More than just a bump: Cam-type femoroacetabular impingement and the evolution of the femoral neck


Recent orthopaedic literature has implicated femoroacetabular impingement, the pathologic abutment of structural aberrancies in the proximal femur and acetabular rim, as an important cause of groin pain in young individuals and a potential factor in early idiopathic osteoarthritis. The etiology and risk factors for developing cam-type morphology are still unknown. The osseous anatomy of the proximal femur in humans is the culmination of nearly 400 million years of evolution. Coxa recta and coxa rotunda are the two predominant morphologies in modern animals. While the latter, characterized by a straight head-neck junction, is often present in cursorial creatures, the former, distinguished by high offset at this junction, is exemplified in most humans. Based on the ontology and phylogeny of the proximal femur, coxa rotunda probably developed from a more primitive coxa recta. We believe that cam-type morphology is neither a redevelopment of coxa recta nor a malformation such as slipped capital epiphysis. The aspherical osteocartilaginous bump is associated with an extended physis and has been noted to appear during mid-adolescence. While this protuberance may contribute to future pathology, the authors feel that increased loading of the hip, not impingement activities, during late childhood and early adolescence predispose patients to develop this morphology.

Hip Int 2011; 21(1): 1 - 8

Article Type: REVIEW



Vincent Y. Ng, Thomas J. Ellis

Article History

This article is available as full text PDF.

  • If you are a Subscriber, please log in now.

  • Article price: Eur 36,00
  • You will be granted access to the article for 72 hours and you will be able to download any format (PDF or ePUB). The article will be available in your login area under "My PayPerView". You will need to register a new account (unless you already own an account with this journal), and you will be guided through our online shop. Online purchases are paid by Credit Card through PayPal.
  • If you are not a Subscriber you may:
  • Subscribe to this journal
  • Unlimited access to all our archives, 24 hour a day, every day of the week.


  • Ng, Vincent Y. [PubMed] [Google Scholar]
    The Ohio State University Medical Center, Department of Orthopaedics, Ohio - USA
  • Ellis, Thomas J. [PubMed] [Google Scholar]
    The Ohio State University Medical Center, Department of Orthopaedics, Ohio - USA

Article usage statistics

The blue line displays unique views in the time frame indicated.
The yellow line displays unique downloads.
Views and downloads are counted only once per session.

No supplementary material is available for this article.