Abstract
INTRODUCTION: Mucoid degeneration of the anterior cruciate ligament (ACL) is a very rare cause of knee pain. Patient having mucoid degeneration of ACL seeks multiple orthopedic consultation and most of the time treating orthopedican miss its diagnosis either because of lack of experience or rare cause of pain unless doctor sought magnetic resonance imaging (MRI) of knee. CASE REPORT: We report a case of mucoid degeneration of the ACL in a 50-year-old female with knee pain of 18 months duration. The patient presented with extension block of the knee. After arthroscopic debridement of the lesion, the patient regained full range of motion of the knee and were pain-free at follow-up. CONCLUSION: A long duration of non-specific knee pain in a patient should be evaluated with MRI. Mucoid degeneration of the ACL is suspected when an apparently thickened and ill-defined ligament with increased signal intensity on all sequences in MRI is identified in a patient with physically intact ligament and no obvious trauma history. Arthroscopic debridement of the mucoid degeneration of the ACL was safe and effective in the patient.