Condylar Sag After Orthognathic Surgery: Biomechanical Mechanisms, Surgical Factors, and Clinical Prevention

Condylar sag is a clinically important consideration following orthognathic surgery, with potential consequences for occlusal stability, skeletal relapse, and long-term temporomandibular joint (TMJ) health. Despite advances in digital surgical planning, fixation techniques, and imaging modalities, postoperative alterations in condylar position remain inconsistently defined, variably interpreted, and often managed without a unified conceptual framework. This narrative review synthesises contemporary literature (2000-2025) to address this gap by examining condylar sag from a biomechanical and functional perspective. The review focuses on the interaction between proximal segment biomechanics, neuromuscular adaptation, magnitude and direction of surgical movement, fixation strategy, and the adaptive capacity of the TMJ. The synthesised evidence indicates that condylar sag should not be viewed as a uniform technical complication but rather as a dynamic and frequently modifiable response influenced by perioperative decision-making and postoperative functional loading. Diagnostic challenges related to imaging modality and timing are highlighted, emphasising the importance of correlating radiographic findings with clinical symptoms and functional assessment to distinguish physiological adaptation from pathological instability. Preventive and management strategies are discussed across the preoperative, intraoperative, and postoperative phases, underscoring the roles of accurate condylar seating, controlled biomechanics, and structured rehabilitation. By shifting emphasis from incidence-based descriptions toward a mechanism-oriented understanding, this review provides a clinically relevant framework to minimise significant condylar sag, preserve TMJ health, and optimise long-term stability following orthognathic surgery.