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.

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Objective. Quadriceps strength deficits and gait speed limitations remain significant issues after total knee arthroplasty (TKA), yet detailed longitudinal data characterizing these measures and their predictors are limited. This study aimed to describe the time course of knee range of motion, quadriceps strength, and gait speed post-TKA, and to assess whether sex and body mass index (BMI) influenced the time recovery of these measures. Methods. A total of 1,025 patients (mean 6 SD age 67 6 8 years) undergoing primary TKA participated. At 4-, 8-, 12-, and 16-weeks postsurgery, knee range of motion, quadriceps strength, and gait speed were quantified. The associations of the knee and gait measures profile over time with sex and BMI were assessed using generalized least squares modeling. Results. The various knee and gait measures improved nonlinearly over time, with substantial improvements observed in the first 8-10 weeks postsurgery. Sex and BMI influenced the time course of quadriceps strength (P < 0.001 for all interactions): improvements in quadriceps strength over time were slower in women and in patients with higher BMI. Post-TKA gait speed was consistently lower in women than in men, while BMI was negatively and nonlinearly related to gait speed. Conclusion. Although the various knee and gait measures improved over time, women and patients with higher BMI had poorer functional outcomes. The present study highlights the need for a mechanistic understanding of the results and targeted management of these patient subgroups.

Rehabilitation attendance post-TKA is associated with an increase in self-report physical function. Among patients who attended rehabilitation, a modest dose-response relationship was observed between the number of sessions and functional outcomes.

A small but sizable proportion of patients with TKA had persistent mobility limitations. Our prediction model may help to risk-stratify patients, and external validation is required before the model can be used in clinical practice.