Knee pain

Hello Dr.

4 years ago at the age of 26 I trained 5 months for a marathon.   One day the training reached 20 miles in a session.  Immediately after running my right knee became very sore and swelled.

I took the next two weeks off and ran the marathon.  After the marathon the same outcome with my right knee occurred.

Over the next 5 years I have kept my mileage down to 3 miles per day just a couple times each week, taken up to 7 months off, but after each run my knee has these symptoms.
- Behind the knee cap feels achy/pain
- The pain goes away overnight and feels better the next morning
- Possibly a little swelling when I run around 10 miles in one session.

Any thoughts on what might be causing this?  
Do I risk ruining my knee if I keep running?

Best regards,
P.S. I have tried various running shoes, techniques, no pavement running, but no luck yet.

[Abhijeet Ghosh]

Dear Friend,
It appears that you have sustained injury to the meniscus of the knee.
Please get a MRI scan done for the same, and post the scan results are available, we can plan the treatment further.
Meanwhile before the scanning is done, your knee should not be inflamed. Hence ensure that, before the scans are done, your knee is in resting condition, else we will not be able to view the knee joint properly.
Also during swelling, do wear a stretchable 15 cm crape bandage.
Feel free to discuss further.
Regards.