Distribution of joint effusion in patients with traumatic knee joint disorders: MRI assessment.

One hundred forty-five knee magnetic resonance imaging examinations with joint effusions were reviewed to clarify the usual distribution of joint fluids in patients with traumatic knee joint disorders. Almost all knees (99%) had effusions in the central portion, and most knees (76%) had effusions in the suprapatellar pouch. Effusions were rarely found in the posterior femoral recess (9%) or subpopliteal recess (2%). However, this difference was considered to be only a reflection of anatomic communications. Effusions were occasionally found around posterior cruciate ligaments (36%), but were less frequently seen around anterior cruciate ligaments (18%).