Running is a dynamic, repetitive movement pattern. The trouble with these types of activities is if you lack a good, basic movement and you perform a version that is slightly off over and over again, things don't work as well. It's kind of like a door that is on a hinge slightly crooked. You don't notice that the hinge is rubbing wrong at first, and the door opens fine the first 50, 100 times. After a while, the door doesn't swing as well and eventually, the hinge wears down and the door, while it might still open, doesn't function well. Your body functions much the same way. You can get away with certain faulty movement patterns for a while, but after enough times, something's gotta give. In the case of running, the poor knee (which should move forward and back, not side to side) is stuck between two joints that are supposed to be quite mobile (the ankle and the hip). The movements we perform in our every day lives do not favor ankle and hip mobility; as a result, the knee often loses some of its stability. Running with hips and ankles that lack mobility is setting that knee up to function like the crooked door hinge.
Hip extension is critical to good running mechanics. Our society is extremely forward in nature. We sit, hips flexed, at desks with our heads jutting forward. This shortens everything in the front of the body and reduces our ability to properly use the muscles in the back of the body. Schache, Blanch, and Murphy (2000) found a correlation between limited hip extension flexibility and increased anterior tilt during running. While there is little in the literature that discusses the importance of hip mobility as it relates to running stride, Saunders, Pyne, Telford, and Hawley (2004) point out a strong correlation between running economy and distance running performance; further, muscular stiffness and efficient mechanics are thought to decrease the amount of energy wasted on braking forces and vertical oscillation. If you do not have good hip mobility, you are going to be unable to extend your hip, leading to a more forward dominant running stride. This often leads to a running pattern that involves more hip flexion, causing the foot and knee to land more forward. As a result, the ground and the foot collide each time the foot lands, resulting in more braking forces. Couple this with poor ankle mobility, and there are more than likely going to be problems. One way to work on hip extension is to implement a corrective exercise program that emphasizes hip extension and mobility. Exercises such as squats, lunges, and bridging are great ways to begin to activate the hip area. More advanced and complex moves such as McGill's airplane, the Cook hip lift, and Bulgarian split squats can reinforce proper hip mechanics and gluteal activation if performed properly. It is also important to not neglect the ankle area. Implementing simple drills, such as seated ankle dorsiflexion, ankle circles, and inverserion/eversion, can dramatically increase ankle mobility. Remember, when implementing a strength and conditioning program, understand your goals and know what movement patterns and mechanics are necessary for success in your chosen sport. This, coupled with your current static and dynamic posture, should dictate the exercises you choose, not necessarily the exercises "everyone else is doing." Move well and move often.
Yours in health and wellness,
Schache, A.G., Blanch, P.D., & Murphy, A.T., (2000). Relation of anterior pelvic tilt during running to clinical and kinematic measures of hip extension. British Journal of Sports Medicine, 34(4), pp. 279-283.
Saunders, P.U., Pyne, D.B., Telford, R.D., & Hawley, J.A. (2004). Factors affecting running economy in trained distance runners. Sports Medicine, 34(7), pp. 465-485.