Another cause of ACL injuries are knee dislocations in the setting of high-energy traumatic injuries. In these cases, careful attention should be taken to assess other ligamentous and possible neurovascular injuries to the knee joint.
Classic history and presentation: Active, younger patients will more commonly rupture their ACL. A common presentation includes a patient who reports hearing / feeling a "pop" at the time of injury during an athletic activity. Additionally, hemarthrosis will commonly be seen within 2 hours of the suspected injury.
- Age – Mean age of incidence is 29 years (+/- 11 years), but this injury can occur across all ages. Peak incidence varies based on sex:
- Male peak incidence – 19-25 years old
- Female peak incidence – 14-18 years old
- Sex / gender – Both sexes can be affected, with a higher rate seen in the female population.
- Noncontact and contact sports activities (eg, football, lacrosse, soccer, basketball).
- Anatomical risk factors for youth include increased anterior pelvic tilt, increased femoral anteversion, narrow intercondylar notch, increased posterior tibial slope, and a small ACL.
- Female sex hormones (estradiol).
- A valgus knee (anatomic versus dynamic). In dynamic valgus, the combination of adduction of the hip and valgus moment on the knee upon landing results in increased strain on the ACL.
- Neuromuscular activation patterns (quad dominant).
- Lachman grade 1 – 3-5 mm anterior translation of the tibia in relation to the femur
- Lachman grade 2 – 5-10 mm anterior translation of the tibia in relation to the femur
- Lachman grade 3 – greater than 10 mm anterior translation of the tibia in relation to the femur
- Modifiers –
- A: firm endpoint
- B: no endpoint