“The knee bone’s connected to the…hip bone” may be your therapist’s greatest clue to solving your knee pain. How many patients have gone to physical therapy for knee pain and received an ultrasound & VMO exercises only to be disappointed in his or her outcome? What exactly is the link between knee pain and hip weakness? What does the research tell us?
Patello-femoral pain syndrome (PFPS) is the most common condition seen in an orthopedic practice. It is the most prevalent injury in persons who are physically active. Iliotibial band syndrome (ITBS) is the second most common overuse injury in runners. Anterior cruciate ligament (ACL) injuries are one of the most common ligament injuries in people who engage in athletics. What common factor contributes to ALL of these orthopedic conditions? You guessed it!! Weak hips! Read on for the proof.
In a recent review of the literature, Reinman cited 51 articles that provide some degree of evidence correlating proximal factors to knee loading and knee injury. The position of the knee relative to the hip during weight bearing activities is a predictor of dysfunction. Excessive hip adduction and internal rotation can adversely affect the kinematics and kinetics of the entire lower extremity. This combined motion produces a “dynamic” knee valgus. A valgus moment places a tensile strain on the iliotibial band as well as the medial soft tissue restraints of the knee, particularly the ACL and medial collateral ligament. Claiborne et al and Hollman et al have reported that reduced hip strength is related to greater knee valgus angles. In the presence of hip abductor weakness, the opposite hip may drop during single-leg support causing a Trendelenberg sign. This is especially apparent during a slow, “controlled” descent down a step. A great functional test!
Why is it that the incidence of ACL injuries and PFPS is greater in women? Prins et al concluded that females with PFPS exhibit impaired strength of the hip extensors, abductors, and external rotators. Chen and Powers report that females with PFPS exhibit excessive “dynamic” Q-angles, especially with descending stairs. Pollard et al states that females demonstrate insufficient utilization of the hip extensors due to decreased knee and hip flexion during a jump squat for example. This leads to increased quad activation in the presence of a valgus knee and localizes the impact load onto the patella to a much smaller surface area.
So what if you’re a runner? Ferber et al looked at 283 studies that examined running-related injuries and concluded that the connections between weak hips and running were far more conclusive than the connection with flat feet (over-pronation). Interestingly, Earl et al prescribed a hip strengthening program to healthy female runners for 8 weeks and, in addition to improved hip strength, they measured a 57% decrease in pronation while running. Strengthen the hips and ditch the orthotics? Maybe.
If it hasn’t become obvious yet, hip weakness has been proven as a predictor of knee dysfunction. So in addition to your runs or to your crunches, you need a hefty dose of hip resistance training. Call us and we can get you started!!