A squat and then stand up when the knee pain occurs for the following reasons: 1, caused by knee arthritis, knee arthritis attacks often appear joint fluid, joint swelling and other phenomena, this situation will compress the surrounding tissue nerves, there will be pain. Once the joint is squeezed hard when a person stands up, it can cause the pressure to rise and can make the pain worse. In addition, for some older people, it is often osteoarthritis, which can cause joint pain during exercise even if there is no fluid in the joint cavity.2. Caused by calcium deficiency, calcium deficiency can lead to joint degeneration and pain, which can cause knee pain when standing up and exerting force.3. Caused by trauma, when the knee joint is sprained, bruised, and other traumatic injuries, it can Damage to the muscles around the joint, when standing up, the muscles will appear painful when exerting force.