Medial meniscal cyst of the knee simulating a solitary bone lesion. A case report and review of the literature.

Meniscal cysts are common lesions, but extensive bony changes arising from these cysts are exceedingly rare. These changes are usually erosive defects about the tibia. Dull pain with an associated mass are classic findings. Magnetic resonance imaging is useful in making the diagnosis and arthroscopic management yields excellent results. A 47-year-old man developed a symptomatic medial meniscal cyst that invaded the medial femoral condyle simulating a solitary bone lesion. Magnetic resonance imaging revealed the contiguous nature of the cyst with the meniscus. Arthrotomy with cyst excision was required in this case and led to the amelioration of symptoms.