Despite the availability of various repair techniques, many meniscal tears remain irreparable. A freeze-dried chitosan-based formulation reconstituted in autologous platelet-rich plasma has shown potential in preclinical studies for enhancing suture-based meniscus repair. This study aimed at developing a fully arthroscopic ovine model of meniscus repair and evaluating chitosan/platelet-rich plasma's efficacy and safety as an augmentation strategy for suture-based meniscus repair. Unilateral radial lesions were induced in the medial menisci mid-body of 22 skeletally mature ewes. Tears were sutured inside-out. Two groups received a chitosan/platelet-rich plasma injection into the sutured lesions (0.5 or 1 mL doses, n = 6/group), while one group received a 1 mL autologous platelet-rich plasma injection (n = 5). The control group was only sutured (n = 5). A multiaxial mechanical tester and a hand-held probe were used respectively for mechanical (menisci and articular cartilages) and electromechanical testing (articular cartilages). All surfaces were then histologically assessed. Chitosan/platelet-rich plasma was resident in tears at 1 day and induced polymorphonuclear cell recruitment (assessed in n = 2 sheep). All operated joints developed signs of osteoarthritis compared to contralateral unoperated joints, with some of them displaying severe structural and functional changes. Instantaneous modulus properties and structural appearance of menisci and articular surfaces from chitosan/platelet-rich plasma treated groups were better than those of the other groups at 6 months postsurgery. Clinical pathology data were similar at baseline and at terminal in all groups, which suggests high safety. Chitosan/platelet-rich plasma implants helped limit cartilaginous degradation in joints with radially incised and sutured medial menisci and show promise as a treatment for meniscal tears.