An ACL injury is a common yet complex mechanical failure that causes the knee to give way during pivoting and landing. Explore the precise mechanism of ACL tears, from the instant of injury to clinical examination, surgical reconstruction and return to sport. ⏱ Chapters 0:00 Intro 0:40 Core Answer 1:16 Anatomy 1:58 Non-contact mechanism 2:40 Load versus capacity 3:17 History before hardware 4:00 Examination · Lachman 4:39 Functional instability · pivot shift 5:19 Radiograph 6:02 MRI 6:44 Acute management 7:21 Operate or rehabilitate 8:12 Graft selection 8:55 Graft failure · age 9:36 Surgical timing 10:23 Reconstruction geometry 11:06 Failed reconstruction 11:55 Lateral augmentation 12:40 Return to sport 13:24 Recap This comprehensive Orthovellum lecture covers everything you need to know about anterior cruciate ligament injuries. We break down the biomechanics of the non-contact pivot mechanism, the diagnostic power of the Lachman and pivot shift tests and the characteristic MRI findings like bone bruises and Segond fractures. Learn the critical principles of ACL reconstruction, including graft selection, anatomic tunnel placement and the criteria for a safe return to sport. 🦴 IN THIS VIDEO YOU'LL LEARN • The functional anatomy of the ACL and its role as the primary restraint to anterior tibial translation • The classic non-contact injury mechanism involving deceleration, valgus collapse and internal rotation • How to perform and interpret the Lachman, anterior drawer and pivot shift clinical tests • The differential diagnosis for an acute haemarthrotic knee, including patellar dislocation and meniscal tears • Identifying key radiographic and MRI findings such as the Segond fracture and kissing contusion pattern • The rationale for selecting different graft types like bone-patellar tendon-bone and hamstring autografts • Why anatomic femoral tunnel placement is critical to avoid graft failure and recurrent instability • The importance of delaying surgical reconstruction to regain range of motion and prevent arthrofibrosis • The criteria and typical timeline for a safe return to sport after ACL reconstruction 📌 KEY TAKEAWAYS ✔️ A tense haemarthrosis within hours of a twisting injury is an ACL rupture until proven otherwise. ✔️ The pivot shift test is the most specific clinical sign of functional rotatory instability. ✔️ A Segond fracture on a radiograph is pathognomonic for an ACL tear. ✔️ Bone-patellar tendon-bone autograft remains the gold standard for young, high-demand athletes. ✔️ Wait at least 3 weeks post-injury before reconstruction to restore motion and reduce arthrofibrosis risk. ✔️ Allografts have a significantly higher failure rate in patients under 25 years old. 👩⚕️ WHO THIS IS FOR This video is designed for orthopaedic trainees, medical students and sports medicine clinicians seeking a rigorous understanding of ACL injuries, as well as curious patients looking to understand their diagnosis and surgical management. 📚 RELATED TOPICS: Anterolateral Ligament Complex and Lateral Extra-articular Tenodesis · Meniscal Tears: Repair vs Meniscectomy · Posterior Cruciate Ligament Injuries · Multi-ligamentous Knee Dislocation and Vascular Assessment · Patellar Instability and MPFL Reconstruction · Principles of Sports Physiotherapy and Neuromuscular Training 🔗 More free orthopaedic teaching at Orthovellum.com — subscribe for weekly videos. 🎨 CREDITS • Van Dyck P et al., Journal of the Belgian Society of Radiology 2016 — CC-BY 4.0 — https://pmc.ncbi.nlm.nih.gov/articles/PMC6100662/ • Adwan H et al., Cureus 2025 — CC-BY 4.0 — https://pmc.ncbi.nlm.nih.gov/articles/PMC12007960/ • DBCLS, CC BY 4.0 — sagittal knee section, recoloured to episode palette — CC-BY 4.0 — https://bioicons.com/ ⚠️ DISCLAIMER: Educational only — not individual medical advice. Always consult a qualified clinician for diagnosis and treatment. #orthopaedics #orthovellum #aclinjury #kneeinjury #sportsmedicine #aclreconstruction #orthopedicsurgery #acltear #knee #sportsinjury #kneesurgery #arthroscopy #aclrecovery #medicaleducation