I started running about 3 weeks ago (3 x a week) in an effort to get in better shape and lose weight. I have noticed my stamina improving but my joints still hurt (knees & ankles) after I run. I am running about 4 miles each time I go out. I currently mix in some walking with the running too.

Is there any particular technique or way to run (like heel-toe or on the balls of your feet, knees bent more/less?) that would lessen the impact on these joins or do I just need to tough it out until I've lost enough weight to where the joint pain isn't as great? Currently I can run about a mile and a half before the pain around my knees is enough to make me want to stop and walk for about a quarter-mile before starting to run again.