Effects of Toe-out Gait Modification on Clinical and Biomechanical Measures in People With Knee Osteoarthritis
Phase: NA
Conditions: Knee Osteoarthritis
Sponsor: University of British Columbia

Official Title:  
Effects of Toe-out Gait Modification on Clinical and Biomechanical 
Measures in People with Knee Osteoarthritis 
NCT Number: 
NCT02019108 
Document Date:  November 25, 2013 
 

Methods 
 
Participants 
 
Community-dwelling individuals were recruited via an existing laboratory database as well as 
advertisements in print media. Inclusion criteria were: (i) definitive medial tibiofemoral 
osteophytes on x-ray; (ii) joint space narrowing greater in the medial tibiofemoral compartment 
compared to the lateral compartment; (iii) history of knee pain longer than six months; and (iv) 
average knee pain of at least 3 out of 10 over the one month period prior to initial screening. 
Exclusion criteria were: (i) knee surgery or intra-articular pain relief injection within six months; 
(ii) current or past (within six months) oral corticosteroid use; (iii) history of knee joint 
replacement or tibial osteotomy; (iv) any other condition affecting lower limb function; (v) 
participation in a new structured exercise program within the past three months, or planning to 
commence exercise or other treatment for knee OA in the next four months; and, (vi) an inability 
to travel to the university to attend testing and training sessions. The study was approved by the 
Institution’s Clinical Research Ethics Board and all participants provided written informed 
consent. 
 
Sample size was determined based on randomization with stratification, and covarying for 
baseline values in the statistical analysis. Using effect size estimates of 0.8 for WOMAC pain 
and 1.0 for KAM impulse, based on pilot data using a similar design, it was determined that  
participants in each group was required to attain 90% power to detect significant differences in 
pain and KAM outcomes between groups with an alpha of 0.05. Using a conservative estimate of 
10% attrition, the aim was to recruit 73 participants for this study. 
 
Study Design 
 
This was a parallel group, assessor-blinded, randomized controlled trial. Interested participants 
were initially screened for inclusion and exclusion criteria over the telephone and eligible 
individuals then underwent a physical screen. Screening was overseen by a researcher not 
involved in data collection or analysis. 
 
This physical screen was conducted to confirm the presence of knee pain, and to perform a 
preliminary walking assessment to assess self-selected foot progression angle. Participants 
performed three trials of self-selected, over ground walking while three reflective skin markers 
tracked the movement of the sacrum, the second toe, and posterior calcaneus of the study limb 
(defined as the self-declared osteoarthritic limb in those with unilateral symptoms, or the most 
painful limb in the case of bilateral symptoms). The mean foot progression angle across the three 
trials was calculated. As the goal of the toe-out modification program was to increase the self-
selected, baseline foot progression angle by 15° in the toe-out direction, 15° of toe-out at the 
physical screening was selected as the threshold. This was done due to (i) the difficulty in 
achieving toe-out angles of 30° by people with knee OA, and (ii) the fact that those who already 
exhibit large amounts of toe-out would likely not be candidates for toe-out gait modification in 
the clinical setting. 
 

Those who passed physical screening were referred for radiographic evaluation. Standing, semi-
flexed, postero-anterior radiographs were obtained and graded for disease severity using the 
Kellgren and Lawrence (KL) OA classification system. 
 
Individuals who met the radiographic criteria listed above were invited to the laboratory for a 
baseline (Week 0) testing session where self-report questionnaire, objective physical function, 
and biomechanical data were collected. Following completion of baseline testing, the 
randomization procedure was conducted by a study biostatistician who was not involved in any 
aspect of data collection or training. Randomization was initiated by the study research 
coordinator, who provided the biostatistician with each participant’s study ID, sex, and KL 
grade. The biostatistician then responded via email with the group allocation, and maintained the 
randomization parameters and list offsite. Group allocations were determined prior to study 
commencement, and randomization was stratified by sex (male, female) and disease severity 
(mild or moderate grouped together, severe). 
 
