Early rehabilitation, return to daily life activities and function are the ultimate goals of perioperative care. It is unclear which pain-related patient-reported outcome measures (PROM) mirror treatment effects, or are related to early and late functional outcomes.

We examined associations between two approaches of pain management (scheduled vs. ‘on demand’) and PROMs on postoperative days one and five (POD1, 5) with function on POD5 and 3 months after surgery in patients undergoing total knee arthroplasty (TKA) in a single center.

On POD1, patients in the scheduled treatment group reported reduced severity of worst pain, less interference of pain with activities in-bed and sleep, and a higher proportion got out of bed. Furthermore, tests of function, extension and flexion ranges, Barthel index and 6minutes walking test on POD5, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) 3 months later were better in the scheduled treatment compared to the ‘on demand’ treatment group. PROMs of perceived pain relief at POD1 and worst pain, time in severe pain, interference with activities in bed and with sleep, and participation in treatment decisions on POD5 were significantly associated with KOOS 3 months later.

Our study demonstrates that insufficient pain management immediately after TKA has substantial impact not only on PROMs in the early days after surgery but also on important physical function up to 3 months later. Pain-related PROMs assessed at POD1 and especially at PO5 are associated with functional recovery up to 3 months.