Is running bad for your knees?

Depends: A good running stride is key. That being said the elliptical is lessthan impact for sure. I think it is hard to get into any good shape on machines..Run a 6 min mile on the road and tell me your heart rate is the same as the treadmill...As an example.

It sure CAN be...: If you are concerned about the effects of running on your knees, the most important factor is heel strike cushioning. My favorite insole is the spenco polysorb cross-trainer replacement insole. http://www.spenco.com/products/footcare/poly-sorb/cross-trainer.

Depends: On the state of your knees and also your running biomechanics. There are some people who can run, significant mileage >20-30 mi/week, well into old age and others who develop progressive degenerative changes in the late 30s-40s related to the wear and tear of running on their knees. Listen to your body and consider an formal consultation with a running clinic to optimize your biomechanics/shoes

Could be.: While running is great for your cardiovascular and pulmonary systems, it can be rough on the joints - knees, ankles and hips. The key is to work to perfect your running stride, stay as horizontal as possible while running, try not to bounce up and down, and stride heel-to-toe.