To describe and illustrate the imaging features of mucoid degeneration of the anterior cruciate ligament (ACL) Demonstrate how to distinguish mucoid degeneration of the ACL vs partial tears

Mucoid degeneration of the anterior cruciate ligament (ACL) is an uncommon cause of a painful knee of which the exact pathogenesis is unclear. Some advocate it is simply a consequence of senescent degeneration whilst others suggest it is related to acquired or congenital synovial tissue herniation1 or is a consequence of mild non-specific trauma2-4. There is no fixed presentation and it often mimics other internal pathologies of the knee with progressive knee pain, restricted range of movement but without knee instability4,5. It is predominantly a...

Characteristic MRI appearances of mucoid degeneration MRI is the gold standard modality for diagnosis of mucoid degeneration. It is visualised as a bulky ligament with increased signal on all pulse sequences, with ligament bundles and fibres readily distinguished on T2-weighted images (T2WI) and fluid sensitive sequences such as fat saturated proton density images (PDFS) but not well seen on T1-weighted images (T1WI)9 (Figure 1). The characteristic feature of mucoid degeneration is a diffusely thickened ACL with intact ligamentous fibres spread apart by high signal intensity...

Conclusions Careful interrogation of the ACL in axial, coronal and sagittal planes allows the radiologist to accurately differentiate between mucoid degeneration of the ACL versus partial tears. Lack of ancillary MRI findings associated with ACL injury, in addition to an absence of clinical features to suggest ACL injury, are useful additional discriminators. Intra-ligamentous ganglion cysts are another imaging differential of mucoid degeneration and may be part of the same process as the two are often seen in association. Table 3 highlights the main clinical and...

MelloniP, Valls R, Yuguero M, Saez A. Mucoid degeneration of the anterior cruciate ligament with erosion of the lateral femoral condyle.Skeletal Radiol2004;33:359–362. KumarA, Bickerstaff DR, Grimwood JS, Suvarna SK. Mucoid cystic degeneration of the cruciate ligament.J Bone Joint Surg Br1999;81:304–305. McIntyre J, Moelleken S, Tirman P: Mucoid degeneration of the anterior cruciate ligament mistaken for ligamentous tears. Skeletal Radiol 2001 Jun; 30(6): 312-5) Fealy S, Kenter K, Dines JS, et al. Mucoid degeneration of the anterior cruciate ligament.Arthroscopy.2001;17:1–4. Maikano A, Pascual-Garrido C, Rolon A, et...