: Up to 45% of patients who undergo primary total knee arthroplasty (TKA) with contemporary implants have residual anterior knee pain. While a specific evaluation of anterior knee symptoms is mandatory, little is known about the capability of patellofemoral scores to be used individually. This study aimed to assess the distribution of patellofemoral scores after TKA from a uniform cohort and to investigate their external validity and ability to detect anterior knee symptoms using floor and ceiling effects. HYPOTHESIS: Patellofemoral scores have high construct validity and fewer floor/ceiling effects than general knee scores. METHODS: We prospectively included 113 consecutive patients who underwent primary TKA for primary osteoarthritis at a single University Hospital. Clinical outcomes included patellofemoral scores (HSS Patella, Kujala and Lille scores) and general knee scores (KOOS and new KSS) at 1-year follow-up. The floor and ceiling effects were considered as significant when greater than 15%. These were determined for each score individually and for composite scores (combination of patellofemoral scores and new KSS). The construct validity of each score and their ability to detect anterior knee pain was evaluated. RESULTS: Patellofemoral scores showed no floor effect but a significant ceiling effect (from 25% to 65%). This ceiling effect decreased when composite scores were used. The convergent validity test showed strong correlation between patellofemoral scores (from 0.741 to 0.819, p<0.00001) and a better ability to discriminate anterior knee pain than the general knee scores. CONCLUSIONS: Patellofemoral scores showed no floor effect and a very good construct validity for anterior knee pain after TKA. However, studies aiming to monitor anterior knee symptoms after TKA should combine scoring systems to included patellofemoral-related items rather than use patellofemoral scores alone due their ceiling effects. LEVEL OF EVIDENCE: III; prospective study.

Influence of residual anterior laxity on functional outcomes after anterior cruciate ligament reconstruction.

INTRODUCTION: Residual laxity can persist after anterior cruciate ligament (ACL) reconstruction. This increased anterior translation can be measured with a knee arthrometer. Nevertheless, the measurement parameters and functional impact of this residual laxity are not well understood. The aims of this study were to (1) evaluate the effect of applying loads of 134N, 200N and 250N on the measured residual laxity after ACL reconstruction and (2) evaluate the prognostic ability of the various measurement parameters on the functional outcomes. HYPOTHESIS: After ACL reconstruction, the functional outcomes will be correlated to the postoperative residual laxity. METHODS: We did a prospective study of 61 recreational athletes who underwent surgical reconstruction of their ACL with the Kenneth-Jones technique between 2016 and 2019. The mean age of these patients was 27±7 years, and most were men (75%). The side-to-side difference in laxity was measured pre- and postoperatively using the GNRB® arthrometer at three load levels: 134N, 200N and 250N. The functional outcomes were determined based on the return to sports and the KOOS, IKDC and ARPEGE scores. The mean follow-up was 30±10 months. RESULTS: Half the patients had returned to sport at their pre-injury levels, while 25% had returned to a lower level and 25% had stopped doing any physical activity. At 134N, a 1-mm increase in side-to-side difference was associated with a 2-fold higher risk of not returning to sports (OR 2; 95% CI 1.22-3.23; p<0.01). At 200N, a 1-mm increase in side-to-side difference was associated with a 50% higher probability of having a poor/fair ARPEGE score (OR 1.5; 95% CI 1.05-2.02; p=0.02). At 200N, a 4-mm side-to-side difference was the prognostic threshold for failure to return to sports with a positive predictive value of 86% and specificity of 98%. CONCLUSIONS: This case series found a strong correlation between residual laxity and the functional outcomes after ACL reconstruction. A threshold of 4mm residual laxity evaluated on the GNRB® at 200N was predictive of adverse outcomes and failure to return to sports in our population of recreational athletes. LEVEL OF EVIDENCE: IV, retrospective study.