Good question, Stacy! I think that some short hiit training sessions 2x/week will help complement your running sessions (running perhaps 2x/week?). I found that the conditioning I've done with Cathe transferred to my running. I was glad to read in a recent Cathe post that research supports this:
http://cathe.com/much-cardio-need
My suggestion for a weekly routine:
- a total body weight workout one day
- run 2 days/week (perhaps with core training after your run)
- 2 days with short hiit segments along with weights - 1 day upper body and 1 day lower body
(this could be substituted with upper body circuit and lower body circuit so you get the cardio and weights in one)
I would alternate the running and the hiit days so you don't run on two consecutive days. Hopefully this will be easier on your knees.
You may prefer to choose Cathe's low impact hiit workouts (rather than high impact) to also protect your knees. I find Cathe's spin workouts to also be largely intervals and so may be a good non-impact alternative for those days.
I wear a heart rate monitor while running to ensure I am staying within my target heart rate range. I don't worry too much about my speed as long as I am working out safely within my range. As I gradually get in better shape I can go faster while maintaining the same heart rate range.
Hope others respond too and suggest some alternate ideas.