MRI characteristics of cysts and “cyst-like” lesions in and around the knee: what the radiologist needs to know

Abstract

Objectives and MethodsA variety of benign cystic or “cyst-like” lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee. These lesions comprise a diverse group of entities from benign cysts to complications of underlying diseases. In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended. However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.ResultsThis article includes a comprehensive pictorial essay of the characteristic MRI features of common and uncommon benign cysts and “cyst-like” lesions in and around the knee joint.DiscussionFor accurate assessment of the “cystic structure”, a radiologist should be able to identify typical MRI patterns that contribute in establishing the correct diagnosis and thus guiding specific therapy and avoiding unwarranted interventional procedures such as biopsy or arthroscopy.Teaching points• Cystic lesions are common in knee MRI and the commonest, the Baker’s cyst, has an incidence of 38 %.• Synovial cysts, meniscal cysts, normal knee bursae and recesses have characteristic MR appearances.• Miscellaneous “cyst-like” lesions may require a more dedicated MR protocol for a correct diagnosis.

Soft tissue pseudotumours: a pictorial review with emphasis on MRI

“…Tendon ganglion cysts are defined as benign cystic lesions that usually arise from the tendon sheath, are surrounded by dense connective tissue, and are filled with a gelatinous fluid rich in hyaluronic acid and other mucopolysaccharides 22,23 . At MRI, the lesion may be rarely interspersed within the tendon fibers, but usually occurs along the tendon sheath (tendon sheath ganglion cysts), and thus the MR imaging appearance is fairly typical 22,23 .…”

“…At MRI, the lesion may be rarely interspersed within the tendon fibers, but usually occurs along the tendon sheath (tendon sheath ganglion cysts), and thus the MR imaging appearance is fairly typical 22,23 . On T2-weighted MR images, ganglia appear with high signal intensity, whereas, on T1-weighted MR images, the signal intensity of ganglia depends on their protein content.…”

“…Associated bony erosion and pericystic oedema have been reported. In such instances, differentiation from more aggressive soft tissue 'masses" may be required 22,23 (Fig. 11).…”

“…As with tendon ganglion cysts, they are cystic lesions, and typically arise from chronic traumatic injury of the ligament [22][23][24][25] . Part of the lesion may be interspersed within the ligament fibers, or lying entirely adjacent to the ligament, or it may extend occasionally in the surrounding soft tissues.…”

“…Part of the lesion may be interspersed within the ligament fibers, or lying entirely adjacent to the ligament, or it may extend occasionally in the surrounding soft tissues. An unilocular or multilocular appearance has been described, and MRI is the modality of choice for correct identification, especially in lesions located in the deep soft tissues [22][23][24][25] (Fig. 13).…”