From the Guidelines
Diagnosing an ACL injury requires an MRI as the gold standard imaging modality, as it can directly visualize the torn ligament and identify associated injuries, such as meniscal tears or bone bruises, with high sensitivity and specificity, as reported by Van Dyck et al 1. When suspecting an ACL injury, a combination of physical examination and imaging studies is necessary. A healthcare provider will typically perform specific tests, including the Lachman test, anterior drawer test, and pivot shift test, to assess ligament stability. These tests evaluate abnormal forward movement of the tibia relative to the femur, indicating ACL damage. Common symptoms include a popping sound at the time of injury, rapid swelling within 24 hours, pain, instability, and difficulty bearing weight.
Key Points to Consider
- MRI has many distinct advantages for the evaluation of the injured knee in the setting of negative radiographs, allowing earlier surgical intervention by obtaining a more accurate diagnosis 1.
- A retrospective study by Cecava et al, as mentioned in the evidence 1, showed that knee radiography is a highly specific screening test for internal derangement in patients <40 years old with acute knee injury, but knee effusion >10 mm on lateral radiograph should prompt consideration for the knee MRI examination.
- The presence of a bone contusion on MRI after acute knee trauma is highly predictive of the development of focal osteoarthritis 1 year after trauma, as reported by Koster et al, as mentioned in the evidence 1.
Importance of Early Diagnosis
Early diagnosis is crucial because proper treatment, whether conservative management or surgical reconstruction, leads to better outcomes. The ACL is crucial for knee stability, particularly during pivoting movements, and proper diagnosis ensures appropriate treatment to restore function and prevent further joint damage. MRI can diagnose the patterns and severity of bone marrow contusions that frequently have an association with the specific mechanisms of injury and can predict associated soft-tissue injuries, as reported by Song et al, as mentioned in the evidence 1.
From the Research
Diagnosis of ACL Injury
To diagnose an ACL injury, several physical examination tests can be used, including:
- Anterior drawer test
- Lachman test
- Pivot shift test
- Lever sign test
These tests can be used to evaluate the integrity of the ACL and diagnose injuries, with the Lachman test being the most accurate for detecting an ACL tear 2, 3.
Diagnostic Values of Physical Examination Tests
The diagnostic values of these tests have been compared in several studies, with the following results:
- The Lachman test is the most sensitive test for diagnosing chronic injuries of the ACL 3
- The pivot shift test is also sensitive, but its results can be influenced by several factors 3
- The Lever test has been shown to be effective in diagnosing ACL injuries, especially in patients with quadriceps atrophy 4
- The anterior drawer test is less sensitive than the Lachman test, but can still be useful in diagnosing ACL injuries 3
Use of Imaging Studies
In addition to physical examination tests, imaging studies such as magnetic resonance imaging (MRI) can be used to diagnose ACL injuries and identify concomitant injuries such as meniscal tears or bone contusions 2.
Diagnostic Algorithm
A diagnostic algorithm that combines multiple tests, including the Lachman test and pivot shift test, can improve diagnostic accuracy and help distinguish between partial and complete ACL tears 5.
Factors Affecting Diagnostic Accuracy
Several factors can affect the diagnostic accuracy of physical examination tests, including:
- Quadriceps atrophy, which can affect the results of the Lever test and anterior drawer test 4
- The phase of the injury (acute, subacute, or chronic), which can affect the results of the Lever test 4
- The presence of concomitant injuries, which can affect the results of physical examination tests and imaging studies 2