|
Year |
2005 |
|---|---|
|
Question Number |
96 |
|
Category |
Sports Medicine |
Question
Which of the following exercises generally is not allowed in the 1st 6 weeks of rehabilitation after reconstruction of the ACL?
1. Open chain extension
2. Open chain flexion
3. Closed chain extension
4. Closed chain flexion
5. Active-assisted range of motion
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Answer (click for answer)
The correct answer is 1.
The reason to prohibit a particular activity after an ACL reconstruction would be to avoid excessive strain on the graft. You need to understand the rehab terms, and if so, this question is easy.
Open chain exercises are those that involve a free terminal appendage. An example would be active extension of the knee with the patient seated on a table with the legs dangling. Because there is no normal force distally, there are little compressive forces involved at the level of the joint. Rather, these exercises tend to involve more shear forces at the level of the joint. How this works is works is that the quad pulls on the tibial tubercle, pulling the tibia forward (like an anterior drawer test). Anterior translation (shear force parallel to the joint surface) is stopped by the intrarticular structures (ACL, posterior capsule, etc), normalizing the translation, and thus further pull on the tubercle leads to rotation (knee extension) rather than translation, which has equilibrated.
Closed chain exercises are those which involve an appendage distally fixed. An example would be standing from a squatted position. As with the previous example, the knee is extending, but since there is now a distally applied normal force (the ground), what results is primarily compression at the joint level (ie force directed perpendicular to the jointline).
There is no reason to prohibit active-assisted ROM after an ACL reconstruction as it is relatively stable. Of the remaining 4 answers, closed chain exercises are eliminated as compressive forces at the knee would not stress the graft. Open chain activities involve stresses parallel to the joint and as such, could stress the graft. Since knee extension involves an anterior translation force at the tibia (like an anterior drawer) and knee flexion involves an posterior translation force at the tibia (like an posterior drawer), it would make sense that open chain knee extension exercises would put the most stress on the graft.
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