Have you ever tried to be someone you're not? It's pretty hard work,
but in the beginning it can seem like it's working out well. You think you have
everybody fooled. It's a good feeling. Then, at some point down the line the disguise starts to crack, and all of a sudden other people aren't so fooled anymore.
This is similar to what happens to labrum in a dysplastic hip. For those of you who aren't anatomy geeks, the labrum is a ring of cartilage around the edge of the hip socket that helps to stabilise it. Part of the reason acetabular dysplasia can go unnoticed for so long is because the labrum steps up and says "This joint is unstable! Don't worry guys, I've got this covered." And he starts to become thicker in order to act like bone and take more of the load of the joint. He feels pleased with himself. He has everyone fooled. The truth is, the labrum can take up to 11% of the load in a dysplastic hip joint, whereas in a normal joint this would only be 1-2%.
In time though, he starts to realise that this isn't working out so well. His facade starts to break down. He can't take the load of a hip joint, what was he thinking?! This can't work in the long run. "I can't be bone," he says, "I am labrum. That is who I am."
'Acetabular rim syndrome' occurs when the labrum around the edge of the acetabulum starts to become injured or torn from the shallow socket and malaligned joint, and this is where the real situation begins to reveal itself. The labrum can often be where it all starts for many adults experiencing the first symptoms from a dysplastic hip. These symptoms include clicking, locking, catching and giving way of the hip joint. A recurring groin strain is often spoken of as the early symptoms, and sometimes 'C-sign' pain (pain deep in the joint). The labrum was faking it before, but now he's trying his best to protect the cartilage underneath. However, if the situation isn't dealt with, the articular cartilage will eventually be exposed and begin to become damaged itself.
This is what is believed to be the first step on the way to developing early osteo-arthritis of the hip.
Info taken from:
Burnett, R. S., Della Rocca, G. J., Prather, H., Curry, M., Maloney, W. J. & Clohisy, J. C. (2008), Clinical presentation of patients with tears of the acetabular labrum, The Journal of Bone & Joint Surgery 88 (7)
Gala, L., Clohisy, J. C. & Beaul´e, P. E. (2016) Hip Dysplasia in the Young Adult, Journal of Bone & Joint Surgery. 98-A (1)
Henak C.R., Ellis B.J., Harris M.D., Anderson
A.E., Peters C.L., Weiss J.A. (2011) Role
of the acetabular labrum in load support across the hip joint, Journal of
Biomechanics. 44 (12) doi: 10.1016/j.jbiomech.2011.06.011
McCarthy, J. C., Noble, P. C., Schuck, M. R., Wright, J. & Lee, J.
(2001) The Otto E. Aufranc Award: The
role of labral lesions to development of early degenerative hip disease, Clinical
Orthopaedics & Related Research. 393
Neumann, G., Mendicuti, A. D., Zou, K. H.,
Minas, T., Coblyn, J., Winalski, C. S., Lang, P. (2007), Prevalence of Labral tears and cartilage
loss in patients with mechanical symptoms of the hip: evaluation using MR
arthrography, Osteoarthritis & Cartilage. 15 (8)
