Well, lots of reasons. But having mobile hips will essentially reduce the amount of pressure placed on the knees and back. The majority of people sit down everyday in their normal jobs and this can cause the muscles of the hips to tighten up and the glute muscles to become weak and inactive. This is caused by the the 90 degree leg position when sitting down that causes the hip flexors to continuously contract. In return the antagonistic (or opposite) muscles which are the glutes relax. This is why I recommend using a standing work station where possible-
|Standing work station to reduce back/hip pain|
There are hundreds and hundreds of stretching and rolling techniques that you can use to improve mobility but here are a few that Ive been using recently and are recommended by http://www.defrancostraining.com/
1.Foam Roll the IT band (outside of thigh) -10-20 rolls - focus on tight spots
2. Foam Roll the adductors (inner thigh)-10-20 rolls- pay attention to tight areas
3.Glute/piriformis myofascial release (bum roll) - 1 minute each bum - feel the pain and repeat
4.Fire hydrant circles- 10 in each direction and each leg
5.Mountain Climbers - 20 repetitions
6. Hip Flexor Stretch- 30 seconds hold each side
For more detail about each of the stretches - http://www.defrancostraining.com/ask_joe/archives/ask_joe_08-10-03.html
The only bit of equipment you need to perform all of these stretches is a tennis ball (as you can use a tennis ball instead of a foam roller).
Perform this routine 5-7 times a week which won't take much time out of your day and will improve your lower body mobility and how you move by leaps and bounds!