The purpose of this prospective study was to develop and evaluate a method for measuring the femorotibial joint space and to assess the effect of meniscectomy.

This study was conducted in a consecutive series of 36 patients undergoing arthroscopic meniscectomy for lesions of the medial meniscus on a stable knee. The height of the joint space was measured on x-rays taken in the morning before the operation then ten days later. X-rays were obtained for both knees in complete extension and in the 30° flexion position. The height of the joint space was measured on the digital version of the x-rays midway between the vertical tangents of the posterior limits of the medial condyle.

Readings were not reader dependent and demonstrated no significant difference between the pre and postmeniscectomy height of the medial femorotibial space (30° flexion view, 5.2 ± 1 and 5.2 ± 1 before meniscectomy for reader 1 and 5.2 ± 1 and 5.2 ± 1 for reader 2 (p = 0.05 for Student-Fisher test for paired values). The heights measured by the two readers were correlated (correlation coefficient test).

The height of the medial femorotibial joint space can be measured reproducibly on plain x-rays of the knee in the standard flexion position. We were unable to demonstrate any significant difference in joint space between measures taken before and after meniscectomy.