Mucoid degeneration of the anterior cruciate ligament: magnetic resonance imaging findings of an underdiagnosed entity

Abstract

Although imaging and clinical criteria are already established for the diagnosis of mucoid degeneration of the anterior cruciate ligament (ACL), many radiologists remain unaware of their existence. Once regarded as a rare occurrence, it has been recently suggested that its incidence is in fact very much higher than previously thought, and that it is probably underdiagnosed or misdiagnosed as partial ruptures of the ACL or as cystic ganglia. In this review, the authors revisit the literature concerning this subject and present their personal experience with it, stressing the paramount importance of magnetic resonance imaging and correlation with clinical data for a correct diagnosis.

Mucoid degeneration of the anterior cruciate ligament: Management and outcome

“…With joint and tissue motion, the mucin substance dissects the ligament fibers and gets interspersed within the fibers of the ligament, causing its fusiform dilatation 17. Other theories include “Degenerative” theory which states that MD could occur due to ageing 11118. “Ectopic” theory is an interesting hypothesis wherein ectopic synovial tissue could exist inside ACL substance giving rise to microcyst formation 314.…”

“…review of 4221 knee magnetic resonance imaging (MRI) revealed that 1.8% ( N = 74) of knees can be affected with MD ( N = 17) and mucoid cyst ( N = 57) 8. Regarded as a rare occurrence in the past, of late many reports of MD have highlighted the fact that it is not a rare entity and possibly was under diagnosed or misdiagnosed and reported as partial or complete tear of ACL 23579101112. The Purpose of this prospective study is to discuss the clinical, radiological, arthroscopic features, treatment and outcome in eleven such patients.…”

Cysts and cystic-appearing lesions of the knee: A pictorial essay

“…Anterior cruciate ligament (ACL) ganglia are more common than posterior cruciate ligament (PCL) ganglia and can have a “drumstick” appearance with enlargement and increased T2 signal in the proximal ACL fibers[12] [Figure 12]. This increased T2 signal can be seen as a discrete focus of fluid or a more diffuse abnormality of “mucoid degeneration.” It is important to distinguish ACL ganglia from a ligament tear because patients with ACL ganglia do not have instability and are usually asymptomatic.…”

“…[13] Although lateral cysts are more common in the arthroscopic literature, medial parameniscal cysts are 2 times more common than lateral cysts in the radiologic literature. [12] Medial meniscal cysts are typically associated with posterior horn tears, whereas lateral meniscal cysts arise from anterior horn and body tears. [313] Lateral cysts are more symptomatic, with patients presenting with a painful palpable lump, which may account for its higher prevalence in the arthroscopic literature.…”

Metastatic adenocarcinoma of the lung mimicking mucoid degeneration of the anterior cruciate ligament

“…Mucoid degeneration of the ACL has also been reported to cause erosion of the adjacent femoral cortex [7] which mimics tumour behaviour. This case highlights the difficulties in interpreting the non-specific appearance of the ACL and adjacent femoral cortex in suspected mucoid degeneration as the differential diagnosis of these MRI findings also includes ganglion cysts and partial ligamentous tears [1,8] as well as intraarticular metastasis.…”