Waking up with knee pain can be caused by overwork, rheumatoid arthritis and meniscus injury. 1. Overwork: If you work too much or do strenuous exercise before going to bed, it may cause the muscles in the knee joint to be in a state of fatigue, resulting in the accumulation of metabolic products, stimulating the peripheral nerves and thus waking up with knee pain. 2. Rheumatoid arthritis: patients who suffer from rheumatoid arthritis may lead to knee pain, swelling and other symptoms. If the patient is stimulated by cold after waking up, he will wake up with knee pain. 3. Meniscus injury: if the patient suffers from meniscus injury, after waking up activities may aggravate the extrusion of the meniscus, thus waking up knee pain. If the waking knee pain is caused by overwork, it can be improved by proper rest, but if it occurs for a long time, it should be examined and treated by a doctor in time.