It has been reported that the knee is the most common location for an injury. This may be due to the fact that the knee eccentrically absorbs more than 40% of the energy associated with ground contact. Running has been shown to increase the external force on the knee 5x the force of that generated while walking!
What is even more important to understand is the effect that the trunk and pelvis position in relation to your center of mass can impact the direction of force directed at the knee. “For example, excessive movement of the COM over the stance limb during an activity such as landing from a jump on one foot could move the resultant ground reaction force vector lateral to the knee joint center, thereby creating a valgus moment at the knee.” An example of this includes leaning your trunk over the leg in contact with the ground in an attempt to keep your balance.
Hip adduction promotes dynamic knee valgus, “which would be expected to strain the soft tissue restraints that limit knee valgus such as MCL and ACL. Without even taking trunk and pelvis position into account, “the peak valgus moment is two and a half times greater during running that it is during walking.”
Theoretically, repetitive stress to structures in poor kinematic positions may increase the risk of sports-related injury. It is important to train the body to move in an optimal strategy and limit poor movement patterns such as excessive dynamic knee valgus. Practicing landing and working on these faulty mechanics is a great drill to add to your running training program. It has been shown that using the hip extensors to absorb external forces from the ground can reduce the knee valgus moment in women post-op ACL reconstruction. Hip strength or motor control? The debate continues, but likely it is a combination of both that should be considered in a runner’s training program. Be sure to have the sound on to learn MORE!
Novacheck TF. The biomechanics of running. Gait Posture. 1998;7(1):77–95.
Van Gent RN, Siem D, van Middelkoop M, van Os AG, Bierma-Zeinstra SMA, Koes BW. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. Br J Sports Med. 2007;41(8):469–80; discussion 480.
Powers CM. The Influence of Abnormal Hip Mechanics on Knee Injury: A Biomechanical Perspective. J Orthop Sport Phys Ther. 2010;40(2):42–51.
Tsai L-C, Powers CM. Increased Hip and Knee Flexion During Landing Decreases Tibiofemoral Compressive Forces in Women Who Have Undergone Anterior Cruciate Ligament Reconstruction. Am J Sports Med. 2013;41(2):423–429.