Patients always feel weakness in their legs, and the following causes are common: 1. Severe atrophy of lower limb muscles: generally seen in prolonged fixation, such as fracture dislocation, but also in severe knee osteoarthritis, ankle osteoarthritis, and femoral head ischemia and necrosis, all of which can lead to clinical symptoms of weakness due to atrophy of leg muscles. 2. Lumbar spine lesions: such as herniated disc, spinal stenosis, lumbar spine Slip disorders, etc., can stimulate the compression of nerves, resulting in the loss of innervation of the lower limb muscles, and the leg muscle strength will be significantly weakened, and the patient can even develop intermittent claudication, walking difficulties, and cannot participate in normal sports. The lesion can be clarified by MRI, X-ray examination and electromyography of the lower limbs. Early diagnosis and early treatment are extremely beneficial for the recovery of leg muscle strength. Usually, attention should be paid to protecting the joints of the lower back and the whole body to avoid serious lesions of the joints of the lower limbs and lumbar spine lesions.