How much should i increase running per week?

The rule of thumb is about 10% more per week. If you were to run 10 miles in one week, the next week shoot for 11. I don't know about your knees, try new shoes or maybe insoles. Be sure to properly stretch and warmup before running. :)

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Take notice of your shoes, is the sole of them cushioned enough for the amount of running you're doing? you can have your strides and foot planting tested at a local sports shop. This is probably the cause of the bad knees. A doctor can also prescribe you with in-soles to help.

I wouldn't increase the amount at all, at the minute anyway. Until you can run comfortably with no pain, then move up.

Good advice so far.

Would just add, do 3 weeks at any level of effort ie duration, pace, incline etc

If third week feels more manageable then raise the level and so on.

Don't raise all three in the same week!!!!