The common causes of thigh weakness and weakness are as follows: First, lumbar disc herniation and severe lumbar spinal stenosis can lead to nerve compression in the lower extremities, thus causing motor dysfunction, thigh weakness and weakness, and fatigue can easily occur when the patient walks. The location of the lumbar spine lesion and the degree of nerve compression can be found through CT scan or MRI. Second, sciatic neuropathy, such as pear-shaped muscle syndrome or viral sciatica, can lead to sciatic nerve motor conduction dysfunction, the sciatic nerve innervates the thighs and calf muscles, the patient will appear weakness in the thighs, weakness, but also a sense of discharge of the lower limbs. The above two causes are common causes of thigh tenderness and weakness. Through specific auxiliary examinations and clinical examination, the cause can be diagnosed and early treatment can enable the patient to recover as soon as possible.