The Elusive Iliocapsularis
As with many things, one thing often leads to another. I had a patient with anterior hip pain and what i believed was iliopsoas dysfunction, but I wanted to know EXACTLY which muscles attached to the hip capsule, to make sure I wasn’t missing anything.
I turned up some great info, including a nice .pdf lecture, which I am including the link to along with a second paper that began my journey.
I had thought the iliopsoas attached to the hip capsule, but it turns out it doesn’t, but the iliocapsularis does along with a host of others, including one of my favs, the gluteus minimus, which was believed to be part of the psoas, but actually is a completely separate muscle. Did I mention that these are FREE, FULL TEXT articles?
Anyway, I began reading, with great interest, about the iliocapsularis and I found yet another great review paper on it, along with mechanical hip pain. This last paper has some real clinical pearls and I recommend reading it the next opportunity you have a bit of time.
I began thinking about when the iliopsoas fires in the gait cycle (terminal stance to mid swing). So, it is firing eccentrically at pre swing (perhaps limiting or attenuating hip extension?), then concentrically through early and mid swing, when it becomes electrically silent. During running gait, the activation pattern is similar. This muscle is also implicated in femoroacetabular impingement (FAI), or more correctly anterior inferior iliac spine subspine impingement (AIIS Impingement) or iliopsoas impingement (IPI). They all can cause anterior hip pain and they should all be considered in your differential.
The iliocapsularis muscle has its proximal attachment at the anterior-inferior iliac spine and the anterior hip capsule and does not attach to the labrum . Its distal insertion is just distal to the lesser trochanter. It can sometimes inset into the iliofemoral ligament and/or the trochanteric line of the femur. It is innervated by a branch of the femoral nerve (L2-4). It is believed to act to raise the capsule of the hip and be an accessory stabilizer of the hip.
OK, there you have it. the iliocapsularis. Another muscle you didn’t know you could access. It pays to know your anatomy!
https://www.mcjconsulting.com/meetings/2012/asm/ePosters/files/ISHA_Poster_202.pdf
