The possible clinical causes of knee muscle pain include excessive exercise, soft tissue injury, osteoarthritis, rheumatoid arthritis and so on. 1. Excessive exercise: Excessive exercise of the lower limbs can cause the accumulation of lactic acid in the local muscles, causing symptoms of knee muscle pain, which is generally physiological and can be relieved after rest. 2. Soft tissue injury: this condition is usually associated with chronic strain, fall, contusion and other factors in the knee joint area, the injury site will appear localized blood seepage, edema, pain and other symptoms, some people in the recovery process will also appear in the knee muscle pain symptoms. 3. Osteoarthropathy: this condition is usually associated with advanced age, overwork, obesity and other factors, the patella and other bone tissues will be damaged, and thus manifested as knee pain, swelling, stiffness, restricted movement and other symptoms. 4. Rheumatoid arthritis: this condition is usually associated with autoimmune, genetic, infection and other factors, and its main features include joint involvement pain, morning stiffness, joint deformity and so on. There are other causes of knee muscle pain, such as lumbar intervertebral disc herniation, etc., if rest does not relieve, it is recommended to go to the hospital in a timely manner to improve the relevant examinations, a clear diagnosis, and then follow the doctor’s instructions for targeted treatment, so as to avoid delays in the condition.