Purpose: Despite the large number of papers about regeneration of articular cartilage, the good results achieved in small animals are not replicated in large animal models and in humans. One possible reason is the frequent use of the osteochondral model, with perforation of the subchondral bone plate. As the most frequent pattern of lesion in humans is the Partial Thickness, new therapies should be tested in this model. However, while osteochondral model histological scoring systems are abundant, there is not a tool to evaluate the results of Partial Thickness model. Objective: to develop a new histological scoring system to be used in the Partial Thickness model of cartilage repair. Methods: histological sections of 30 ovine knees were reviewed to develop the new scoring system. They were stained with H&E, Safranin O, and Masson trichrome. Results: this paper describes in detail the new scoring system. It was divided in three main sections: repair tissue inside the lesion, cartilage around the lesion and degenerative changes in the base of the lesion. The score ranges from 0 to 21. The greater the score, the best the result of the cartilage repair. Conclusion: This new histological scoring system is the first one specific to Partial Thickness articular cartilage lesion model. Future studies will determine its correlation coefficient.