Synovial Disorders and Cystic Lesions of the Knee

The synovium is a specialized vascular tissue that plays an important role in the lubrication and nourishment of articular structures, as well as serving as a shock absorber within the knee. Synovium also lines tendons sheaths and bursal spaces around the knee. Synovial disorders of the knee are common and can result in significant morbidity. The synovium can be affected by a variety of processes including trauma, osteoarthritis and inflammatory arthropathies, infection, and neoplastic disorders. Some synovial-based pathologies can be detected on radiographs, ultrasound, and CT, including joint effusions, synovial-based soft tissue masses, and secondary osseous changes. However, MRI with its superior soft tissue contrast and multiplanar imaging capabilities allows a more comprehensive evaluation of synovial-based processes and secondary bony changes, providing the orthopedic surgeon with valuable diagnostic information that may facilitate surgical or therapeutic intervention prior to irreversible joint damage. This chapter will review the clinical examination of patients with synovial-based pathology, discuss clinical indications for imaging, and review the different synovial processes that can affect the knee joint, as well as synovial-lined structures around the knee.