Another musculoskeletal injuries associated with patient related care is injury to the lower extremities. Particularly the knee. Knee joints are somewhat unstable structures. Subject to articular cartilage deterioration and ligament injury. Articular cartilage covers the ends of the leg bones making the ends slick enabled to easily slide over one and other. It absorbs shock and provides a smooth surface to facilitate motion. The mechanism of injury to the knee is through slips, trips, falls, sustained awkward positions and unexpected forces. There are four essential ligaments that provide support for the knee; the medial collateral ligament (MCL), the lateral collateral ligament (LCL), the anterior cruciate ligament (ACL) in front and the posterior cruciate ligament or PCL in the back of the knee. The MCL and LCL prevent the knee from moving too far in the side to side direction. The ACL and PCL control the front to back motion of the knee joint. The ligaments all taken together are the most important structures controlling the stability of the knee. Menisci, are special types of ligaments located between the femur and the tibia but help stabilize the component of the knee and distribute the force generated from the weight of the body. The menisci are thicker around the outside and this thickness keeps the round femur from rolling on the flat tibia. Without the menisci, the concentration of force into a small area on the articular cartilage can damage the surface and over time lead to degeneration. The mechanism of injury from many ACL ruptures is a sudden deceleration, hyperextension or pivoting motion. Recent research indicates that due to basic anatomical differences, women run a greater risk of suffering an injury to their anterior cruciate ligament than men. And some studies suggests that women's ACLs may be weakened by the effects of the female hormone; estrogen. As we have noted, there are numerous muscles, tendons and ligaments that can be affected during the course of performing a job. While it is not possible to anticipate every potential source of injury being aware of the most common injury sites and the tasks that may lead to injuries and the nature of the injury itself is the first step to creating a safe working environment.