Purpose : Mucoid degeneration of the Anterior cruciate ligament(ACL) is not a well-known entity. Only 1 case of mucoid degeneration of the ACL has been reported in the English literature. This article describes 5 cases of mucoid degeneration of the ACL with clinical features, MRI findings and a method of arthroscopic management of these cases.

Methods : Over a period of 18 months from 1999-2001, 5 patients were diagnosed to be suffering from mucoid degeneration of the ACL using MRI, histopathological and arthroscopic criteria. All patients presented with progressive knee pain and restriction of flexion without history of a significant trauma or instability preceding the symptoms. MRI showed an increased signal in the substance of the ACL both in the T1 and T2 weighted images with a mass like configuration that were reported as a partial or complete tear of the ACL by most radiologists. At arthroscopy the ACL was homogenous, bulbous, hypertrophied and taut occupying the entire intercon-dylar notch. The ligamentum mucosum was absent in all patients. A debulking of the ACL was performed by a judicious excision of the degenerate mucoid tissue taking care to leave behind as much of the intact ACL as possible. Releasing it and performing a notchplasty treated impingement of the ACL to the roof and lateral wall. The ACL was not fully excised in any of the patients.

Results : All patients were pain free and had recovered full flexion except one who had painful flexion beyond 120°. None of the patients had symptoms of instability.

Conclusion : Mucoid degeneration of the ACL is a clinical condition afflicting active middle aged people without a single significant traumatic episode with a specific MRI picture. They respond well to a judicious arthroscopic release of the ACL with notchplasty.