Most people have a small leg length discrepancy, most often something they were born with. The difference is usually very small, around 2 centimeters, and doesn't cause problems. However, once you have a larger leg length discrepancy, which can be caused by a broken leg bone, including a femur, you can develop a slew of injuries.
If your femur heals wrong, there's a chance that one leg will be shorter than the other. There isn't much you can do to change the length of the leg, other than undergo surgery. What you can do is avoid further injury.
Your foot, knee, hip and back all are affected by a change in leg length. This changes the way you walk, run and do other activities. You're more at risk for stress fractures because you favor one side over the other. Other overuse injuries, like tendonitis, are also possible.
Read More: How to Stretch Uneven Legs
Fixing Leg Length Problems
There aren't many options to fix a broken leg, especially in adults, because bones stop growing in length in adulthood. The most common fix is to put a small lift in the shoe of the leg that's shorter. This can make up for the size difference and put your foot, knee, hip and spine back into place. Another option is to surgically lengthen the leg by cutting the bone, pulling it apart slightly, and letting it heal.
Unfortunately, there aren't any exercises you can do to make your leg longer. You can, however, make your current workout accommodate your different leg lengths. Lower-body workouts are going to be the most affected by a leg length discrepancy. If your legs are uneven, the worst exercises to do are bilateral movements, like the squat and deadlift, that work both legs at once. Because your legs are a different length, these exercises distribute weight unevenly and cause your legs and back to move out of place.
Exercises that work one leg at a time, like lunges and single-leg squats, are much better because they allow each side to move freely. That means you won't be forcing yourself into any position that might hurt.
Read More: Hip Alignment & Leg Pain
Work your legs one at a time, so that it doesn't matter how tall each one is.
How-To: Hold a dumbbell in each hand. Stand tall and give yourself some room. Step forward far and drop your back knee down towars the ground. Step up with that foot so that your feet are even, then step forward with the other foot. Try to do 10 lunges on each leg.
Just because your legs are uneven doesn't mean you can't train them. This exercise gives you the leg muscle-strengthening benefits of regular squats without the pain.
How-To: Stand in front of a bench, chair or couch and face away from it. Hold dumbbells in your hands, anywhere from 5 to 10 pounds. Stand on one leg and lift the other leg up straight in front of you. Bend the leg you're standing on and reach your butt back to sit on the bench. Reach the dumbbells forward as you go down. Then, stand back up on the leg that's on the ground.
For a low-impact single-leg strength exercise, try the step-up.
How-To: Stand in front of a box, bench or chair that has a flat surface. It should be around knee-height. Plant one foot up on the box. Lean forward and push down with that leg, lifting yourself up until you're standing tall with both feet on the box or bench. Then, step back down with the same leg you stepped up with. Do an even number of reps on each side.