BACKGROUND: Unlike structural imaging such as MRI and CT, infrared thermography reflects functional imaging of autonomic function involvement and disorders of sympathetic vascular tone. Neuromuscular disorders require an objective evaluation of autonomic function. This study investigates the skin temperature of the lower extremities in patients with lower back pain and evaluates the relationship between the degree of pain and lower extremity temperature abnormalities. DATA AND METHODS: The study population consisted of 65 patients with lower back pain, including 21 cases of simple low back pain, 42 cases of low back pain accompanied by pain in the lower extremities but not the knees, and 20 cases of normal subjects in the control group. Infrared thermograms were used to determine the temperature of different areas of the lower limbs and the temperature difference between the right and left sides of the healthy and affected side or normal people, and the pain level was expressed by VAS score. RESULTS: Lower back pain was closely correlated with the temperature difference between the plantar aspect of the lower extremities (r=0.502), which was statistically different compared to the control group. The temperature in the remaining locations was not statistically different compared to the control group. DISCUSSION: The close correlation between lower back pain and temperature differences in the plantar aspect of the lower extremities may be related to the following mechanisms: patients with lower back pain may be accompanied by damage to the L5 and S1 nerve roots, and the temperature region of the damage to the nerves is superimposed exactly on the plantar aspect of the foot; changes in the peripheral vasculature are more directly reflected ventrally; and the distribution of body weight in patients with lower back pain influences the infrared thermal radiation of the plantar aspect of the foot. CONCLUSION: The determination of lower extremity temperature may be one of the effective methods to reflect sympathetic dysfunction in patients with lower back pain. The determination of plantar infrared thermogram temperature reflects the severity of lumbar spine problems. The more severe the lower back pain, the greater the difference in temperature of the affected plantar side.