VICTORIA, Australia—Increased medial knee loading is associated with worsened progression of knee osteoarthritis (OA), and wearing shoes increases this joint stress, according to Georgina Kemp, BAppSc, and colleagues from the University of Melbourne in Victoria, Australia. The researchers report in Arthritis Care & Research that using a cane also significantly reduces medial knee loading in OA patients.¹

The Australian researchers studied 40 patients with medial knee OA using 3-dimensional gait analysis to measure peak knee adduction moment, which is an indicator of medial knee joint load. The joint load was compared with patients walking barefoot versus wearing their usual shoes. Joint load was also measured in 20 patients while walking with a cane in the contralateral hand to the affected knee versus while walking unaided.

The analysis showed that wearing shoes significantly increased medial knee joint load by 7.4% compared with walking barefoot (mean knee adduction moment 3.77 vs 3.49, P <.001) and that using a cane decreased medial knee loading by about 10% (mean knee adduction moment 3.38 vs 3.76, P = .001). The latter finding suggests that early use of a cane “has the potential to reduce the risk of disease progression in knee OA,” the authors wrote.

Kemp notes that an increase of 1 unit of peak knee adduction moment produces a 6.5-fold increase in the risk of progression of knee OA. She concludes, “[I]t is possible that wearing shoes may increase the risk of knee OA progression by a factor of 2.8 on average.

Furthermore, several individuals demonstrated increases of >20%, which may increase their risk of disease progression >6-fold. Because it is potentially dangerous as well as impractical to advise patients with knee OA to walk about in bare feet, further research is needed to determine which types of shoes least increase the knee adduction moment (or, ideally, reduce it) and to evaluate the effect of wearing shoes on long-term disease progression.”

Translating research into practice

Najia Shakoor, MD, and Joel A. Block, MD, at Rush Medical College in Chicago reported similar observations about the effects of walking barefoot versus shoes and have also studied the effects of different types of shoes.² Dr. Shakoor told MSKreport that the Kemp study adds important supporting evidence.

Dr. Shakoor’s studies have actually led her research group into the shoe business. They are currently conducting a pilot study in 50 patients with medial compartment knee OA and no other affected joints. Patients are randomized to one of three shoe designs: a flat shoe with a very flexible sole, a flat shoe with a stiffer sole, and a conventional cushioned support shoe.

“The flat, flexible shoe design is patented, and the shoes are being handmade for us at the moment, but we expect to have them produced in a factory in China eventually,” Dr. Shakoor said. Pilot study endpoints are pain and joint loading, and the two shoe designs that are most effective will then be compared in a 160-patient randomized trial.

“Finding that walking barefoot was less stressful for the arthritic knee than walking in the cushioned support shoes, which we had all be recommending, was a surprise for everyone,” Dr. Sakoor said. “It did point to an area of conventional belief among clinicians that had no real research support. In contrast, we now know that, at least in the short term, it is possible to substantially change the load our knees experience by changing shoes, and there is anecdotal evidence that higher knee loading is associated with more pain and OA progression. All of this needs study over the long-term in people wearing different types of shoes. These data really show us that we haven’t looked at shoes carefully enough.”

References

1. Kemp G, Crossley KM, Wrigley TV, et al. Reducing joint loading in medial knee osteoarthritis: shoes and canes. Arthritis Care Res. 2008;59:609-614.
2. Shakoor N, Block JA. Walking barefoot decreases loading on the lower extremity joints in knee osteoarthritis. Arthritis Rheum. 2008;54:2923-2927.