A Divine but Natural Phenomenon
Crisscrossing ligaments, articulating bones and cartilage, synovial membranes secreting lubricating fluid, tendons of muscles, and friction-erasing bursa all converge at this minimalized ball-and-socket joint–to do what? To create the miracle of movement–to make fluid human locomotion, whether fast or slow, possible. Moving the yearold child from the floor to its mother, sending the shopper through the store stalls, launching the penitent to seek forgiveness, propelling the runner around the Olympic track. Bearing the weight of its owner′s body multiplied by the force of that body in movement, the knee is a divine but natural phenomenon that when working well is taken for granted. But when the knee is injured or malfunctioning, its loss can escalate annoyance to grief and evoke a pain and discomfort beyond that attributable solely to the injury.
The knee is second only to the ankle in vulnerability to bone or ligament injuries, and knee injuries cause much greater impairment. More than half of the American population participates in sports activities every year, and of these participants millions will experience a knee injury. In fact, 19.4 million visits to physician offices in 2003 were because of knee problems. Even among those who are not participants in sports, conversations about aches and pains often center around knee injuries of their own, their peers, or their athletic heroes.
The knee is the fulcrum on which is determined superiority or inferiority, resistance or submission, strength or weakness. Because walking upright sets humans apart from their nearest living relatives, the knee′s characteristics have been crucial in anthropological studies to identifying which family–human or ape–newly discovered fossils belonged. To be "upright" is to be superior, literally and figuratively.
Conversely, for thousands of years, the bent knee has indicated submission. As a gesture of respect, some children are taught to curtsy, bending their knees and sometimes lowering their heads. People of all ages around the world kneel to demonstrate submission to their god, and many kneel to indicate reverence for religious or political leaders or religious icons. Language symbolically reflects this thinking. Problems of all sorts–emotional, financial, and political "injuries"–"bring us to our knees."
This well-worn and symbolically charged joint, whose surface is familiar geography to every schoolchild, quickly develops in the womb despite its complexity. The eight-week embryonic development of the human proceeds from head to toe, so to speak, meaning that the arms develop before the legs. When the embryo is less than one-fourth inch and only about twenty-four days old, an arm "bud" develops, followed within two days or less by the leg "bud." When the embryo is not yet three-quarters of an inch, the femur, tibia, and fibula appear and the kneecap is evident. When the embryo is about forty-one days old, but still less than an inch long, the knee zone is formed. Within four more days, the knee ligaments appear, and within two more–with the embryo at the ripe old age of forty-seven days–the knee clearly resembles that of an adult.
Though this embryonic development is unbelievably rapid, the knee′s history stretches back about 320 million years.
This is a section from Dr. Jack E, Jensen’s book The One Stop Knee Shop. Read the next section Evolution of the Knee.