Numbness of the left heel can be caused by bone spurs, Achilles tendonitis, aseptic fat pad inflammation, insufficient local blood supply, lumbar disc herniation and other conditions. 1. Bone spurs: with the increase of age, the bone of the left heel will occur osteophytes and bone spurs, bone spurs can compress the nerves and cause numbness of the left heel. 2. Achilles tendonitis: long-term foot activities, such as running, jumping, walking and other actions, can lead to the Achilles bone and the Achilles tendon of the foot for a long time by the tension, the local inflammation can occur, the stimulation of inflammation can cause numbness of the left heel symptoms. 3. Aseptic fat pad inflammation: long-term over-activity, gravity pressure or excessive pulling of the fat pad under the left heel can lead to aseptic inflammation of the heel, which can cause numbness in the heel when it is cold or over-activity. 4. Insufficient local blood supply: prolonged sitting, standing and squatting can lead to the foot to maintain the same position for a long time, can be due to gravity compression resulting in poor blood supply to the heel and numbness symptoms. Lower limb vascular disease and diabetes can also be due to poor blood circulation, resulting in local ischemia and numbness symptoms. 5. Lumbar disc herniation: Lumbar disc herniation can compress the nerve root, which can lead to numbness and discomfort in the heel and other innervated areas, such as nerve compression symptoms. There may also be other reasons, when there is numbness on the outside of the left heel, you need to consult a doctor in time, under the guidance of specialists to actively carry out appropriate treatment, which will help to alleviate numbness and other uncomfortable symptoms as soon as possible.