MRI-based kinematics of the menisci through full knee range of motion

The meniscal kinematics in the full knee range of motion (ROM) have not been demonstrated by MRI, because the narrow bore of the superconducting magnet prevents full knee motion. The purpose of this study was to the investigate meniscal kinematics associated with femorotibial kinematics using an open-structure MRI unit that allows kinematic analysis of the menisci in full knee ROM.

Non-weight-bearing MR images of the right knee of 10 subjects were acquired at six angles of knee flexion (0°, 30°, 60°, 90°, 120°, and full flexion) using a compact 0.2-T MRI system. The positions of the anterior and posterior horns of the medial and lateral menisci (MM/LM) and the medial and lateral femoral condyles (MFC/LFC) were measured at each angle of flexion.

Significant posterior LFC movement was observed in all sets of adjacent flexion angles of 60°-90° or more, indicating medial pivot motion of the femur. Significant differences in LM position were observed between adjacent flexion angles of 60°-90° or more. The positional relationship between the posterior horn of MM and the MFC was statistically significant in all but 60° flexion. The positional relationship between LM and LFC was significant at flexion angles of ≤90° in the anterior horn and at 60°, 90°, and full flexion in the posterior horn.

Motion patterns of the menisci were analogous to those of the femoral condyle. Medial pivot motion of the femur caused the greatest posterior movement of the LM. Meniscal kinematics followed the femorotibial kinematics. Comprehension of meniscal kinematics in full knee ROM is important for understanding of injury mechanisms, planning meniscus transplant, and making postoperative care program for meniscus surgery.