A new in vivo technique for the three-dimensional analysis of femoral and meniscal translation under the influence of antagonistic muscle forces

The aim of our study was to develop a 3-D MR-based technique for the analys is of meniscal and femoral translations during flexion of the knee, and und er the influence of antagonistic muscle forces in healthy subjects. In an open MR system, 5 knees were examined at 30 degrees and 90 degrees fl exion using a T1-weighted 3-D gradient echo sequence. A force of 30 Newtons , first in the extending and then in the flexing direction, was applied to the distal lower leg. After three-dimensional reconstruction, the minimal d istances between the centre of the tibial plateau and the posterior edge of the menisci and femoral condyles were determined. At 30 degrees flexion, the minimum distance for the meniscus was larger med ially than laterally (23.2 +/- 1.8 mm vs. 16.2 +/- 3.3 mm), and this also a pplied to the condyles (25.1 +/- 1.5 vs. 19.0 +/- 3.0 mm). During flexion t o 90 degrees, a posterior translation of 0.5 +/- 0.2 mm was observed for th e lateral, and of 3.4 +/- 1.2 mm for the medial, meniscus. The condyles dem onstrated a different posterior translation (lateral 2.2 +/- 0.56 mm; media l 1.8 +/- 1.9 mm). No obvious differences were found between extension and flexion muscle activity for the different positions of the knee. In the present study, a new 3-D technique is presented for the analysis of the femoral and meniscal translation at various positions of the knee, and under muscle activity. The results suggest different translation for the me nisci and condyles.