For the causes of foot weakness and tenderness, they are as follows: 1, spinal cord type cervical spondylosis: cervical discs can compress the spinal cord, which can cause lower limb muscle weakness, resulting in lower limb coordination decline, manifested as unstable walking, leg tenderness, a feeling of stepping on cotton when walking, and easy to fall. 2, water-electrolyte balance disorders: for example, when low potassium, there will be a state of general weakness, also including foot and leg weakness or 3, lumbar disc protrusion: cause sciatic nerve compression, when the protruding disc compresses the nerve more seriously, it will not only cause radioactive pain and numbness in the lower limbs, but also make the muscle strength of the lower limbs diminish, feeling weak and tender in the feet.