The knee, the largest and most complex joint in the human body, is a hinge joint, and it is one of the few joints in our body that can only move in one direction. The knee is the largest weight-bearing joint in the human body The knee is also the largest weight-bearing joint in the human body, and a normal human knee can carry an average of 35 kg. The more weight you carry, the greater the chance of wear and tear on the joint cartilage, and the tendons are prone to injury, resulting in faster degeneration of the knee joint. The weight-bearing multiples of the knee are as follows: 1. When lying down, the weight-bearing of the knee is almost zero. 2. When standing up and walking, the weight-bearing of the knee is about 1 to 2 times the weight. 3.When going up and down slopes or up and down steps, it is about 3 to 4 times. 4.When running, it is about 4 times. 5.When playing ball, it is about 6 times. 6.When squatting and kneeling, it is about 8 times. For example: a person weighing 50kg, for each step, the knee has to bear about 200kg of weight. (50*4 times) Knee quality has the best condition for 15 years Before the age of 15 The knee joint is in the developmental stage, and most of the growing pains in adolescence occur near the knee joint. Between the ages of 15 and 30, the knee joint is in “perfect condition” and works tirelessly. As long as the knee joint tissue is not damaged, its presence is basically not felt. Between the ages of 30 and 40, the patellofemoral cartilage undergoes early and mild wear and tear, resulting in a period of weakness and short-term knee pain that lasts from a few weeks to a few months and is not even noticeable to some people. Patellofemoral cartilage is a 3-5 mm thick layer of hyaline cartilage in the human knee joint that provides a cushion for the knee joint. However, because the patellar cartilage has no nerve distribution, it will only sound an “early warning signal” once during the vulnerable period before the full layer wears out, and strenuous exercise should be avoided during this period. From this time onwards, the knee joint can no longer be used as you wish. Between the ages of 40 and 50, the inside of the knee joint is prone to soreness after walking long distances, which is relieved by gentle hand rubbing. Since 60% of the body weight is supported by the medial side of the knee joint, degeneration of the medial meniscus occurs earlier. Because there are nerves in the meniscus, the pain can be felt during the degeneration process. This is a reminder that it is time to start taking care of your joints. Over the age of 50, the knee joint will feel significant pain because the patellar cartilage has reached the end of its “useful life”, the cartilage is worn down and arthritis has developed. This is the time to conserve the use of the joint, reduce strenuous exercise, especially stairs and climbing, and use crutches if necessary to reduce the stress on the knee joint. Causes of knee pain in middle-aged and elderly people after middle age, the tendons and ligaments of the knee joint begin to degenerate, the synovial fluid secretion in the joint cavity decreases, the bone surface of the joint rubs together for a long time to form bone wear, and the tissue around the joint is prone to fibrous adhesions due to inflammation, so the elderly often feel stiffness in the knee joint. This is why the elderly often feel stiffness in their knee joints. When they move, they will make a “clicking” sound or frictional sound, and when they are cold or overly active, they will experience pain, swelling, and fluid accumulation in the joint cavity, and in severe cases, they will have deformed joints and become disabled. Specifically, the causes of knee pain in the elderly are as follows: 1. Chronic synovitis: Chronic pain and swelling in the knee joint. Synovial effusion and synovial hypertrophy can be seen on physical examination. 2. Patellar deviation: The knee joint is sore and weak after activity, improves after rest, and is painful when semi-squatting. 3, free body in the knee joint: the patient’s leg is weak or has a feeling of joint jamming, and there is a friction sound under the patella. 4, prepatellar bursitis: history of trauma, causing prepatellar pain, localized pressure pain on physical examination. 5, osteoarthrosis: after sitting or squatting for a long time, when standing up, going up and down the stairs, joint pain is obvious, relieved after rest. 6, pseudogout: more male patients, mainly in the knee joint. X-rays show calcification of meniscus and articular cartilage surface. 7, femoral head necrosis: hip lesions have knee pain symptoms. Knee health training Through appropriate muscle strength, stability training can play a preventive health effect on the knee: 1, side lying exercises left side lying, knees slightly bent, heels together. Head resting on the left arm, eyes looking straight ahead. The right hand holds a weight of about 1 to 2 kg and places it on the outside of the leg. Then tense the abdomen, tense the hips, lift the knee of the right leg as high as possible, hold the body still while lifting the leg, hold for a few seconds and put it down. Repeat the exercise 15 times, change legs. 2, leg lifting exercises stand behind a solid bench or steps, right foot on (heel do not overhang), and focus the weight on the right foot, the body is raised, the left foot toes touch the step, hold on 1 to 5 seconds. Then lower the left foot and tap the ground. Repeat 8 to 10 times, change legs. 3.Bridge exercise Lie flat on the ground, knees bent, feet apart, hip-width apart, arms on the sides. Slowly lift the hips and leave the ground smoothly. Then slowly lower. Repeat 15 times. 4, leg extension exercise lying flat, knees bent, feet flat on the ground. Extend the left leg, set into the stretching, pulling belt or towel, hands grasp the ends of the pulling belt. Use the strap to pull the leg to the chest, and then force the calf straight, hold for 10 to 30 seconds to exercise the calf muscles and hamstrings. Repeat the action 3 to 5 times, then switch legs.