The lack of sensation in the thigh may be caused by the following reasons: 1. lesions related to the lumbar spine, such as lumbar intervertebral disc herniation or lumbar vertebral spinal canal occupying lesions, which can cause the stimulation of the relevant nerve roots, and then a complete loss of sensory function in a certain place of the thigh; 2. peripheral nerve compression, such as lateral femoral cortical nerves or femoral nerves can lead to limited sensory dysfunction in a certain place of the thigh if the femoral nerve is stimulated by the compression; 3. The skin lesions here, such as burns, frostbite or chemical damage, can cause superficial sensory nerve endings to be damaged, followed by numbness; 4, old injuries, such as the thigh in the past there is a serious soft tissue blunt contusion, which left this symptom.