Leg weakness, also known as lower limb weakness, can be caused by a variety of reasons: 1, intervertebral disease: can cause lower limb weakness, such as cervical spondylosis, cervical spondylosis not only has symptoms of the upper limbs, neck symptoms, but also can appear symptoms of the lower limbs, especially spinal cervical spondylosis, that is, cervical disc herniation or bone spurs, a variety of reasons lead to compression of the spinal cord caused by spinal cervical spondylosis, can appear lower limbs Weakness, a feeling of stepping on cotton, and unstable walking; 2. Knee problems: patellar chondromalacia can cause weakness of the knee joint, especially when going up and down stairs; 3. Hypokalemia: it can cause weakness of the lower legs and thighs, but it can mainly be accompanied by weakness of the whole body and muscle weakness, which is a significant feature of hypokalemia; 4. Osteoporosis: it can also cause weakness of the lower limbs.