A large-scale review of nearly 600,000 total knee replacement cases found that about 20% of patients reported ongoing pain 3 months postsurgery. More than 12% continued to report pain 2 years later.

Investigators analyzed 68 studies on total knee replacement (TKR) and 11 on total hip replacement (THR) to estimate how many patients experienced long-term joint pain following surgery. Most patients underwent joint replacement as a result of severe osteoarthritis.

For TKR, the pooled prevalence of postoperative pain was:

• 21.9% at 3 months (95% credible interval [CrI] = 15.6%–29.4%)
• 14.1% at 6 months (95% CrI = 10.9%–17.9%)
• 12.6% at 12 months (95% CrI = 9.9%–15.9%)
• 14.6% at 24 months (95% CrI = 9.5%–22.4%)

For THR, limited data prevented trend analysis. Only one study reported pain at 3 and 24 months, making it impossible to establish a reliable trajectory. However, 13.8% of patients reported pain at 6 months (95% CrI = 8.5%–20.1%) and 13.7% at 12 months (95% CrI = 4.8%–31.0%).

“Approximately 22% of patients will report an unfavorable pain outcome at 3 months after TKR,” the study authors wrote. They defined unfavorable pain using study-specific criteria, including moderate to severe pain or inadequate relief postsurgery.

The team used Bayesian meta-analysis to synthesize findings across studies. Although the sample size was large, pain measurement methods varied. Some studies used standardized tools like the Visual Analogue Scale or the Western Ontario and McMaster Universities Osteoarthritis Index; others used study-specific questions.

Most included studies were assessed as having moderate risk of bias, with many losing more than 25% of participants to follow-up. When the investigators adjusted for missing data, estimates of persistent pain increased. Sensitivity analyses showed that assuming even a modest proportion of lost participants experienced pain could significantly raise prevalence estimates—suggesting that the true burden may be underestimated.

Differences in pain definitions, follow-up loss, and study populations contributed to variation in the findings. Despite this, the investigators reported that their results may offer a realistic estimate of long-term pain rates following joint replacement.

Chronic postsurgical pain can impair quality of life and increase health care utilization. Past studies have linked it to preexisting pain, mental health conditions, and surgical complications. Identifying patients at higher risk may support improved outcomes.

The investigators recommended more research into long-term recovery and strategies to manage pain following joint surgery. They also encouraged routine monitoring of postoperative pain beyond the early recovery period.

The review included studies published between 1993 and 2023, with most conducted in Europe and North America.

The authors reported no competing interests.

Source: BMJ Open