I would say tendonitis, plantar fasciitis, and heel spurs are very frequent problem which runners suffer from. Due to limited time of this discussion I will focus on tendonitis as this is a painful condition that often frustrates many athletes because it tends to prevent them from being able to enjoy their activity and makes it difficult to maintain their fitness.
I would say by far the two biggest problems I see are:
Ingrown toenails and Planter Fasciitis (heel pain, heel spur). In this interview I will discuss ingrown nails and will discuss heel pain in next interview due to limited time.
An ingrown nail occurs when the toenail is pushing on or digging into the skin at the side or end of the toe. It typically starts as a mild redness, inflammation, or mild pain. Usually it will get worse with time and can become infected. If left untreated, in can progress into an abscess, infection, and in rare occasions serious bone infection requiring surgery. It is critical to get the nail evaluated as soon as possible to prevent complications.
A bunion is an abnormal shifting of the bones in the foot which causes a bone bump on the inside of the foot and the big toe tends to deviate toward the 2nd toe. The big toe is critical to walking and when it is misaligned it can cause pain in the foot and other joints due to walking abnormally. With the change in size and position of the foot from a bunion it can be hard to find shoes that fit. The good news is it can be fixed. You don’t have to hobble the rest of your life.