Use of a medial unloader knee brace to alter knee alignment – implications for knee osteoarthritis treatment

This week’s EXSS Impact post was developed by FJ Goodwin, who is a PhD student in the Human Movement Science Curriculum being mentored by Dr. Troy Blackburn.  Many thanks to FJ and Troy for providing this week’s EXSS Impact material.

Why did you do this study?

Knee osteoarthritis (KOA) is a degenerative joint disease which affects the tibiofemoral joint leading to significant pain and disability. KOA most commonly affects the medial compartment of the tibiofemoral joint compared to the lateral compartment. KOA has a direct medical cost of $165 billion per year. Those who suffer traumatic knee injuries (e.g. meniscus tears) are at an increased risk to develop KOA. There is currently no cure for KOA, only palliative measures to reduce pain or attempt to slow disease progression. Once the disease has significantly progressed, the most common solution is knee joint replacement surgery.

kneevarusIn an attempt to improve mobility in patients with KOA, medial unloader braces are prescribed to help unload the medial tibiofemoral joint during walking by placing a valgus force on the outside of the knee. In short, valgus position is more “knock-kneed” whereas varus position is more “bow-legged”. By utilizing 3 point bending, this brace serves to “open” the medial compartment and reduce load on experienced at the medial compartment. A lateral heel wedge can also be prescribed to act on the foot and have effects at the knee by working up the kinetic chain.

FJ1

(A) Medial unloader knee brace and (B) and lateral heel wedge

These orthotic devices potentially reduce pain and improve mobility in patients with KOA. However these braces and other orthotics are often given to patients who already have KOA or possess a varus alignment at the knee. The purpose of this study was to analyze the effect of medial unloader braces and lateral heel wedges on young healthy adults with neutral knee alignments. This population represents the knee structure of subjects who may have experienced a traumatic knee injury/surgery without the typical resultant joint structure changes (i.e. a subject who has undergone a meniscus tear who is act higher risk for KOA development)

What did you do and what did you find in this study?

FJ2

Frontal plane knee position at heel strike.  Negative value indicates valgus position.

We analyzed subjects during normal walking in four different conditions: control (no orthotics), brace at 50% maximum load, brace at 100% maximum load, lateral heel wedge. They were briefly acclimated to each condition prior to the data collection. We looked at frontal plane knee angle at heelstrike, peak frontal plane varus angle, peak knee internal valgus moment and frontal plane angular impulse. Frontal plane knee angle at heelstrike was the only statistically significant finding from this study. The unloader brace at 50% maximum load (-2.04° ± 3.53°) and 100% max load (-1.80° ± 3.63°) placed the knee is a more valgus position at heelstrike compared to the lateral wedge condition (-0.05° ± 2.85°) (Figure 2). Although we observed a significantly different frontal plane knee joint angle at heelstrike we feel these orthotics were not effective in altering knee function. The difference in frontal plane knee angle was within 2 degrees which is not clinically relevant amount of change.

How do these findings impact the public?

This study suggests that the orthotics tested in this study were not effective in altering knee function in a clinically relevant manner. Previous studies have used more aggressive braces with larger correction ability that may provide more medial unloading capability in subjects. These orthotics have shown to be effective in subjects with KOA and further studies need to be completed to analyze the potential benefits for subjects without KOA.

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