Monday, January 5, 2015
Does Movement Impact Hip Pain
Over the course of the last year, we have made several inferences about the impact that movement has on tissue stress and bony alignment at the hip and suggested the impact this may have on pathology in the athletic hip. All to often in the medical sciences, we seek a peer reviewed research paper to guide our critical thinking and clinical thought process. However, should we or could we use some of the basics we were taught in anatomy and biomechanics to guide us? If we can, could this guide some of our thought process in relation to hip pathology and movement assessment.
If we simply look at bony anatomy of the hip alone (pictured here), we have the head of the femur and the acetabulum of the pelvis. In an ideal situation, the femur is centered at the intersection of the X in this picture. With the femur positioned here, we can see that a movement of pure adduction of the hip will bring the intertrochanteric line in closer proximation to the anterior labrum. If adduction is combined with internal rotation, then you bring the greater trochanter in closer proximation to the anterior superior labrum. If you combine these two motions with hip flexion, then this places these structures in even closer proximation to the labrum.
It is the combination of these motions that can result in femoral acetabular impingement (FAI) or hip pain in the athlete. It is becoming fairly well accepted that the combination of these motions is one of the driving factors that leads to FAI, cam impingement, labral tears and anterior hip pain in athletes. There is an increased number of papers as well as orthopedic textbooks that describe these motions and the association with this type of pathology. Due to the higher loads associated with athletics, it is also one reason that we tend to see this more commonly in the athletic individual. Despite the fact that these motions are being more widely accepted as a cause and risk factor for developing FAI, rarely do we assess this during movement for these types of pathologies. Typically, this is assessed during supine examination and MRI. However, this begs the question, can we assess this with movement? Can we objectively quantify this during human movement in a meaningful way for both preventative techniques and rehabilitation? More importantly, does supine testing represent the true relationship between the acetabulum and femur in weight bearing positions?
To answer that question, lets look at a recent study published by Pullen et al in the American Journal of Sports Medicine in 2014. In this study, the authors wanted to look at the variability in acetabular coverage between supine and weightbearing.
Methods: 50 subjects 18 years or older who were referred for symptomatic hips were evaluated for femoral acetabular impingement. Each of the subjects were evaluated using standardized supine and weightbearing anterioposterior pelvic radiographs. Measurements were obtained in each position for acetabular coverage by two blinded reviewers for each of the 50 hips and compared.
Results: Statistically significant differences between supine and weightbearing radiographs were observed for all measurements of acetabular coverage. Measurements of acetabular coverage decreased between supine and weightbearing along with a considerable increase in pelvic tilt noted with weightbearing position in 45% of the subjects.
Discussion: Based on the above results, we see that acetabular coverage is decreased when moving from supine to weightbearing positions. A decrease in acetabular coverage equates to increased risk for FAI. In 45% of the subjects, there was also a notable increase in pelvic tilt associated with change in position from supine to weightbearing. Knowing that core strength and endurance is vital to stability of the pelvis, this would indicate an increase demand on the core for stability of the pelvis in weightbearing positions. It also points out the importance the core plays in preventing excessive pelvic tilt and hence altered acetabular coverage.
So, in going back to the previous question, does supine testing represent the true relationship between the acetabulum and femur in weight bearing positions or during sport, we know, based on this study that answer would be no. So, if acetabular coverage is not the same, then there is an alteration of not only bony alignment but also length tension relationships of the entire lumbopelvic complex. That said, should we look at the previously mentioned movements (adduction, internal rotation and flexion) that occur in the lower kinetic chain during weightbearing motions so we may identify those at increased risk for FAI?
Stay tuned next week and we will look at that further. We hope that you found this blog insightful and useful. As we stated previously, stay tuned and if you like what you see, SHARE THE PASSION! It is the biggest compliment you can give. Follow us on Twitter @ACL_prevention and tweet about it. #DMAOnTheMove and help us spread the passion and #movementonmovement.
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