I run 15-20 miles/week and lately have had horrible inner calf pain that radiates from ankle to knee, what is this?

Overuse injury maybe. You may be suffering from the initial stages of an overuse injury. If you have pain along the tibial (shin) bone, you need to be examined by your trainer, therapist or physician. Try decreasing the mileage or intensity of your regimen for a week or two by limiting the impact aerobic exercise (running, jumping, etc.). Your response to this training change will help your examiner formulate a tx plan.
Many possibilities.. This could be many things and i would recommend seeking complete medical evaluation to get an accurate diagnosis. Common causes of these symptoms can be shin splints, medial tibial stress syndrome, periostitis, stress reaction or stress fracture, or exercise-induced compartment syndrome.

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Severe knee pain for 12 days. Calf pain and ankle pain. Feels like water running in ankle. Stiff ankle and acl. Can't rest heel without pain.

See your doctor. There are different possible causes for knee, calf and ankle pain. The most worrisome would be a blood clot. Would recommend an evaluation with your physician or local orthopaedic surgeon to identify the cause and recommend treatment. Read more...
I assume you visited. An orthopedist yes? If you haven't, now would be a good time. Read more...