Since sustaining an ITB injury and a long subsequent healing process, I have become super conscious of my hill running. I live on top of a plateau of sorts and so virtually every run I start from my home involves a significant up and down hill effort. ITB is particularly suscpetible to re-injury on hills and I have become particularly conscious of my form on graded terrain-particularly on the downhill which puts increasing stress on the knees and connective tissue.
Here's a guideline for proper form when taking hills on the down side.
There's no single best way to get down hills, safely and with a maintenance of speed. Shallow hills are really not a problem, but on steeper grades it is easy to lose control and waste your effort. If you like to run trails as I do, it's really important to maintain your form - and with a little conscious effort it will become very natural to you.
1) Body Position
At the start of a downward grade, tile you body forward from the waist. Consciously maintain a position in which your trunk maintains perpendicular to the ground, (the angle of your body therefore depends on the steepness of the grade.
2) Maintain Control
Once you've assumed the proper body position, your speed will increase naturally. To deal with this, raise your knees and increase the length of each stride.
3)Maintain Balance
Allow your elbows to rise up and away from your body The motion here is much like a tightrop walker using a pole for balance.
4) Reduce Impact
Descending a hill will force more shock through your feel, shins and knees. To cushion the shock focus on landing on the forefoot, rather than on your heels.
To get the most of the speed advantage on the downhill, practice taking the upside holding back a little so that you are not exhausted by the time you reach the top. This will enable you to run faster on the downside.