The knee is a complex joint. It contains the distal end of the femur (the femoral condyles) and the proximal end of the tibia (the tibial plateau). The femoral condyles usually glide smoothly on the tibial plateau. This allows the lower leg to move smoothly and painlessly.
Update Date 1/22/2014
Updated by: Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.