Morton’s neuroma is an overuse injury where the intermetatarsal nerve (lying between the metatarsal bones in the ball of the foot) becomes inflamed or enlarged. The symptoms include pain or burning under the ball of the foot, with numbness, tingling, or burning extending to two toes (usually the third and fourth toes). This problem doesn’t occur overnight but may be lingering from the prerace training period. However, the marathon can aggravate the condition, producing a flare of symptoms. The distance of the marathon, narrower than usual or tightly laced racing shoes, and the downhill running at Boston can all be aggravating factors. If you should acquire Morton’s neuroma, consider new shoes, taking care to properly fit the width of your foot. You may also consider replacing the insoles of your running shoes with superior, well-padded over-the-counter insoles. Also avoid narrow shoes in your non-running footwear.