The Recovery Curve for the Patient-Reported Outcomes Measurement Information System Patient-Reported Physical Function and Pain Interference Computerized Adaptive Tests After Primary Total Knee Arthroplasty.

BACKGROUND: We sought to characterize the typical recovery in physical function (PF) and pain interference (PI) after TKA using Patient-Reported Outcomes Measurement Information System (PROMIS) patient-reported outcome (PRO) measures.
METHODS: Ninety-one patients were enrolled into an institutional review board -approved prospective observational study. PROs were obtained preoperatively and postoperatively at 6 weeks, 3 months, 6 months, and 1 year. PROs included the PROMIS PF computerized adaptive test (CAT) and the PROMIS PI CAT. Generalized estimating equations were used to evaluate outcomes over time.
RESULTS: There was no difference in the preoperative and 6-week postoperative T-scores for the PF CAT (P = .410). However, all subsequent postoperative T-scores were greater than the preoperative T-score (all, P < 0.05). There was a significant reduction in PI CAT T-scores between the preoperative and all subsequent postoperative T-scores (all, P < .05). A clinically important difference in PF CAT T-scores (β = 5.44, 95% confidence interval 4.10-6.80; P < .001) and PI CAT T-scores (β = -7.46, 95% confidence interval -9.52 to -5.40; P < 0.001) was seen between the preoperative and 3-month postoperative visits. Sixty-three percent of the improvement in PF occurred by 3 months, and 89% had occurred by 6 months. The majority of reduction in PI (68%) occurred by 3 months and 90% had occurred by 6 months.
CONCLUSION: The greatest magnitude of improvement in both PF and PI occurred within the first 3 months. After 6 months, patients might expect modest improvements in PF and mild reductions of PI. Patients and surgeons should use this information for setting expectations, planning for recovery, and improving care.