What type of cyst is typically calcified, particularly around the knee in adults with a history of joint issues or trauma?

Meniscal Cyst

The cyst most characteristically associated with calcification in the knee region is a meniscal cyst, though calcification is uncommon; ganglion cysts can also rarely calcify.

Primary Calcifying Cyst Types

Meniscal Cysts

• Meniscal cysts arise from degenerative tears in the meniscus and can occasionally demonstrate calcification on imaging 1
• These cysts typically present in adults with a history of joint trauma or degenerative changes 1
• The knee is the most common location for lower extremity ganglion-type cysts, accounting for 33% of cases in surgical series 1

Ganglion Cysts

• Ganglion cysts are fibrous-walled cystic lesions containing gelatinous mucinous fluid that arise close to joints or tendons 2, 3
• Calcification or ossification in ganglion cysts is extremely unusual but has been documented 4
• In the knee, ganglion cysts commonly arise from the anterior cruciate ligament but can also originate from the posterior cruciate ligament or meniscus 2
• Lower extremity ganglia occur most commonly in the fifth and sixth decades of life, with a female predominance 1

Imaging Characteristics

Radiographic Findings

• The radiographic appearance of ganglion cysts is usually normal, as they are soft tissue lesions 4
• When calcification does occur, it can resemble myositis ossificans on plain films 4
• Ultrasound can detect ganglion cysts and confirm fluid content in the appropriate clinical setting 5

Advanced Imaging

• MRI is the investigation of choice for diagnosis of intra-articular ganglion cysts 2
• Ultrasound guidelines specifically list "calcifications" as detectable pathology around the hip and knee joints 5

Clinical Context

Presentation

• Patients may present with pain, radiculopathy, or be completely asymptomatic 2, 6
• Some patients report a history of trauma 2
• Ganglia may mimic other intra-articular lesions like meniscal tears or ACL tears 2

Important Caveat

While the question asks about calcified cysts, it's critical to recognize that calcification in ganglion or meniscal cysts is the exception rather than the rule 4. Most cystic lesions around the knee remain non-calcified throughout their natural history 3, 4.