EXTENDED REPORTS

The relationship between toe-out angle during gait and progression of medial tibiofemoral osteoarthritis

Alison Chang¹, Debra Hurwitz², Dorothy Dunlop⁴, Jing Song³, September Cahue³, Karen Hayes¹, Leena Sharma³

¹ Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
² Department of Orthopaedic Surgery, Rush-Presbyterian-St. Luke’s Medical Center, Chicago, IL, USA
³ Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
⁴ Institute for Healthcare Studies, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA

Leena Sharma, MD, Division of Rheumatology, Feinberg School of Medicine, Northwestern University, 240 E. Huron, Suite M300, Chicago, IL 60611, USA; L-Sharma{at}northwestern.edu

Background: A greater knee adduction moment increases risk of medial tibiofemoral osteoarthritis (OA) progression. Greater toe-out during gait shifts the ground reaction force vector closer to the centre of the knee, reducing the adduction moment. The present study was designed to test whether greater toe-out is associated with lower likelihood of medial OA progression.

Methods: Baseline assessments included: kinematic/kinetic gait parameters using an optoelectronic camera system, force platform and inverse dynamics to calculate three-dimensional external knee moments; toe-out angle (formed by the line connecting heel strike and toe-off plantar surface centres of pressure and the forward progression line; knee pain; and full-limb alignment. Knee x-rays (semi-flexed) were obtained at baseline and at 18 months, with progression noted as medial joint space grade worsening. With logistic regression, odds ratios (ORs) for progression/5° toe-out were estimated.

Results: In the 56 subjects (59% women, mean age 66.6 years, body mass index (BMI) 29), baseline toe-out angle was less in knees with than without progression (difference –4.4, 95% CI –8.5 to –0.3). Greater toe-out was associated with reduced likelihood of progression (OR 0.60, 95% CI 0.37 to 0.98). Adjusting for age, gender, BMI, pain severity and disease severity, the OR was 0.62, 95% CI 0.36 to 1.06. Adjusting for adduction moment (second peak), the OR was 0.72, 95% CI 0.40 to 1.28.

Conclusions: Osteoarthritic knees that progressed had less toeing-out than knees without progression. Greater toe-out was associated with a lower likelihood of progression. Adjustment for covariates did not alter the OR, although the 95% CI included 1. Further adjustment for adduction moment did alter the OR, consistent with the possibility that a mechanism of the effect may be via lowering of the adduction moment.

Abbreviations: BMI, body mass index; GRF, ground reaction force; K/L, Kellgren and Lawrence; MAK, Mechanical Factors in Arthritis of the Knee; NIAMS/NIA, National Institute of Arthritis and Musculoskeletal and Skin Diseases/National Institute on Aging; OA, osteoarthritis; OARSI, Osteoarthritis Research Society International; OR, odds ratio

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