A degenerative tear of the meniscus

Given the data you provided (pain in the knee that appeared after 2½ miles on a treadmill and increases when you push on a specific area, previously diagnosed “fraying” meniscus and mild arthritis), you might be experiencing degenerative tear of the meniscus. Meniscus is a fibrocartilage strip in the knee that helps the joint to function properly. During excessive use of the knee, the menisci might be damaged. In younger people, acute damage of the menisci might be seen, whereas in older people the chronic damage to the menisci might lead to degenerative tear. In both cases, the tissue of the meniscus is damaged and needs further treatment.

The dominant symptoms include pain and/or swelling in the knee. Usually when the knee is not loaded with weight, the pain disappears or is at least less in intensity.

You might want to visit an orthopedist for a physical examination. Several signs might help the orthopedist. S/he might additionally recommend arthroscopy which is a procedure in which the interior part of the knee is seen through very small holes. If degenerative tear is diagnosed, surgical treatment might be recommended.

As far as the prognosis, the doctors would determine whether you are allowed to have a treadmill run in the distant future, but it is definite that would you have to go under physical therapy and would need a long time period before bringing yourself to the previous physical activities which include using your knee.