Sunday, July 04, 2010
The knees are a marvel of engineering. They are the largest and most complex joints in the human body.
We usually take the knee joints for granted, however without them our legs would be almost useless logs. Walking, running, sitting down and so on would be impossible without the knees.
The knee is essentially made up of four bones. The femur, which is the large bone in your thigh, attaches by ligaments and a capsule to your tibia. Just below and next to the tibia is the fibula, which runs parallel to the tibia. The patella, or what we call the knee cap, rides on the knee joint as the knee bends.
When the knee moves, it does not just bend and straighten, or, as it is medically termed, flex and extend. There is also a slight rotational component in this motion. This component was recognized only within the last 50 years. The knee muscles which go across the knee joint are the quadriceps and the hamstrings. The quadriceps muscles are on the front of the knee, and the hamstrings are on the back of the knee. The ligaments are equally important in the knee joint because they hold the joint together. In review, the bones support the knee and provide the rigid structure of the joint, the muscles move the joint, and the ligaments stabilize the joint.
The knee joint also has a structure made of cartilage, which is called the meniscus or meniscal cartilage. The meniscus is a C-shaped piece of tissue which fits into the joint between the tibia and the femur. It helps to protect the joint and allows the bones to slide freely on each other. There are also bursae around the knee joint. A bursa is a little fluid sac that helps the muscles and tendons slide freely as the knee moves.
As an avid runner (about 20 miles per week), I'm very conscious of the need to care for the knees and not to over strain them. With sensible and proper care, the knee joints should give a lifetime of faithful service.
Unfortunately, in some cases the knees become badly damaged, usually by some form of arthritis. Obesity is an important risk factor. Starting about 40 years ago, doctors began having some success replacing the knee with an artificial joint made of plastic, ceramic and metal. A knee replacement costs about $35,000. The artificial knee may last up to 20 years. However it has limitations; running for example is not recommended. The less the artificial joint is used, the longer it will last. No matter how great modern technology is, it cannot replace the complexity of the natural knee joint. The replacement is not a normal knee.
Those of us who still have healthy, functioning knees should be filled with gratitude and love for our Creator and each morning fervently recite the prayer "Blessed is He who makes firm the steps of man" (Talmud Tractate Berakoth 60b)
Posted by jewish philosopher at 4:52 PM