ABOUT THE KNEE: The knee is made up of three bones designed to produce smooth, stable motion: the shinbone (tibia), the thighbone (femur) and the kneecap (patella). The bones are enclosed in the joint capsule, which is lined with a tissue that produces a thick liquid to keep the joint lubricated and nourished. The knee is kept in alignment by ligaments and tendons. The anterior cruciate ligament (ACL) is one of two major stabilizing ligaments of the knee joint. The other one starts at the back of the knee -- the posterior cruciate ligament. These two ligaments cross each other at the center of the knee. There is another set of stabilizing ligaments on either side of the knee as well, which stabilize the joint when the knee moves from side to side.
ABOUT FRACTURES: A fractured bone is the same thing as a broken bone. They occur because a bone area is unable to support the energy placed on it. That energy can be acute, as from a car crash or a two-story fall, or chronic due to low-energy repetitive activity. The latter is responsible for stress fractures, an overuse injury commonly seen in athletes. The increased demand places on the bone causes it to remodel and become stronger in areas of higher stress, but if the repetitive demands become too great, a stress fracture can result.The Biophysical Society contributed to the information contained in the TV portion of this report.