The capsular head of the proximal rectus femoris muscle: a review of the imaging anatomy of proximal muscle injury in professional athletes - early experience.

The detailed anatomy of the rectus femoris and corresponding injury appearances were first described in 1995. Since then, there has been little published to change our understanding of this complex anatomical area. More recent anatomical dissection work in 2004 and 2006 alluded to the presence of an altered configuration of the proximal tendon anatomy. Whilst widely accepted that the proximal rectus femoris muscle has two distinct tendon slips, the authors in 2006 described a third separate tendon slip arising from the anterior femoral capsule and this has been widely termed the 'capsular head'. We provide evidence that imaging features corroborate this revised anatomical concept. Whilst the clinical relevance of these findings is yet to be established, it remains important that our understanding of the radiological anatomy in this area advances with the forward growth of imaging clarity. In this review, we revisit anatomical concepts and present atypical injury cases that may be explained by the presence of a separate capsular head.