Question:medium
What would be the most reliable test for an acutely injured knee of a 27-year-old athlete?
What would be the most reliable test for an acutely injured knee of a 27-year-old athlete?
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In an acute knee injury, swelling and hamstring spasm block full flexion, so the low-flexion Lachman test outperforms the anterior drawer test.
Updated On: Jul 8, 2026
- Anterior drawer test
- Posterior drawer test
- Lachman test
- Steinmann test
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: Picture the injured knee right after the accident.
A 27 year old athlete with a fresh knee injury most likely has torn the ACL. Right after the injury the joint fills with blood and the muscles around it tighten up on their own to guard the joint.
Step 2: Think about what each test needs from the knee.
The anterior drawer test needs the knee flexed all the way to $90$ degrees before the tibia is pulled forward. A swollen, guarded knee usually cannot bend that far without real pain, so the test becomes hard to perform and easy to read wrong.
Step 3: See why the Lachman test avoids that problem.
The Lachman test only needs a slight bend, around $20$ to $30$ degrees, which a swollen knee can usually tolerate. Because the hamstrings are less able to guard the joint at this smaller angle, the true amount of forward slide of the tibia shows up more clearly. This is why it stays accurate even in a freshly injured knee.
Step 4: Set aside the wrong options.
The posterior drawer test looks for a posterior cruciate tear, which is a different ligament and different injury pattern. The Steinmann test is a provocation test for a torn meniscus, not for ligament laxity, so it does not answer the question about ligament injury reliability.
Step 5: State the conclusion.
For an acutely injured knee, the Lachman test is the more reliable choice over the anterior drawer test, because it works around the pain and spasm that block a full 90 degree flexion right after injury.
\[ \boxed{\text{Lachman test}} \]
A 27 year old athlete with a fresh knee injury most likely has torn the ACL. Right after the injury the joint fills with blood and the muscles around it tighten up on their own to guard the joint.
Step 2: Think about what each test needs from the knee.
The anterior drawer test needs the knee flexed all the way to $90$ degrees before the tibia is pulled forward. A swollen, guarded knee usually cannot bend that far without real pain, so the test becomes hard to perform and easy to read wrong.
Step 3: See why the Lachman test avoids that problem.
The Lachman test only needs a slight bend, around $20$ to $30$ degrees, which a swollen knee can usually tolerate. Because the hamstrings are less able to guard the joint at this smaller angle, the true amount of forward slide of the tibia shows up more clearly. This is why it stays accurate even in a freshly injured knee.
Step 4: Set aside the wrong options.
The posterior drawer test looks for a posterior cruciate tear, which is a different ligament and different injury pattern. The Steinmann test is a provocation test for a torn meniscus, not for ligament laxity, so it does not answer the question about ligament injury reliability.
Step 5: State the conclusion.
For an acutely injured knee, the Lachman test is the more reliable choice over the anterior drawer test, because it works around the pain and spasm that block a full 90 degree flexion right after injury.
\[ \boxed{\text{Lachman test}} \]
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