Lateral radiograph illustrating articulation of the knee joint
The human knee is a massively complicated system of muscles, bone articulations, tendons, ligaments, and bursae. Given that over 300% of the body weight is exerted upon the knee when you're doing nothing more than walking (and nearly 600% while running), is it any surprise that it's the most common joint needing operation? Atlas for Electro-diagnosis and Therapeutics. F. Miramond de LaRoquette, translated from German by Mary Gregson Cheetham, 1920.