Predicting individual knee range of motion, knee pain, and walking limitation outcomes following total knee arthroplasty

Abstract

Background and purpose — Up to 20% of patients are dissatisfied after total knee arthroplasty (TKA), mainly because of pain and restricted physical function. We developed a prediction model for 6-month knee range of motion, knee pain, and walking limitations in patients undergoing TKA surgery. Patients and methods — We performed a prospective cohort study of 4,026 patients who underwent elective, primary TKA between July 2013 and July 2017. Candidate predictors included demographic, clinical, psychosocial, and preoperative outcome measures. The outcomes of interest were (i) knee extension and flexion range of motion, (ii) knee pain rated on a 5-point ordinal scale, and (iii) self-reported maximum walk time at 6 months post TKA. For each outcome, we fitted a multivariable proportional odds regression model with bootstrap internal validation. Results — At 6 months post TKA, around 5% to 20% of patients had a flexion contracture ³ 10°, range of motion < 90°, moderate to severe knee pain, or a maximum walk time £ 15 minutes. The model c-indices (the probabilities to correctly discriminate between 2 patients with different levels of follow-up TKA outcomes) when evaluating these patients were 0.71, 0.79, 0.65, and 0.76, respectively. Each postoperative outcome was strongly influenced by the same outcome measure obtained preoperatively (all p-values < 0.001). Additional statistically significant predictors were age, sex, race, education level, diabetes mellitus, preoperative use of gait aids, contralateral knee pain, and psychological distress (all p-values < 0.001). Interpretation — We have developed models to predict, for individual patients, their likely post-TKA levels of knee extension and flexion range of motion, knee pain, and walking limitations. After external validation, they can potentially be used preoperatively to identify at-risk patients and to help patients set more realistic expectations about surgical outcomes.

Does contralateral knee range of motion predict postoperative knee range of motion after total knee arthroplasty?

“…As mentioned, preoperative ROM in the operative knee is well established as the best predictor of postoperative ROM after TKA [1, 2, 4, 8-10, 12, 19-22, 27]. In two recently developed clinical predictive models by Pua et al [9] and Stratford et al [7], preoperative ROM and scores are primarily used to predict postoperative knee measures, with little if any weight in their models placed on other statistically significant factors such as patient sex, age, body mass index, underlying disease, preoperative walking limitations and pain.…”

“…The literature on preoperative risk factors and predictors for post-TKA flexion contracture and need for MUA mirrors that of predictors for post-TKA ROM, with the strongest and most reliable predictor being the presence of a preoperative flexion contracture in the operative knee, not readily varied by other factors [1,2,9,16,19,21,28,29]. Harato et al [25,26] have conducted gait and weight bearing studies in patients with flexion contractures and have delineated the abnormal forces placed on the contralateral knee in TK A [26] and non-TKA settings [25].…”

“…An important goal of total knee arthroplasty (TKA) is to achieve satisfactory postoperative range of motion (ROM) for the patient, as ROM is an important outcome measure of TKA [1][2][3][4] and is the main component of most knee scoring systems [5,6]. Several studies have sought to determine predictive factors of postoperative ROM after TKA, and this is an area of active research [4,[7][8][9].…”

“…Similarly, implant design and insert type have not been shown to affect postoperative ROM [11][12][13][14][15][16]. Several other studies have evaluated a variety of demographic and comorbidity-related factors that have shown to have some but variable predictive value [4,8,9,17,18].…”

“…To date, the factor that has consistently been shown in the literature and is well established to predict postoperative ROM is preoperative ROM in the same knee [4,8,9,[19][20][21]. Preoperative flexion has consistently been shown to be the strongest predictor of postoperative flexion [1,2,4,10,12,22].…”