Long-term prognosis of patellofemoral pain in adolescents and adults: A systematic review with meta-analysis and meta-regression.

ObjectiveTo investigate the long-term (defined as [&ge;]12 months) prognosis of knee pain and knee function in adults and adolescents with patellofemoral pain (PFP). DesignSystematic review with meta-analysis and meta-regressions. Data sourcesMEDLINE, OVID, CENTRAL, Web of Science, OpenGrey, and International Patellofemoral Research Retreat abstract books. Eligibility criteria for selecting studiesProspective studies of patients clinically diagnosed with PFP, aged <40 years, with a long-term follow-up (minimum of 12 months). Primary outcomes were self-reported pain intensity (worst, during activity, and usual) and function. Meta-analyses and meta-regressions were performed where appropriate. Narrative synthesis was performed for those not included in the metanalysis. Risk of bias was assessed using the Quality In Prognosis Studies (QUIPS) tool, and certainty of evidence using GRADE. ResultsA total of 42 studies (n = 3,230) were included. At 12 months, meta-analysis indicated reduction in worst pain (SMD 1.36; 95% CI 0.85-1.86), pain during activity (SMD 1.36; 95% CI 0.61-2.11), and resting pain (SMD 0.91; 95% CI: 0.75- 1.08). No significant reduction was found for usual pain. We found improvement in self-reported function (investigated using the Anterior Knee Pain Scale (AKPS) MD 14.60; 95% CI 11.60-17.61), FIQ (MD 3.33; 95% CI: 2.46- 4.20) and the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) (MD -7.73; 95% CI: -10.36 to - 5.10). Extended follow-up ([&ge;]60 months) suggested more variable improvements. Meta-regression showed no association between age and 12-month function, while older age was modestly associated with greater improvement in activity-related pain at extended follow-up. Overall, a considerable proportion of participants continued to report persistent symptoms, and heterogeneity across studies was substantial. Certainty of evidence ranged from very low to moderate across outcomes investigated. ConclusionPain and self-reported function generally improve over time, particularly within the first 12 months. However, substantial heterogeneity and persistent symptoms in a considerable proportion of patients at extended follow-up indicate that recovery is not universal and trajectories are highly variable. What is already knownO_LIPatellofemoral Pain (PFP) is a very common condition in both adolescents and adults. C_LIO_LIMultiple treatments modalities exist, including patient education and exercise therapy. C_LIO_LIPeople suffering from PFP request more knowledge on the long-term prognosis. C_LI What are the new findings?O_LIThis systematic review and meta-analysis provide the most comprehensive synthesis to date of long-term outcomes ([&ge;]12 months) in adolescents and adults with patellofemoral pain. C_LIO_LIPain and self-reported knee function generally improve at the group level over time, particularly within the first 12 months. C_LIO_LIDespite group-level improvement, a substantial proportion of individuals continue to report persistent symptoms, indicating that patellofemoral pain is often not fully self-limiting. C_LIO_LILong-term outcomes are highly heterogeneous, with different pain constructs demonstrating distinct trajectories across follow-up periods. C_LIO_LIMeta-regression identified no consistent prognostic associations, suggesting that current study-level variables explain little of the variability in long-term outcomes. C_LI How might this study affect research, practice or policy?O_LIClinicians should communicate that while improvement is common in patellofemoral pain, persistent symptoms are frequent, highlighting the need for realistic prognostic expectations and long-term management strategies. C_LIO_LIFuture research should prioritise harmonised outcome measures and long-term follow-up to better understand recovery trajectories and identify subgroups at risk of persistent symptoms. C_LI