Structural and Functional Principles in Quadriceps Reconstruction.

Quadriceps muscle and tendon injuries are a significant cause of impairment of the knee extensor mechanism, ranging from minor muscle strains to complete tendon ruptures and extensive defects following oncologic resections. This narrative review provides a comprehensive analysis of contemporary concepts in anatomy, biomechanics, diagnosis, surgical management, and rehabilitation, with a particular focus on reconstructive techniques and functional outcomes. While most muscle injuries respond well to conservative management, complete quadriceps tendon ruptures typically require surgical repair to restore extensor continuity. Both transosseous suture techniques and suture anchor fixation demonstrate reliable outcomes, with no clear superiority in clinical results. Chronic ruptures present additional challenges due to tendon retraction and poor tissue quality, often necessitating advanced reconstruction methods such as V-Y tendon lengthening and augmentation with autografts, allografts, or synthetic materials. In cases of large defects, especially following soft-tissue sarcoma resection, free functional muscle transfer (FFMT) has emerged as a key reconstructive strategy. Common donor muscles include the latissimus dorsi, gracilis, rectus abdominis, and vastus lateralis, each offering specific biomechanical advantages. Functional recovery is strongly influenced by the extent of quadriceps preservation, with better outcomes observed when at least two muscle heads remain functional. Rehabilitation protocols vary depending on the surgical approach. Early controlled mobilisation is generally recommended after tendon repair, whereas FFMT requires a more cautious and prolonged rehabilitation process to allow for flap integration and reinnervation. Overall, optimal outcomes depend on a multidisciplinary approach combining appropriate surgical technique, individualized rehabilitation, and careful patient selection.