Cystic Lesions about the Knee eMedicine Orthopedics

Description: Cysts can occur in many shapes and forms around the knee. A cyst is defined as a closed cavity, or sac, that is lined with epithelium. It can contain liquid or semisolid material, can be normal or abnormal, and can occur in soft tissue or in bone. Benign or malignant masses must be distinguished from cystic lesions. This article discusses benign cysts that occur in the soft tissue around the knee or outside bone and that are filled with fluid or semisolid material. The understanding of various knee cysts is highly dependent on a thorough knowledge of the anatomy of the knee, which is a highly mobile structure. Bursae, sacs or saclike structures that are located at places where friction develops between the soft tissues and around the bony prominences, line many of the ligaments, tendons, and bony prominences around the knee. They can be lined with synovium and respond much the way synovium does to insults and pathologic conditions. Bursae can fill with fluid, and this accounts for the large majority of cysts seen around the knee.
Synonyms and related keywords: benign soft tissue cysts about the knee, knee cysts, meniscal cysts, popliteal cysts, bursae, bursitis, housemaid's knee, carpet layer's knee, fluid cyst, semisolid cyst, ganglion cysts, intraneural cysts, popliteal artery cysts, rheumatoid arthritis, osteoarthritis, blood-filled bursae, pus-filled bursae, myxoid intraneural cysts
Author: David M Gonzalez, MD 2007