Sitting for a long time and feeling knee pain, clinically common causes are muscle spasm, osteoarthritis of the knee, lumbar disc herniation and so on. 1. Muscle spasm: for normal people, long time to keep sitting and standing position, the muscles around the knee joint are easy to be in a state of tension, fatigue and so on, which will cause muscle spasm, thus leading to pain symptoms around the knee joint. 2. Osteoarthritis of the knee: this condition refers to a chronic joint disease characterized by degenerative cartilage lesions and secondary osteophytes of the knee, this disease progresses slowly, and with the passage of time there will be symptoms such as knee pain, stiffness, swelling, deformity and so on, and sedentary status will aggravate the condition. 3. Lumbar disc herniation: this disease is a common and frequent disease in spinal surgery, or the most common cause of lumbar leg pain and lower back pain. People with the disease have degeneration of the lumbar intervertebral discs and damage to the annulus fibrosus, and the nucleus pulposus protrudes to the nerve root, cauda equina and other stimuli, with clinical manifestations of lumbar pain, sciatica, cauda equina syndrome, and numbness of the lower limbs. Sedentary state will aggravate the related symptoms, and the knee area will also have obvious numbness, pain and other symptoms. If the above conditions exist and the pain symptoms are not relieved, it is recommended to go to the orthopedic department of the hospital for consultation and treatment.