Once damaged, joint cartilage never completely regenerates. This is due to absence of vascularisation, slow cellular turnover and impossibility for inflammation mediators to reach the cartilage lesion. Even small lesions involve alteration in joint functionality and can cause invalidating pathologies. Treatment is complex and the surgical techniques used to repair the joint surfaces do not give satisfactory and durable results because the new tissue produced is fibrous cartilage. The aim of this study is to evaluate whether ovine embryonic stem cells transplanted in experimental lesions can differentiate into chondrocyte cells and if the new cartilage is of ialine type. For that purpose, we used the ovine species. The evaluation of reparative tissue was performed 1, 2 and 6 months after cell inoculation with histological, immunohistochemical and in situ hybridization methods. Bare lesions and Tissucol-implanted lesions were used as controls. Results confirm the stem origin of the reparative tissue with stem cells differentiating prevalently into chondrocytes and rarely into fibrocytes.