Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation.

OBJECTIVE: The purpose of our study was to define retinacular anatomy with MR imaging and sonography.
MATERIALS AND METHODS: Five cadaveric knee specimens underwent sonography and MR imaging using the following sequences: T1-weighted axial, sagittal, coronal, and five oblique planes and axial three-dimensional gradient-echo imaging. Three knees were injected with gelatin gadolinium solution before imaging. All five specimens were sectioned. Correlation was made between findings derived from MR imaging, sonography, and cadaveric sections.
RESULTS: T1-weighted axial images without intraarticular gadolinium were most useful for revealing the superficial layer and deep ligaments of the retinacula; however, the oblique sagittal and oblique coronal planes showed the deep ligaments more clearly in their craniocaudal dimensions. Sonography revealed the retinacula as bilaminar structures with discrete superficial and deep layers but failed to distinguish the deep ligaments from one another.
CONCLUSION: Conventional T1-weighted axial MR images showed the various components of the retinacula including the medial patellofemoral ligament, which is an important stabilizing structure. Oblique imaging planes may be a helpful adjunct to axial imaging planes. Sonography can consistently identify the retinacula and may be useful in their assessment.