The causes of knee pain when squatting down and standing up may include: infectious factors, acute and chronic injuries, degenerative factors, autoimmune diseases, tumors of the bone and joints, and metabolic bone diseases. 1. Infectious factors: if the disinfection of knee puncture is not standardized, it will cause infection in the joint, or soft tissue inflammation, osteomyelitis adjacent to the joint, abscess and so on, which will cause the symptoms of knee pain when squatting down. 2. Acute and chronic injuries: such as meniscus injury, cartilage injury, dislocation, ligament injury, fracture and other reasons can cause knee pain when squatting down and standing up. 3. Degenerative factors: knee joint hyperplasia can cause knee osteoarthritis to appear squatting up knee pain. 4. autoimmune diseases: rheumatoid joints can also cause knee pain, and then squatting up to cause knee pain. 5. Bone and joint tumors: such as osteoblastoma, osteochondroma can also lead to knee pain when squatting and standing up. 6. Metabolic bone disease: such as gouty arthritis, vitamin D metabolism disorders, etc., will cause patients to squat up when the knee pain. It is recommended that patients actively consult the doctor to clarify the cause of the disease after treatment.