Posting for pronation and medial knee DJD

Members do not see these Ads. Sign Up.

Looking for opinions...I have a patient with the following MRI report: medial knee DJD, possible bone contusion of the medial tibial condyle, tear of her medial meniscus, and MCL sprain. Her pain is at her medial knee joint. (Surprise!) She also has a asymptomatic pronated foot on the same side. My gut feeling from working with her is that her pain is related mostly to her meniscus tear but I can't be sure. Lateral post to decrease compression on the medial side of the knee (but what about the MCL?) or medial post given the MCL and the pronated foot? Any thoughts? Thanks, Ann

 

Ann

Its still early days with all the biomechanical and clinical trials --- we had some discussion here:
http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=867

What I think the data will eventually show is that lateral wedging will generally only be helpful for medial knee OA if the range of eversion at the STJ is limited/restricted. This way the wedge will decrease the abductor moment (not necesarily alignment). If there is sufficient eversion at the STJ, the lateral wedge will simply pronate the STJ and internally rotate the tibia/knee and not necessarily change the abductor moment (a high abductor moment is possibly the main risk factor for medial knee OA) ....unfortunatly the data, so far is mixed on supporting this.

I am involved with a group of physiotherapists in a very big RCT on this - so far not one subject has reported an increase in foot or knee pain with lateral wedges (we did discuss this in the other thread).

In the RCT we are using a Formthoic Comfort brand prefab, that does give some medial longitudinal arch support, and add a lateral rearfoot and midfoot wedge to the bottom of that.

 

Ann,
Based on empirical evidence only..........

What influences the pain?
If it is made worse by weightbearing knee flexion, then a medial forefoot post should help.
The probable reasons for this are:
In many of this type of case I suspect a certain amount of internal rotation takes place at the femur, as well as the oft-quoted internal rotation which can take place at the lower leg. This all equates to an unstable limb which can cause transverse plane torque in the knee-joint.
In weightbearing, when the knee is flexed, the weight on the foot is transferred towards the forefoot. An extrinsic FF post of, say 2 or 3 degrees seems to stabilise the limb somewhat. You could try a piece of padding on the shoe, placed FF and medially to see if this helps, before actually putting a device in the shoe.

Clearly if there is meniscal damage , orthoses won't be of much use until this is tidied up.
Regards,
davidh

 

Thanks for your input Craig and David. Craig, your point about available calcaneal eversion and the effect of a lateral post is well taken. Just curious, would you expect the same point to hold true with a medial post? i.e. the effect at the knee would be minimal if there is adequate subtalar inversion available? Thanks, Ann

 

Fortunatly, in the age group we are talking about, most do seem to have restricted eversion, hence lateral wedges help the medial knee OA by going to end ROM of STJ to change moments.

When it comes to lateral knee OA and medial wedging, I have not been as happy with clinical results. I think that is becasue most still have a good range of inversion available, so the medial wedge just supinates the foot and external rotates the tibia/knee (which may be a good thing for aother reasons).... but is less likely to reduce the adductor moment at the knee unless the STJ is inverted to end range of motion ....I think...

 

I have had about equally good results both with orthoses with valgus wedging for medial knee OA and orthoses with varus wedging for lateral knee OA. Hovever, I also have no problem adding considerable medial heel skives and increased medial arch heights to the orthoses for patients with lateral knee OA. A varus shoe wedge alone without the conformity in the medial arch from a custom foot orthosis is generally not near as therapeutic as a varus-wedged, well-conforming foot orthosis in the treatment of lateral knee OA.

 

My "anecdotal" reaults for medial wedging and lateral knee OA have been mixed (not as good as lateral wedging for medial knee OA). The main risk factor for medial knee OA is an increased abductor moment which lateral wedging can reduce. I do not recall what the main risk factors for lateral knee OA are ...it may well be that its not an increased adductor moment ....

 

As the angle of genu valgum increases, there will be increased tendency for the lateral compartment of the knee to have increased interosseous compression forces and the medial collateral ligament of the knee to have increased tensile forces. The compression force exerted by the lateral femoral condyle vertically downward onto the lateral condyle of the tibia along with the tensile force from the medial collateral ligament acting vertically upward on the medial-superior tibia creates an internal knee adduction moment. It is this internal knee adduction moment that is necessary to mechanically counteract the external knee adbuction moment that results from the genu valgum deformity where the ground reaction force (GRF) acting on the plantar foot tends to "try to abduct the tibia relative to the femur".

Varus wedged orthoses will tend to decrease the external knee abduction moment since they act to shift the center of pressure on the plantar foot more medially, thus decreasing the tendency for GRF to "try to abduct the tibial relative to the femur". This decreased external knee abduction moment will also cause a decrease in internal knee adduction moment which results mechanically in a decrease in medial collateral ligament tensile force and a decrease in interosseous compression force in the lateral compartment of the knee.

Free body diagram analysis in this situation is invaluable in understanding the actions of the forces involved.

 

This is a great scenario and a great question.
As usual KK is on the money.


I think the point is what is the problem clinically, rather than radiologically? Many of us over-30's may have deplorable radiological findings in certain body areas, whilst failing to sense any symptoms.

Provide a valgus stress to the knee. If this reproduces the medial knee pain, you swing toward MCL. A provocative varus knee stress will send your diagnostic thoughts the other way toward the meniscus.

Applying a good Appley's test with (a) compression and (b) distraction will also assist with diagnosis. As will trialing the wedging that you speak of.



Very rarely will both structures be responsible for the symptoms. But in this event the knee will scream out for stability. Knee bracing and/or neutral posting may be an option here.

 

If you have confirmation of a meniscal tear, by delaying referal for surgery (providing your patient wants surgery) you are compromising the success of the surgery. If you want to stay on the right side of your orthopaedic community, get their opinion.

 

The meniscus tear was diagnosed by Orthopedics with the help of an MRI. It's not within my scope of practice as a PT to diagnose meniscus tears. The patient is trying to avoid surgery. Thanks for your input. Ann, PT