Fig. 1.

Histology of the superficial region of the normal and femoroacetabular impingement (FAI) labrums. a) In the normal labrum, the superficial region includes a single layer of cells on the surface and an adjacent area (marked by arrows), where cells line in parallel with the surface. b) In the FAI labrum cells are lost from the surface layer, and the cells in the superficial region are distributed in a more random fashion. The entire superficial region in the FAI labrum is expanded (marked by arrows). There are mostly thick collagen fibres in the surface layer of the normal labrum. The collagen fibres in the adjacent area are composed of both thick and thin fibres. c) Collagen fibres in the superficial region of the normal labrum are oriented in parallel with the labrum surface. d) Collagen fibres in the superficial region of the FAI labrum are disoriented and more heterogenous in the makeup of collagen fibres. Haematoxylin and eosin (H&E) staining was used in a) and b); Picrosirius Red staining was used in c) and d). Bars represent 50 µm (original magnification 200×).