Hydrogels for Osteochondral Interface Regeneration: Biomaterial Types, Processes, and Animal Models.

The osteochondral interface (OCI) is a structurally and functionally complex tissue whose degeneration or injury often results in poor healing and joint dysfunction due to its avascular and hypocellular nature. Conventional surgical treatments remain suboptimal, prompting growing interest in regenerative approaches, particularly with the utilization of hydrogel-based biomaterials that can mimic the extracellular matrix and support osteochondral regeneration. This study reviewed types of hydrogels, scaffold processing techniques, and animal models for OCI regeneration. Our search demonstrated that gelatin, alginate, chitosan, and hyaluronic acid were the most frequently investigated hydrogels. Layered constructs dominated current scaffold designs, while advanced methods such as 3D printing and extrusion demonstrated unique potential to create graded architectures resembling the native OCI. Rabbits were the most widely used in vivo models, though translation will require larger animal studies with clinically relevant defect sizes. Future efforts should focus on developing mechanically reinforced, biologically active, and continuously graded hydrogels, supported by standardized preclinical validation in large-animal models, to accelerate translation toward clinical solutions for osteochondral regeneration.