The causes of left foot weakness are commonly found in the following: First, cervical spondylosis: especially spinal cervical spondylosis, when the protruding cervical intervertebral discs compress the spinal cord, there is often a decrease in lower limb strength, and there can also be a decrease in lower limb coordination, which can lead to lower limb weakness, unstable walking, and a feeling like stepping on cotton. Second, lumbar spinal stenosis: intermittent claudication often occurs, which can be manifested as radioactive pain in one lower limb and reduced strength of the lower limb. Third, lumbar disc herniation: when the herniated disc tissue compresses the nerve roots on the left side, it will cause radioactive pain in the left lower limb, and when the nerve roots are obviously compressed, there will even be a loss of strength in the lower limb.