Varus/Valgus Stress

[seminoma]

Could one of you fine ortho guys (or gals) clarify the concept of varus/valgus for me? I posted this in the step 1 forum as well, but I figure ortho probably knows best.

In the MCL test (abnormal passive abduction) you are exerting a medially directed (laterally originating) force, which (if MCL is injured) will result a valgus deformity (i.e. knee moves medially and distal tib/fib move laterally). So the force originates laterally, but pushes medially.. which is considered a valgus force.

In the LCL test (abnormal passive adduction) you are exerting a laterally directed (medially originating) force, which will result in a varus deformity (i.e. knee moves laterally, distal tib/fib moves medially). So the force originates medially, but pushes laterally.. which is a varus force.

LCL injury --> varus deformity (bow legged) resulting from a medial originating force.
MCL injury --> valgus deformity (knock knee) resulting from a lateral originating force.

So basically varus "deformity" and varus "force" are in opposite directions (same for valgus force/deformity)?

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[hanky1982]

No. So a varus deformity means that the leg is in varus. Ie the knee is in varus. The force is what we use to determine where the force is coming from. A varus force is a force the is directed laterally at the knee (could be a push from the medial side or a pull from the lateral side). It is just the vector in which the force is going. The deformity is the resultant alignment of the limb.

So if there is a lax/torn LCL, a varus force will enhance the varus of the knee. The resultant deformity after the injury is a varus knee because the check reign of the LCL isn't there so it opens up on the lateral side creating a varus knee.

Hope that makes sense. You are talking about two different things. Force =vector, deformity =alignment.

 

[seminoma]

No. So a varus deformity means that the leg is in varus. Ie the knee is in varus. The force is what we use to determine where the force is coming from. A varus force is a force the is directed laterally at the knee (could be a push from the medial side or a pull from the lateral side). It is just the vector in which the force is going. The deformity is the resultant alignment of the limb.

So if there is a lax/torn LCL, a varus force will enhance the varus of the knee. The resultant deformity after the injury is a varus knee because the check reign of the LCL isn't there so it opens up on the lateral side creating a varus knee.

Hope that makes sense. You are talking about two different things. Force =vector, deformity =alignment.

Cool, I think it makes sense now.

So when First Aid says "medial (varus) force --> lateral space widening of tibia --> LCL injury" they're saying that you push from the medial side?

And "lateral (valgus) force --> medial space widening of the tibia --> MCL injury" means you push from the lateral side?

 

[massmocha]

Cool, I think it makes sense now.

So when First Aid says "medial (varus) force --> lateral space widening of tibia --> LCL injury" they're saying that you push from the medial side?

And "lateral (valgus) force --> medial space widening of the tibia --> MCL injury" means you push from the lateral side?

Think of holding the knee stable with one hand and applying the force to the tibia:
vaLgus is Lateral force to the tibia and opens the medial space. If MCL is injured there is no check on medial space opening and you have excess laxity relative to the uninjured side.
varus is medial force to the tibia and opens the lateral space. If LCL is injured there is no check on lateral space opening and you have excess laxity relative to the uninjured side.

 

[hanky1982]

Cool, I think it makes sense now.

So when First Aid says "medial (varus) force --> lateral space widening of tibia --> LCL injury" they're saying that you push from the medial side?

And "lateral (valgus) force --> medial space widening of the tibia --> MCL injury" means you push from the lateral side?

Yes

 

[seminoma]

Thanks all, thinking about holding the knee and applying force to the tibia makes it much more clear.

 

[Orthojoe]

i always think of varus/valgus as directed toward midline... Varus is the distal portion of the affectd limb (bone, etc) goes toward midline and valgus is the the affected limb goes away from midline. you can apply that concept to near every part of the body. your force vector is was allows that movement.