Question:medium
Which activity will be difficult to perform for a patient with an anterior cruciate deficient joint?
Which activity will be difficult to perform for a patient with an anterior cruciate deficient joint?
Show Hint
The ACL resists forward shift of the tibia; activities needing a strong quadriceps pull in a bent knee, like walking downhill, are hardest.
Updated On: Jul 8, 2026
- Walk downhill
- Walk uphill
- Sit cross leg
- Getting up from sitting
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Recall the job of the ACL.
The ACL keeps the shin bone from sliding forward on the thigh bone. Without it, that forward slide is unchecked.
Step 2: Think about the quadriceps and the tibia together.
Any time the quadriceps fires hard while the knee is bent, it pulls the tibia forward through the kneecap tendon. Walking downhill is exactly this situation, the knee stays bent and the quadriceps works eccentrically to slow the body down each step.
Step 3: See why that forward pull matters here.
In a normal knee the ACL absorbs this pull and keeps the joint steady. In an ACL deficient knee there is no brake, so the tibia jogs forward and the patient feels the knee buckle or give way.
Step 4: Compare with the other choices.
Uphill walking loads the hip more than the quadriceps. Sitting cross legged is a slow, low force movement. Standing up from sitting is controlled and does not carry the same sudden shear. None of these stress the ACL the way downhill walking does.
Step 5: State the answer.
$\text{Walk downhill}$ is the activity that becomes difficult after an ACL tear.
\[ \boxed{\text{Walk downhill}} \]
The ACL keeps the shin bone from sliding forward on the thigh bone. Without it, that forward slide is unchecked.
Step 2: Think about the quadriceps and the tibia together.
Any time the quadriceps fires hard while the knee is bent, it pulls the tibia forward through the kneecap tendon. Walking downhill is exactly this situation, the knee stays bent and the quadriceps works eccentrically to slow the body down each step.
Step 3: See why that forward pull matters here.
In a normal knee the ACL absorbs this pull and keeps the joint steady. In an ACL deficient knee there is no brake, so the tibia jogs forward and the patient feels the knee buckle or give way.
Step 4: Compare with the other choices.
Uphill walking loads the hip more than the quadriceps. Sitting cross legged is a slow, low force movement. Standing up from sitting is controlled and does not carry the same sudden shear. None of these stress the ACL the way downhill walking does.
Step 5: State the answer.
$\text{Walk downhill}$ is the activity that becomes difficult after an ACL tear.
\[ \boxed{\text{Walk downhill}} \]
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