On Sunday morning, nearly 60,000 runners tackled the London Marathon, pushing their bodies through extreme and, in many cases, unprecedented physical strain. Countless participants will have been nursing blisters, battling cramp or gritting their teeth through pain well before they even glimpsed the finish line on The Mall, 26.2 miles later. Experts say it's around mile eighteen that joints which held up well during training begin to voice their complaints, with the knees, feet and hips in