Ultrasonography of the Knee.

Musculoskeletal ultrasonography (MSUS) is a radiologic modality that can help in the evaluation of the knee and its lesions. Both soft tissue and surface bony structures can be sonographically visualized. The extra-articular structures of the knee can be evaluated, specifically the ligaments, bursae, and tendons. Collateral ligaments and the extensor mechanism, especially quadriceps and patellar tendons, are readily visualized. The diagnosis of a Baker's cyst and its complications is a common indication. The intra-articular structures of the knee, with proper maneuvers and transducers, can also be evaluated. The femoral condylar and patella cartilage can be examined for traumatic or degenerative lesions. The anterior and posterior cruciate ligaments can be partially visualized directly, or evaluated indirectly. Loose bodies are readily detectable whether intra-articular or extraneous in a Baker's cyst. Synovial disease can be characterized without the use of radiographic contrast. MSUS can be used as a screening, diagnostic or follow-up radiologic tool in the diseases of the knee.