Out of the blue, I am experiencing intense, sharp pain in the middle of my heel, radiating upwards about 2 cm. It is intermittent, and excruciating when it happens. It lasts for about 10 to 15 seconds, then ceases. I haven t put any excess load on my heel recently, and my foot is in excellent shape. It has woken me in the night, and nothing seems to alleviate the pain when it occurs. I am 60 years old, in good health. Any advice would be most appreciated. Thank you.