Background/Purpose: No strategies have been shown to prevent Medial knee osteoarthritis (MKOA).  For those with symptomatic unilateral MKOA, the contralateral knee may be at risk for developing MKOA.  Early adaptation of load reducing strategies may reduce the development of the disease in the contralateral knee. 

Methods:

90 subjects (69F 21M, Age 60±8, BMI 28.3±4.0) with radiographic and symptomatic medial knee OA (K-L grade 2-3, ambulatory pain >30 mm on a 100 mm VAS) were randomized into a control group fitted with bilateral neutral foot orthosis or a treatment group fitted with 7 degree valgus posted foot orthosis.  The knee joint with greater pain was labeled as the index side.  Subjects underwent gait analyses using an optoelectronic camera system and multi-component force plate. Subjects walked at their normal speed, and comparisons were performed after matching for speed. The peak external knee Adduction Moment (KAddM) (%body weight * height, %BW*Ht) was calculated and used as the primary endpoint. Subjects were evaluated at baseline and again at 36 months with and without the orthosis.  Changes in the peak KAddM between conditions and time variable were calculated and expressed as a percentage change in the control condition.  Nonparametric confidence intervals were calculated with the binomial method around the percentage of change to assess statistical significance with significance set at p<0.05.

Results:

After 3 years the contralateral knee showed a 5.01±0.09% (Median±IQR) increase in medial knee load when the control orthosis was added while there was a (-)5.29±0.72% (Median±IQR) decrease in the medial knee load with the addition of the wedge orthosis in the treatment group.  In the wedge treatment group the median drop in knee adduction moments between baseline and 36 months was (-)7.61±0.84% in the contralateral knee and (-)6.49±0.13% on the index side (Median±IQR).  Interestingly After 3 years in the control treatment group there was a 10.66±0.52%  increase in the medial knee loads on the index side while there was a (-)11.29±0.74%  decrease in the medial knee loads on the contralateral side (Median±IQR).

Conclusion:

The contralateral knee may be at risk in subjects with MKOA.  These data suggest that the contralateral knee may get better benefit using load reducing strategies such as valgus wedge foot orthosis.  The greatest sustained reduction of knee loads was seen in the contralateral knee of the control group.  Since the control group was wearing custom foot orthosis posted to perpendicular to the ground it may be that a non-valgus posted custom foot orthosis on the contralateral side may be of benefit for reducing the progression of knee osteoarthritis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/reducing-loads-in-the-contralateral-side-in-medial-knee-osteoarthritis-a-3-year-follow-up-study/