After 20 years of studying the mechanics of knee injury and publishing over 100 scientific papers on this topic, I have come to one simple conclusion: most knee injuries stem from poor hip strength and/or control. While this may sound like a fairly strong statement, in reality, it makes a lot of sense. Consider the following line of reasoning:

1)    The knee joint is the articulation (connection) of the femur (thigh bone) and tibia (shin bone).

2)    As such, the femur comprises half the knee joint.

3)    Femur motion is controlled by the hip musculature; particularly the gluteus maximus and gluteus medius.

4)    Therefore, the hip muscles control half of the knee joint!

In a recent publication, I discuss the influence of altered hip mechanics on 3 of the most common knee conditions seen in orthopaedic practice: patellofemoral pain, iliotibial band syndrome and anterior cruciate ligament injury. In this paper, I review the growing body of scientific literature suggesting that strength and motion impairments at the hip, pelvis and trunk may contribute to knee injuries. Interestingly, research suggests that females are more likely to exhibit these tendencies than males.

Based on the recent evidence being published in clinical, biomechanics, and sport medicine journals, interventions that address impairments proximal to the knee may be beneficial for patients who present with various knee conditions. More specifically, a biomechanical argument can be made for the incorporation of pelvis and trunk stability as well as dynamic hip joint control into the design of knee rehabilitation programs. While I am not discounting the importance of quadriceps and hamstring strength with respect to knee mechanics, I argue that there should be EQUAL emphasis on both hip and knee strength. Unfortunately most rehabilitation protocols (particularly for patellofemoral pain and ACL reconstruction) do not place enough importance on high level hip muscle strengthening and neuromuscular retraining.

In support of this premise, recent research out of Brazil suggests that hip strengthening may be more important than quadriceps strengthening for the treatment of patellofemoral pain.^1-3 Furthermore, a randomized controlled trial published from our group demonstrated that isolated muscle hip strengthening improved pain and functional outcomes in females with chronic patellofemoral joint symptoms.

Obviously, more research needs to be conducted to fully validate the role of altered hip strength and mechanics on knee injury. However the research that is emerging is leading to a paradigm shift in our thinking of knee injury mechanics, rehabilitation and injury prevention strategies. Keep in mind that while the pain may be at the knee, the cause of the symptoms may be coming from somewhere else. Obviously, a thorough biomechanical analysis would be necessary to make this determination.
 
References

1. Fukada TY, Rossetto FM, Magalhaes E, Bryk FF, Lucareli PR, de Almeida Aparecida Carvalho N. Short term effects of hip abductor and lateral rotator strengthening in females with patellofemoral pain syndrome: A randomized controlled clinical trial. J Orthop Sports Phys Ther. 2010;40:736-742.

 

2. Fukada TY, Melo WP, Zaffalon BM, Marconded FR, Magalhaes E, Bryk FF, Martin RL. Hip Posterolateral musculature strengthening in sedentary women with patellofemoral pain syndrome: A randomized controlled clinical trial with 1-year follow-up. J Orthop Sports Phys Ther. 2012;42:823-830.

 

3. Nakagawa TH, Muniz TB, Baldon RM, Maciel D, de Menezes Reiff RB, Serrao FV, Clin Rehab. The effect of additional strengthening of hip abductor and lateral rotator muscles in patellofemoral pain syndrome: A randomized controlled pilot study. 2009;22:1051-1060.

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