The knee was a compound joint linking the thigh and the leg, specifically the femur and tibia and the femur and patella. Going to one's knee or bending one's knee was in many cultures considered an act of submission or respect. (TOS: "Who Mourns for Adonais?" , "Return to Tomorrow" ) The symptoms of kaylo poisoning included a sharp pain in the knees working its way up the body. (VOY: "State of Flux") While exploring a comet in 2151, Travis Mayweather injured his knee. (ENT: "Breaking the Ice") Ekoria planned to kiss the knee of her unborn son when he scraped it in a fall. (DS9: "The Quickening")