RESUMO
INTRODUCTION: Arthrofibrosis develops in 3-10% of knees after total knee arthroplasty (TKA), which may result in pain and restricted range-of-motion. Treatment options include manipulation under anaesthesia, arthroscopic debridement, and quadricepsplasty, but there is little consensus on their efficacy for treatment of unexplained pain after TKA. The purpose of this study was to report the prevalence and characteristics of unexplained pain after TKA as revealed by arthroscopic exploration, and assess the efficacy of arthroscopic procedures to relieve pain. MATERIALS AND METHODS: From a consecutive series of 684 TKAs, 11 patients (1.6%) had unexplained pain at 7-48 months after TKA. Causes of pain remained unidentified after systematic and differential assessment, but arthroscopic exploration revealed fibrotic tissues, which were debrided during the same procedure. Patients were assessed first at 6-61 months and last at 90-148 months, with pain on a visual analog scale (pVAS) and range-of-motion recorded during both assessments, but Oxford Knee Score (OKS) and Forgotten Joint Score (FJS) only during the last assessment. Residual pain was classified as little or no pain (pVAS, 0-1), moderate pain (pVAS, 2-4), and severe pain (pVAS, 5-10). RESULTS: At first follow-up (n = 11) pVAS improved by 4.1 ± 1.1 (p < 0.001), and range-of-motion improved by 5.0° ± 7.1° (p = 0.041). Seven patients (64%) had little or no residual pain, while four (36%) had moderate residual pain. At final follow-up (n = 9) pVAS improved by 3.2 ± 2.9 (p < 0.001), and range-of-motion improved by 4.4° ± 8.5° (p = 0.154). Six patients (67%) had little or no residual pain, while one (11%) had moderate and two (22%) had severe residual pain. CONCLUSION: Arthroscopic exploration revealed that all 11 knees with unexplained pain had fibrotic tissues, the removal of which alleviated pain in only 67%, while moderate to severe pain persisted in 33% which merits further scrutiny.