June 2017

OSTEOARTHRITIS: Studies explore mechanisms for distal knee OA therapies

By Jordana Bieze Foster

Studies presented in May at the 2017 ISPO World Congress in Cape Town, South Africa, added to knee experts’ understanding of the mechanisms underlying distal interventions to reduce pain and joint loading in patients with medial knee osteoarthritis (OA).

As patient compliance with traditional offloading knee braces remains largely suboptimal, clinicians who treat patients with medial knee OA are exploring the potential benefits of devices worn distal to the knee joint, which are less prone to migration and may be more discreet. These include a shoe with a series of grooves on the sole at major flexion points to mimic barefoot-like foot movement and an ankle foot orthosis (AFO) that shifts the center of pressure of the ground reaction force laterally.

Although the OA shoe has been associated with reductions in knee loading when averaged across study populations, research from the University of Central Lancashire in Preston, UK, suggests not all individuals respond positively to the intervention and that hip rotation strength and range of motion may help predict patient response.

Investigators assessed knee adduction moment (KAM) in 32 healthy volunteers as they walked under two conditions, wearing the OA shoes or standardized control shoes. The OA shoe was associated with a lower KAM than the control shoe, as expected, in most of the 64 knees; however, in 19 knees the KAM either increased or did not change in a clinically meaningful way.

The researchers found significant differences in hip internal/ external rotation and internal/external rotation strength between the responders and nonresponders, which suggests that hip-specific factors may be predictive of response, according to James Richards, PhD, a professor of biomechanics at the university, who presented the findings in Cape Town.

“This is a footwear intervention, but hip variables appear to determine responders versus nonresponders,” Richards said. “Now we need to see if the same is true in patients with knee OA.”

In a second ISPO presentation, researchers from Duderstadt, Germany-based Ottobock reported that an AFO designed for patients with knee OA compared favorably to a conventional offloading knee OA brace.

Investigators analyzed level walking gait in 28 patients with moderately severe knee OA (Kellgren-Lawrence grade 2-3); 16 wore knee braces and 12 wore AFOs. Reductions in pain were associated with both devices, but only in the AFO group was KAM with the device significantly lower than without. AFO use was also associated with a decrease in KAM in a 10-person control group.

In the AFO users, the tibia was more externally rotated with the device than without, and the center of pressure (COP) shifted laterally. This finding may help explain the mechanism involved, according to Thomas Schmalz, PhD, a biomechanist with Ottobock who presented the results in Cape Town.

“Since the AFO has no direct effect on the knee, it must be the COP shift that leads to the offloading,” Schmalz said.

Sources:

Richards J, Kim Y, Chohan A, et al. Can treatment response to a shoe designed for knee osteoarthritis be predicted from biomechanical and clinical measurements? Presented at the International Society of Prosthetics & Orthotics World Congress, Cape Town, South Africa, May 2017.

Shakoor N, Lidtke RH, Wimmer MA, et al. Improvement in knee loading after use of specialized footwear for knee osteoarthritis: results of a six-month pilot investigation. Arthritis Rheum 2013;65(5):1282-1289.

Schmalz T. Orthoses within the treatment of osteoarthritis of the knee: biomechanical comparison of KO and AFO principles regarding function and effect. Presented at the International Society of Prosthetics & Orthotics World Congress, Cape Town, South Africa, May 2017.

Menger B, Kannenberg A, Petersen W, et al. Effects of a novel foot-ankle orthosis in the nonoperative treatment of unicompartmental knee osteoarthritis. Arch Orthop Trauma Surg 2016;136(9):1281-1287

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