Sonography of the knee: intra-articular pathology.

MRI is the gold-standard imaging technique for evaluation of the intra-articular structures of the knee, and the use of sonography remains controversial. Sonography nevertheless is a useful alternative in several conditions: Inflammatory joint diseases, where it is appropriate for early diagnosis and follow-up of joint effusion and synovitis; peri-articular masses, where it is the best modality for guidance of needle puncture or biopsy; suspected meniscus or ligament lesion, where it may provide a positive diagnosis but is not sufficient to exclude intra-articular lesions; and loose bodies, where it is an outstanding modality for diagnosing lesions not evident on radiographs.