The left leg is heavy and the right leg is not easy to consider lumbar disc herniation, lower extremity venous thrombosis, cervical spondylosis, lumbar spinal stenosis, lumbar spondylolisthesis, spinal tumors and so on. 1. Lumbar disc herniation: if the nucleus pulposus protrudes to one side and compresses the nerve root on one side, there can be pain, heaviness and numbness in one side of the lower limb, and the other leg usually does not have a heavy feeling. The other leg usually has no heavy feeling. The diagnosis can be made clearly through lumbar MRI film. 2. Lower extremity venous thrombosis: Lower extremity venous thrombosis can be easily formed by lying in bed for a long time after lower extremity surgery, which is manifested as heaviness of one side of the lower extremity and swelling of the lower extremity, and it can be diagnosed clearly through the ultrasound of lower extremity blood vessels. 3. Cervical spondylosis: spinal cervical spondylosis can cause heaviness of the lower limbs, limping and easy to fall. 4. Lumbar spinal stenosis: osteophytes or hypertrophy of ligamentum flavum compresses the spinal cord, resulting in lower limb weakness, heaviness, and claudication. 5. Lumbar spondylolisthesis: lumbar instability compresses the spinal cord, resulting in heaviness in the left leg. 6. Spinal tumor: vertebral body tumor, bone destruction and compression of spinal cord and nerves may appear heavy legs, and radiographs can be used to make a clear diagnosis. There are many reasons why the heavy left leg is not as easy as the right leg, if it does not get better or further aggravated by resting, it is better to go to the hospital for checking, and follow the doctor’s instruction after clear diagnosis.