Match the following classic mechanisms of knee injury with their most characteristic diagnostic physical examination finding.
- Noncontact deceleration and pivoting injury followed by rapid-onset hemarthrosisIncreased anterior tibial translation at 20 to 30 degrees of knee flexion
- Direct blow to the anterior proximal tibia in a flexed knee (e.g., dashboard injury)Posterior displacement of the tibial plateau when the hip and knee are flexed to 90 degrees
- Twisting injury on a weight-bearing, flexed knee followed by delayed-onset effusion and mechanical catchingPain or a palpable click during tibial rotation with varus or valgus stress applied during knee extension
- Sudden, eccentric quadriceps contraction resulting in a palpable infrapatellar gap and high-riding patellaInability to actively extend the knee or maintain a straight leg raise against gravity
Answer
ACL tears match with increased anterior tibial translation; PCL tears match with posterior tibial displacement; meniscal tears match with a painful click on rotation; and patellar tendon ruptures match with the inability to actively extend the knee.
Each mechanism of injury strongly points to a specific anatomical disruption in the knee, which is subsequently confirmed by its corresponding targeted physical examination finding based on knee biomechanics.
Step-by-Step Solution
Key Concept
Biomechanics, physical examination, and diagnosis of acute knee injuries