Anterior cruciate ligament (ACL)-derived cells have a character different from medial collateral ligament (MCL)-derived cells. However, the critical difference between ACL and MCL is still unclear in their healing Potential and cellular response. The objective of this study was to investigate the mesenchymal differentiation property of each ligament-derived cell. Both ligament-derived cells differentiated into adipogenic, osteogenic, and chondrogenic lineages. In chondrogenesis, ACL-derived cells had the higher chondrogenic property than MCL-derived cells. The chondrogenic marker genes, Sox9 and alpha 1(II) collagen (Col2a1), were induced faster in ACL-derived pellets than in MCL-derived pellets. Sox9 expression preceded the increase of Col2a1 in both pellet-cultured cells. However, the expression level of Sox9 and a ligament/tendon transcription factor Scleraxis did not parallel the increase of Col2a1 expression along with chondrogenic induction. The present Study demonstrates that the balance between Sox9 and Scleraxis have an important role in the chondrogenic differentiation of ligament-derived cells. (C) 2009 Elsevier Inc. All rights reserved.