Posterior cruciate ligament recess and normal posterior capsular insertional anatomy: MR imaging of cadaveric knees.

Abstract

PURPOSE: To analyze the normal pattern of fluid accumulation adjacent to the posterior cruciate ligament and anatomic variations of joint capsule insertion sites in the posterosuperior corner of the human knee by using magnetic resonance (MR) imaging in cadaveric specimens.

MATERIALS AND METHODS: Fourteen fresh cadaveric knees (obtained and used according to institutional guidelines, with informed consent from relatives of the deceased) from 11 men and three women (six left knees, eight right knees; age range, 70-82 years at time of death; mean age, 76 years +/- 4.4 [standard deviation]) were studied with high-spatial-resolution MR imaging performed before and after intraarticular injection of 35-45 mL gadopentetate dimeglumine. MR images were evaluated by two readers in consensus, with emphasis on location of fluid posterior to the posterior cruciate ligament, communication of that fluid with the medial or lateral compartment of the knee, and the relation of fluid to surrounding structures. Readers also were asked to measure, in the sagittal plane, the distance between the posterior capsular insertion sites and the femoral physeal scar. For anatomic analysis, cadaveric specimens were sectioned in 3-mm-thick slices in the sagittal plane that approximated the sections acquired at MR imaging.

RESULTS: In all 14 cadaveric specimens, MR arthrographic images showed a fluid collection behind the posterior cruciate ligament (in the posterior cruciate ligament recess), a finding not evident on images obtained prior to contrast material injection. The recess was distended during flexion, and it communicated only with the medial femorotibial compartment in all cases. Posterior to the posterior cruciate ligament recess, a fat pad was observed in all specimens. Incomplete joint capsule was seen behind the fat pad in seven specimens. Joint capsule insertion was at the level of the femoral physeal scar or between it and a point 15 mm above it.

CONCLUSION: The posterior cruciate ligament recess has specific characteristics that allow its identification: communication with the medial compartment of the knee and absence of the adjacent joint capsule.