Long-lasting repair of articular cartilage lesions remains a clinical unmet need, despite the multiple distinct approaches clinically implemented in the last decades. Under this thesis, a thorough literature review and analysis was performed in order to understand what the current clinical and scientific practices are, and what are their main reported benefits and limitations, towards identifying new ways to tackle the current limited repair of cartilage lesions. The field of tissue engineering and regenerative medicine has delivered extraordinary findings in subjects such as cell biology, material science, biochemical and biomechanical cues and animal models, allowing the development of innovative and sophisticated solutions, particularly for cartilage repair. When aiming the regeneration of a functional articular cartilage tissue, the presence of healthy chondrogenic cells, at a therapeutically relevant amount, exactly at lesion site, is considered paramount. Several advanced scaffolding systems and surgical approaches have been developed to deliver cells and sustain tissue growth, yet retention of cells in situ has been suboptimal. Herein, the experimental work developed in this thesis explores the potential of a methacrylated gellan gum (GGMA) hydrogel to deliver and retain chondrogenic cells in lesion site, while providing 3D filling of lesion volume during development of the new chondral tissue. In vitro studies showed that GGMA hydrogel at 2% w/V is a suitable scaffold for encapsulation of human chondrogenic cells, such as human chondrocytes or human adipose derived stromal/ stem cells. Cells were maintained viable up to 21 days at densities ranging from 5-10 M/mL and chondrogenic differentiation was demonstrated by high collagen type II over-expression concomitant with low collagen type I. Techniques such as RT-qPCR and immunohistochemistry (IHC) were used to assess chondrogenesis. Such promising in vitro outcomes supported the in vivo performance testing in a rabbit model with an induced critical-size cartilage defect. Herein, autologous adipose derived stromal/stem cells (10 M/mL) were delivered within GGMA 2 % w/V hydrogel by injection into lesion site and allowed for regeneration for 8 weeks. Histological analysis of tissue explants demonstrated new tissue composed by hyaline-like cartilage (stained by safranin O) and collagen type II (identified by IHC). These histological results classified by O’Driscoll scoring were superior than those obtained for lesions treated by the gold-standard microfracture procedure (p<0.05) as well as for the untreated lesions (p<0.001). The gelification characteristics of the GGMA was compatible with an injectable system, which allows its application through the currently well-stablished minimally invasive arthroscopic procedures. Given this, a new surgical tool was developed to allow the hydrogel delivery inside the joint under a standard arthroscopic approach. The device was effective to deliver the methacrylated gellan gum hydrogel directly into the chondral lesion created in a cadaveric joint. The hydrogel was maintained isolated of the liquid arthroscopic environment during gelification time (approximately 5 minutes), avoiding dilution/ dispersion of the hydrogel within the articular cavity. Hydrogel was maintained in lesion site after removal of the device form the joint. The flexible design of the surgical tool allows adoption of additional features and application in distinct settings if further explored. The positive outcomes obtained under this thesis open an exciting route towards more efficacious and less invasive treatment procedure for cartilage repair, which is expected to increase cost effectiveness as compared to current treatment standards.