Running places 3-4 your bodyweight through each leg and is therefore a high impact exercise. How and where the loads are absorbed within the body are determined by your running form and technique. Key factors are where you land on the foot and where the foot lands in relation to the body. It is also important that you strengthen your core musculature in line with your running. Check out www.rehabyourinjury.com for videos on core conditioning and running technique.