Yoga postures are many times taught starting on the right side of the body. By doing so, you are actually creating an imbalance you may not be aware of.
Most people are weaker on the left side, as most people are right-handed. But when we practice yoga asana starting on the right, we can actually create more problems.
I'll give an obvious example. If you take your right foot into lotus pose first (although there are good reasons for doing this), the next leg you place in lotus, over the other leg, is at a distinct disadvantage. You have to lift the leg over the other without being able to protect the knee.
The left knee is weakened, adding to an already weak side.
When we practice yoga starting on the right side, we not only strengthen the already dominant right side of the body, but we spend less time on the left. We do this unconsciously. This is more especially the case in a time restricted, class environment.
The solution? Simply start with your left for strength building poses, and spend longer here than the right. If the right is already stronger, then you can start with the right side when opening the body through more passive stretches, spending less time opening the left, weaker side.
This way, you strengthen the weaker side, and open the stronger side.