A gait analysis is very useful in determining muscular-skeletal problems that can create joint injury. For example, problems with the feet can cause problems in the knee, hip, or lower back. Merely treating the knee, hip, or back will not resolve the problem.
For proper treatment it is necessary to know the underlying cause. This is where a gait or running analysis would be very important. It can help identify poor mechanics that may be creating the problems or a joint action that can create problems in other areas.
To get an accurate gait analysis, however, you must go to someone who is specialized in this area. This is usually easier said than done. For example, the analysis should be of your running on the track and not on a treadmill because treadmill technique is different from road technique. Also, very few people are truly qualified in analyzing technique.
Because someone is or was a runner and may be a sports medicine doctor does not mean that he understands technique. This is a subject that must be studied and learned. And it should be noted, that this is not done in any formal course of study. Thus it is important that you seek out someone who is truly specialized in this area.
See Explosive Running for more information.