Hips – again!
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If you’ve been following this series over the past few years, you know that I have, on numerous occasions, discussed the ever-increasing evidence supporting the importance of maintaining good balance and strength of the hip muscles to prevent or treat a variety of running injuries involving the knees, legs, or feet.
First and foremost among these is the condition commonly known as Runner’s Knee (Articles #72 and 103), also known on occasion as patellofemoral pain syndrome (PFPS), anterior knee pain, and chondromalacia patella. Another common injury that is thought to be caused by faulty hip movement patterns is iliotibial band syndrome (Articles#11).
A causative factor in both conditions is thought to be an imbalance in strength of the internal/external rotators and abductor/adductor muscles of the hip. Re-establishing the proper proportionality of power and motor control is critical to resolving (and preventing) these conditions.
I’ve also spend a fair amount of time expounding on the lack of evidence implicating the impact forces generated by running in the development of knee (and hip) arthritis, contrary to popular myth. I’ve also explained the difference between the “traditional” form of arthritis – between the femur (thigh) and shin (tibia) – that is the type that may eventually lead to a joint replacement, and the category of Runner’s Knee that is between the patella (knee cap) and femur, that rarely requires a replacement.
The causes of knee arthritis (osteoarthritis) are still not clearly known. While many believe there likely are bio-mechanical factors at play, no one knows for sure what those might be.
A paper published in the Journal of Orthopedic and Sports Physical Therapy (Jul 2016) not too long ago attempted to answer that question. Investigators conducted a systematic review of previous studies that compared hip strength in those individuals with symptomatic knee arthritis to a control group without arthritis.
The researchers also conducted a meta-analysis of all the data from the previous studies, combining all the figures “under one roof” to, in effect, create a single study with a larger volume of information from which to draw conclusions.
Those conclusions were somewhat limited; there was a clear difference in hip abductor strength between the two groups (the arthritis group being weaker, as one might suspect), but no significant difference with respect to any other muscle groups, including the external rotators (which I would have suspected). The authors speculated, as others have in the past, that weakness of the abductors leads to a drop of the opposite side of the pelvis, which alters the alignment of the leg during the stance phase of gait, in turn leading to abnormal weight distribution through the knee joint.
The relevance of this finding may also be limited, however, since we don’t really know if those with arthritis developed this condition because they had this weakness, or did the weakness develop because of altered gait mechanics due to the pain of the arthritis. The authors do note that they found no studies in the literature that evaluated hip strength as a factor in the development of knee arthritis, so we can’t know the answer to that question for sure.
What may be of relevance is the possibility that targeting these muscles with strengthening and motor control exercises may be effective in mitigating some of the pain and dysfunction once the arthritis has already developed, since it would theoretically improve alignment and weight-distribution through the knee joint.
Whether such a program would in fact be beneficial is, at this point, speculative, but certainly an interesting question to be answered by a future research study. In the meantime, I consider these findings interesting enough to reinforce my belief that maintaining good balance of the muscles of the hip is a key component in addressing a wide variety of lower extremity running injuries and probably as important in terms of preventing such problems.