Previously in this series, we discussed the importance of the hip labrum (here) and the capsuloligamentous complex (here) in hip stability. The 3rdand final part of this series will discuss the outer layer of stability of the hip, and the only contractile layer, the hip muscles, more specifically the hip cuff.
Hip Cuff Anatomy
There are over 20 muscles that cross and act on the hip joint. Fortunately, we will not be covering all of those muscles today. Although all muscles act to stabilize the hip, the hip cuff muscles play more of a stabilizing role, while the others play more of a hip movement role.
The hip cuff muscles consists of the gluteus medius and minimus of the gluteal region, the deep gluteal muscles consisting of the piriformis, superior and inferior gemellus, obturator externus and internus, and the quadratus femoris as well as the pectineus of the adductor region (Lindsay et al., 2017). Although all of these muscles have separate individual function to move the hip, they all work in sync to stabilize.
Stabilizing Function of the Hip Cuff
The glutes (med and min) act to stabilize the femoral head by drawing it into the acetabulum, creating a compressive force. This compression creates an increase in hydrostatic pressure which helps stiffen and stabilize the joint during weight-bearing parts in the gait cycle. This compressive force is possible due to the orientation of the glute med/min fibers being parallel with the head of the femur (Gottschalk, 1989).
The only muscle on the anterior portion of the hip that aligns parallel to the head of the femur and the orientation of the glutes is the pectineus. During normal walking, EMG acitivity is very similar to that of the glutes (Gottschalk, 1989).
The deep glutei muscles likely assist with minor adjustments to the hip and help provide extra stiffness to the joint (Gottschalk et al., 1989).
To summarize, the smaller glute muscles from the posterolateral aspect of the hip and the pectineus from the anteromedial aspect of the hip work together to produce a force along the same line of pull on the femur, one anterior the other posterior, to create compression of the femoral head in the acetabulum. This leads to an increase in hip stability.
In the case of hockey players, where the majority (~70%) have labrum tears (covered in this article) and possibly stretched iliofemoral ligaments (covered in this article), neuromuscular control of the hip joint is not only important for hip health, but also for performance. Having good hip control at the arthrokinematic level will keep the femur centered in the acetabulum and allow the larger muscles around the hip to function optimally during the skating stride. In terms of hip health, if the femur is sitting anteriorly on the joint, it can impinge on structures of the anterior hip (capsule, labrum, psoas tendon) when it flexes and cause pain. This can lead to fraying of labrum, tendinopathies, and irritation of the iliofemoral ligament. It will also put more strain on structures such as the labrum and ilifemoral ligament simply in an upright position.
I think the most important thing to takeaway from this is that we can train the hip cuff to stabilize when the static structures can’t. There are many different ways to do this, and no one right way, while ensuring good glute strength and control, with open and closed chain exercises.
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References
Lindsay, D., Cuskelly, G. (2017) Preserving the Active Hip: New Advances in Hip Rehabilitation (October 2017).
Gottschalk, F., Kourosh, S. O., & Leveau, B. (1989). The functional anatomy of tensor fasciae latae and gluteus medius and minimus. Journal of anatomy, 166, 179.