Anterior cruciate ligament ganglia and mucoid degeneration: coexistence and clinical correlation.

OBJECTIVE: The purpose of our study was to describe the MR appearance and coexistence of anterior cruciate ligament ganglia with mucoid degeneration and to address the clinical significance of these entities.

MATERIALS AND METHODS: A database search of 4221 knee MRI examinations over 2 years revealed 90 examinations with reported anterior cruciate ligament ganglion or mucoid degeneration. Imaging criteria for ligament ganglion included fluid signal in the ligament disproportionate to joint fluid showing mass effect on intact ligament bundles. The size, location, complexity, and degree of lobulation of ganglia were recorded. Criteria for mucoid degeneration included ligament bundles poorly seen on T1-weighted and proton density-weighted images but with both bundles seen as intact on T2-weighted images. Intraosseous cysts at the ligament attachments and presence of joint effusion were noted. Clinical assessment of ligament instability was recorded when available.

RESULTS: Of 74 examinations that met imaging criteria, 56 (76%) had discrete intraligamentous ganglia, 18 (24%) had mucoid degeneration, and 26 (35%) had features of both. Ganglia were located in the proximal ligament in 16 examinations (22%) and the distal ligament in 10 (14%) and involved the entire ligament in 30 (40%). Ganglia ranged in maximum diameter from 20 to 73 mm (mean, 31 mm). Complexity of ganglia was mild (41%), moderate (39.2%), or marked (19.8%). Intraosseous cysts were noted proximally in 48 examinations (65%) and distally in 20 (27%). Of 52 patients with accessible records, 48 had no clinical evidence of instability. Twelve patients who underwent arthroscopy had an intact anterior cruciate ligament at that time.

CONCLUSION: Anterior cruciate ligament ganglia and mucoid degeneration commonly coexist on MRI and are typically not associated with ligament instability.