[Ultrasonography in the study of lesions of the menisci and the collateral ligaments of the knee. Findings in 48 surgically treated patients].
The authors report the results of the study of 48/112 patients who underwent US examination of the knee for gonalgia. Meniscopathy or capsular-ligamentous lesions were clinically suspected. US results were compared with arthroscopic or athrotomic findings; the latter two methods were considered as the reference gold standard. US exhibited 81.2% overall diagnostic accuracy, thus confirming its limitations, more evident than those of arthroscopy and arthrography, CT and MR imaging. Major limitations of US were its failed recognition of meniscal tears smaller than 5-6 mm, and its failed distinction of degenerative meniscopathies from common meniscal fractures (with the exception of 2 cases). Moreover, US did not allow cruciate ligament lesions to be demonstrated; however, in all these cases, US did demonstrate increased capsular thickness (greater than 3 mm at the lower margin of femoral condyle). This indirect sign, together with roudness of parameniscus and capsular-ligamentous limitans (at the hemirhyme), and the direct sign of inhomogeneous hyperechogenicity of the meniscal triangle (normally hypoechoic) contributed to raising overall diagnostic accuracy of US to 89.9%. In the 5 patients with a suspected lesion of the medial collateral ligament examined within 48 hours from trauma, US gave 2 false-positive results in 2 cases where forced abduction test was also positive. Massive edema and swelling of adjacent structures prevented the correct evaluation of ligament limitans. In these 2 cases, a lesion in the anterior cruciate ligament was found at surgery; one of them was associated with a meniscal lesion already diagnosed at US. Both parameniscal and popliteal cysts were correctly diagnosed with US. Due to the well-known limitations of clinics in the diagnosis of knee pain, US could be suggested as the examination of choice to evaluate suspected meniscopathy or ligamentous lesions, thanks to its low cost and short execution time. The use of US could also spare the patients more invasive examinations--e.g., arthroscopy and arthrography--and more expensive ones--e.g., CT and MR imaging.