Le profil du genou. Anatomie radiologique différentielle des surfaces articulaires.

On lateral roentgenograms, the articular surfaces of the knee are characterized by specific landmarks that enable to differentiate them. We looked for the incidence of these characteristics on lateral views of the knees in 40 unselected patients. In our observations, several signs are virtually constant: the visualisation of the external portion of the lateral patellar facet (100%), the concave configuration of the medial tibial condyle (100%), the groove of the middle third of the lateral femoral condyle (90%), and--as a new sign--the sharper aspect of the lateral border of the patellar surface of the femur in comparison with the medial border (87.5%). Other characteristics, less constant but also useful, are the convex configuration of the lateral tibial condyle (62.5%), the more cranial extension of the lateral border of the patellar surface of the femur in comparison with the medial (57.5%), and the groove in the anterior part of the medial femoral condyle (47.5%). These anatomic characteristics are linked with the specific functional characteristics of each compartment. For instance, the lateral preponderance of patello-femoral stresses accounts for the better visualization of both the lateral patellar facet and the lateral border of the patellar surface of the femur; the great anteroposterior mobility of the lateral femoral condyle on the corresponding tibial condyle during the rotatory motion of the knee is facilitated by the convex configuration of both; finally, the femoral condylar grooves are the mirrors of the anterior part of the tibial condyles with which they make contact when the knee is full extended (with meniscal interposition in the lateral but not in the medial compartment, as it was proved by 20 full extended arthrographic views). Besides, it seems that the development of some inconstant anatomic details is probably correlated with knee laxity.