Introduction: The results of treating chondral lesions with microfracture have been well documented. The lesion heals by fibrocartilage and the functional results tend to deteriorate through time.

Hypothesis: The use of steroids an platelet rich plasma (PRP) as coadjuvants to microfracture for the treatment of full thickness chondral lesions improve the results of this marrow stimulating technique.

Purpose: To macroscopically, histologically and molecularly evaluate the repair tissue generated after treating full thickness chondral lesions with microfracture and local steroids or PRP in an animal model.

Materials: Experimental in-vivo study in 40 femoral condyles (FC) from New Zealand rabbits. Chondral lesions were induced in all the samples and divided into 4 groups:

Group 1: control, lesion left untreated.

Animals were sacrificed after 3 months and the samples were evaluated macroscopically, histologically (H and E, Toluidine Blue) and molecularly (RT-PCR for Col1 and Col2). The results were analyzed with ANOVA and Bonferroni tests (p< 0.05).

Results: Macroscopy: the control group had no healing tissue. In all the other groups there was a variable presence of a fibrocartilaginous tissue without significant differences among groups.

Histology: all the groups had the presence of fibrocartilage.

Molecular analysis: all the groups had a significantly poorer Col2/Col1 relation when compared to normal hyaline cartilage, without significant difference among groups.

Conclusions: The local use of betamethasone and PRP as coadjuvants to microfracture does not improve the macroscopical, histological and molecular results of the treatment of full thickness chondral lesions.