Tendinosis lesions show an increase of glycosaminoglycan amount, calcifications, and lipid accumulation. Therefore, altered cellular differentiation might play a role in the etiology of tendinosis. This study investigates whether adolescent human tendon tissue contains a population of cells with intrinsic differentiation potential. The results suggest that this population of explanted human tendon cells have an intrinsic differentiation potential. This support the hypothesis that there might be a role for altered tendon-cell differentiation in the pathophysiology of tendinosis. BMC Musculoskeletal Disorders, 2007, 8:16