Fig. 2

Regional subdivision of the articular surfaces. In the axial plane, the patella (left image) is divided into medial (M) and lateral (L) regions, with the ridge considered part of the M region. In the coronal plane, the femur and tibia are also divided into M and L regions, with the trochlear groove of the femur considered part of the M region. The spines (S) region represents the portion of the tibia beneath the tibial spines. In the sagittal plane, the femoral and tibial surfaces are further subdivided into anterior (A), central (C), and posterior (P) regions (middle image). Region A of the femur corresponding to the patellofemoral articulation; region C to the weight-bearing surface, and region P to the posterior convexity that articulates only in extreme flexion. Region C of the tibial surface corresponds to the uncovered portion between the anterior and posterior horns of the meniscus centrally and the portion covered by the body of the meniscus peripherally