If thigh muscle weakness is caused by trauma or excessive activity, functional exercise is required. You can consult a specialist or rehabilitation physician for effective passive activity exercise and guided active activity exercise. The key to passive activity exercise is position change, such as knee extension, after which the quadriceps strength will be exercised. Alternatively, the patient can lie in bed with the straight leg elevated and the entire leg raised for quadriceps strength training, which is also active training. Passive training is often done by having the patient lie prone on an examination bed and perform prone knee flexion. CPM machines are also available in hospital wards for exercise, and CPM machines are machines that perform functional exercises for hip flexion and knee flexion. If thigh muscle weakness is caused by lumbar spine disease, such as lumbar disc herniation or lumbar spinal stenosis, you need to treat the cause of the lumbar spine condition, and the soreness and weakness can be relieved only after the cause is improved.