Musculoskeletal injuries often involve irregular geometries, heterogeneous tissue interfaces, and mechanical demands that challenge conventional grafts and prefabricated tissue-engineered constructs. In situ bioprinting seeks to address these constraints by coupling patient-specific imaging and path planning with direct deposition of cells, biomaterials, and bioactive cues within living defects. This review links intraoperative constraints to technology and bioink selection across musculoskeletal injuries, separating direct in vivo printing from enabling studies and distinguishing geometric feasibility, tissue formation, and functional recovery. Extrusion-, inkjet-, light-, laser-, and assembly-based strategies are compared in terms of printability, cellular exposure, spatial control, and compatibility with the operative environment. We further examine collagen, gelatin methacryloyl (GelMA), alginate, hyaluronic acid derivatives, decellularized extracellular matrix, fibrin, cellulose-based materials, self-assembling peptides, mineral phases, and synthetic networks according to their biological and mechanical roles. Direct in vivo studies demonstrate the feasibility of conformal deposition and tissue formation in bone, cartilage, and temporalis muscle defects. Studies of vascularized constructs and tendon-bone interfaces provide additional evidence, largely from fabrication followed by implantation. However, small cohorts, short follow-up, and accessible or relatively low-load models predominate; durable mechanical and functional superiority over standard treatment remains unproven. Translation will require reliable intraoperative imaging and registration, wet-tissue fixation, vascular perfusion, sterile material exchange, closed-loop process control, scalable manufacturing, and clinically relevant large-animal comparisons. In situ bioprinting should therefore be developed as an integrated surgical platform that complements established reconstruction through digital planning, regenerative materials, and precise delivery. Standardized reporting and long-term functional endpoints are essential to establish clinical value.