**7. Joint line position**

Since restoration of joint line can be difficult in severe osteoarthritic knee with coronal and sagittal plane deformities, many surgeons prefer the use of a PS TKR, which is less sensitive to changes in joint line position: in fact, the level of the reconstructed joint line is one of the main factors that affects the tension of the retained PCL [21]. As reported by Emodi et al. in a cadaveric study "As the joint line was elevated, PCL strain increased at all measured flexion angles above 30°…" and "…the centre of tibio-femoral contact did not change at the flexion angles of 15 and 30°…" but "…at 60, 90 and 105° the tibio-femoral contact centre moved posteriorly with each successive elevation of the joint line." This author also confirmed what already reported in literature that "…Significant decreases in flexion were observed with as little as 2 mm of elevation. Flexion was limited further as the joint line was elevated 4 and 6 mm, and was partially restored following cruciate excision…" and "… The effect of joint line elevation on normalized quadriceps load and patella-femoral contact pressures was observed only at higher flexion angles…" [22].
