Fig. 1
From: Factors that impact the patellofemoral contact stress in the TKA: a review
Diagram of the arm and moment of a patellofemoral joint under weight-bearing conditions. A FHA = finite helical axis, CG = the body’s center of gravity; F1 = body gravity, L1 = moment arm of F1; F2 = the resultant of the quadriceps and patellar tendon forces (i.e., the patellofemoral reaction force), L2 = moment arm of F2. B When balanced, the moment of F1 is equal to that of F2 (F1 × L1 = F2 × L2), simplified as the mode of the lever