The takeaway is that if the hip abductors (the muscles that move the lower leg sideways away from the body) and the hip flexors (muscles that move the lower leg in toward the body) are weak, the knee doesn't track as well as it should.
If the knee rolls inward while running, there is an increase in the risk of patellofemoral pain syndrome, iliotibial band syndrome and other running overuse injuries.
Bottom line: Weak hips may be one of the causes of knee pain and lower leg injuries.
The side plank exercise is one simple and effective to increase hip strength and stability. Here's how to do it correctly.
The Side Plank Exercise
- Begin by laying on your side on the floor.
- Position your elbow on the floor just under your shoulder.
- Lift up on that elbow and keep your body stiff from head to toe.
- Hold this position for a count of 10 and lower your hip to the floor.
- Rest and repeat three times.
- Switch sides and repeat the exercise on the other hip.
- You can increase the effect of this exercise by lifting the top leg up toward the ceiling. Repeat the leg lift 10 times slowly and return to the start position.
- If you prefer, you can do these exercises on a hand rather than an elbow.
Also See: The Plank Exercise for Hip and Core Strength
Source:
R. Ferber, et al. Suspected Mechanisms in the Cause of Overuse Running Injuries: A Clinical Review. Sports Health, May 2009.

