Primary osteoarthritis is the result of long-term activity of the knee joint in the elderly, like a grinding wheel that often rotates and wears each other out, causing degenerative changes in the bone and cartilage as they age, gradually forming bone spur-like growths. Secondary osteoarthritis is the result of trauma, fractures, dislocations and other diseases in the knee joint, resulting in osteophytes in the bone and cartilage, and changes in the physiological function of the knee joint. Overweight, improper walking and working posture are often the causes of this disease. Primary osteoarthrosis is mainly due to the degenerative aging of the articular cartilage that increases with age. The causes of degenerative aging of articular cartilage are related to the “wear and tear” of the area in question, the progression of the disease, and high levels of fatigue and overload. How to reduce bone and joint injuries in daily work? We may want to learn some knowledge of human body mechanics. The correct use of the principles and laws of human body mechanics can reduce the occurrence of orthopedic diseases, guide the treatment of trauma, promote functional rehabilitation and prevent complications. Human body mechanics knowledge drops The human body moves in various forms, but most of them are the application of the principle of leverage. A lever is a rod that can rotate around a fulcrum. There are three basic forms of levers: balance levers, where the fulcrum is located between the point of resistance and the point of force; labor-saving levers, where the point of resistance is located between the fulcrum and the point of force; and speed levers, where the point of force is located between the point of resistance and the fulcrum. The human body uses the principle of speed leverage the most, but there are also balance levers and force-saving levers. The head and neck are the most typical balance lever principle. The hand holding a heavy object is the speed lever principle. When a person is standing, the center of gravity of the human body is generally located about 7 cm in front of the second sacral vertebra; but also standing, if the arms are raised above the head, the center of gravity will rise accordingly; and the center of gravity of the human body is also subject to the constraints of gender, age, and body structure characteristics. For example, when standing, women’s center of gravity is generally at 55% of height, while men’s center of gravity is about 56%-57% of height, children because their heads and torsos are heavier, the center of gravity position than the adult high upper limb gymnasts than the lower limb of soccer players with a high center of gravity position. The higher the center of gravity of the human body, the less stable it is. The normal human spine is divided into five parts: the cervical, thoracic, lumbar, sacral and caudal vertebrae. There are 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 5 sacral vertebrae, and 4 caudal vertebrae, for a total of 33 vertebrae. In adulthood, the five sacral vertebrae grow together to become the sacrum, and the four caudal vertebrae fuse with each other to become the coccyx. Therefore, only 26 vertebrae can actually move. They are surrounded by muscles, ligaments and joint capsules to form a movable central axis with strong support, which protects the spinal cord, maintains body movement, and transmits the load of the head, neck and trunk to the pelvis. There are intervertebral discs between the vertebrae and the vertebrae, but there are no intervertebral discs between the cervical, cardinal, sacral and caudal vertebrae, so there are only 23 intervertebral discs throughout the body. The intervertebral discs are located between two vertebral bodies. The discs in the lumbar region are the thickest, at about 9 mm. The discs are the most heavily loaded part of the body. After a person reaches the age of 20, the lumbar disc begins to degenerate, the water content in the nucleus pulposus gradually decreases, accompanied by dehydration of the nucleus pulposus, reduced tension of the nucleus pulposus, and thinning of the disc, while the proteoglycan content of the nucleus pulposus decreases, collagen fibers increase, and the nucleus pulposus loses elasticity. Therefore, as the structure of the lumbar intervertebral disc ages, its elasticity and resistance to load also decreases with age. In fact, the disc is an elastic container filled with fluid, and when the spine moves, the main change in the disc is the flow of fluid within the container, which deforms the disc, but not compresses it, so that the pressure transmitted by the vertebral body can be evenly distributed. The spine is not a straight line when normal; it has three curves: anterior cervical convexity, posterior thoracic convexity, and anterior lumbar convexity. These three curves meet at the center line of gravity to keep the body in balance. (The human body can bend and rotate back and forth, relying mainly on the spine.) If these physiological curves change or straighten, it will produce physical discomfort or low back pain. The mobility varies by location, with the cervical spine being the most mobile, the thoracic spine being the least mobile, and the lumbar spine being somewhere in between. Osteoarthrosis of the spine is most common in the cervical and lumbar spine. Most cervical spondylosis starts slowly, with only neck discomfort at the beginning, followed gradually by radiating pain in the upper limbs, vertigo in a few patients, and even muscle strength loss and muscle atrophy in severe cases. Low back pain in lumbar spine osteoarthropathy is characterized by heavy pain when the position is suddenly changed from the resting state, and the pain is reduced after a period of activity, but it is aggravated again when there is too much activity. Similarly, when you wake up in the morning, you will feel a sense of lumbar stiffness and pain, which can be relieved after getting up and moving around. Osteoarthritis prevention and control In order to prevent the occurrence of osteoarthritis, we should have a correct posture in our daily life, whether standing or sitting, such as keeping the lower back flat to avoid excessive convexity of the waist; when sitting, it is best to choose a hard chair, and the height is appropriate, because when the chair is too high, so that the feet are off the ground, the muscles in the back of the thighs are pressed, affecting the relaxation of the pelvis, too low, it will increase the hip joint flexion, so that the pelvis tilted forward. These are prone to cause lumbar muscle strain. Also should pay attention to the waist and the back of the chair to stick, the best part of the stick in the upper lumbar spine, that is, about 20 cm from the sitting board. Sitting in this way, not only feel comfortable, but also to protect the lumbar muscles. Long-term in a fixed sitting position, the lower extremities should maintain a certain degree of flexion, if the lower extremities are not straight, so that the muscles of the back of the calf tension, pulling the pelvis, lumbar lordosis increased, easy to cause labor stirring for people who need to work for a long time half-bending (cooks, hairdressers), should keep the lower back flat, so that gravity falls at the hip joint, so that it is not easy to fatigue. Most elderly people have been injured in the lower back, when standing, it is necessary to take turns to pad a wooden stool under one side of the foot, so that one side of the hip and knee joint slightly flexed to reduce pain. When bending to get something, do not be afraid of trouble, be sure to use the posture of flexion and extension, that is, the first hip and knee flexion, so that the muscles of the back of the calf relax, the waist straight, which can reduce the weight of the lumbar back muscles.