Participants returned to the university the following week (Week 1) to begin their training 
program, and were informed of their group allocation at this time. Each home-based program 
lasted four months and was supplemented with eight training sessions with the study trainer at 
Weeks 1, 2, 4, 6, 8, 10, 12 and 15 of the intervention, with typical sessions lasting 20 minutes in 
Week 1 and increasing to 40 minutes by Week 15. All training sessions, regardless of group 
allocation, were conducted by the same trainer in the same rehabilitation gymnasium. The first 
training session for each participant was always a one-on-one session with the trainer, with 
subsequent sessions conducted in groups of one to three individuals; in cases of group sessions, 
only individuals from the same group allocation were present in the gymnasium to prevent cross-
contamination of groups. 
 
Follow-up testing occurred four months after baseline testing, with a final retention testing 
session conducted one month later. The same outcome measures, completed in the same testing 
order, and by the same blinded assessor, were collected at each testing session. No training or 
instructions of any kind were provided between these final two testing sessions. 
 
Interventions 
 
For both groups, the intent was to increase the weekly amount of walking out in the community 
by 40% over and above that exhibited prior to enrollment. Initial values were assessed via 
discussion with participants at the first training session, and prescribed weekly increases were 
determined individually at each training session in consultation with the trainer. 
 
Toe-out (TO) gait modification program 
 
Participants randomized to the TO program were trained to perform walking with 15° more toe-
out than the self-selected amount measured at the baseline testing session. Our previous pilot 
study showed modest improvements of 6.7° in self-selected toe-out angle following 10-weeks of 
toe-out gait retraining intending to increase toe-out by 10°, that resulted in marginally 
statistically significant improvements in late stance KAM (p=0.04) and self-reported pain 

(p=0.02), and non-significant decreases in KAM impulse (p=0.20). Thus, a larger toe-out 
increase was selected for this study. 
 
Toe-out modification during the training sessions was facilitated with mirror-guided biofeedback 
of performance. Participants placed their study foot on a protractor device at the target toe-out 
angle for that session, and verbally instructed the therapist in the placement of a piece of green 
tape on the mirror to best cover the reflection of the foot in this target position. The tape 
remained on the mirror during the training session to guide foot placement during treadmill 
walking. To promote motor learning, a faded feedback paradigm was used with removal of real-
time biofeedback commencing at session 4 (mean percentage of walking time with feedback: 
Week 6 = 90%; Week 8 = 75%; Week 10 = 60%; Week 12 = 45%; Week 15 = 35%). Self-
reported difficulty in achieving the target angle was recorded at each training session using an 
11-point numerical rating scale (NRS) with terminal descriptors of 0 = “no difficulty” and 10 = 
“unable to perform”). Participants were instructed to maintain the increased toe-out angle outside 
the training sessions whilst walking in the community. 
 
Progressive walking (PW) program 
 
Participants randomized to the PW program underwent all training procedures as those in the TO 
group, with the exception of receiving no training or instruction related to toe-out walking. This 
included walking on the treadmill in front of a mirror during training sessions, but without foot 
placement guide tape as per the TO training protocol. 
 
Outcome measures 
 
Pain and physical function 
 
At each testing session, participants completed the Western Ontario and McMaster Universities 
Arthritis Index (WOMAC) Likert version22. Average knee pain over the previous week was also 
assessed using an 11-point NRS with terminal descriptors of 0 = “no pain” and 10 = “worst pain 
imaginable”. Overall perceived change at follow-up compared to baseline was assessed using a 
15-point Likert scale (-7 = “a very great deal worse” 0 = “about the same”, +7 = “a very great 
deal better”). Finally, participants completed the timed stair climb test where they were 
instructed to ascend 12 stairs “as quickly as possible”, and the fastest time from the two attempts 
was recorded. 
 
Gait biomechanics 
 
Gait data were recorded for barefoot, over ground walking trials at a self-selected speed. Twenty-
two retro-reflective markers were affixed to the participant according to a modified Helen Hayes 
marker set, and their movements were captured using twelve high-speed digital cameras (Motion 
Analysis Corp., Santa Rosa, CA) sampling at 100 Hz. An initial standing static trial was 
collected using additional markers placed over the medial malleoli and femoral epicondyles to 
determine segment orientations and joint centres of rotation. Kinematic data from the cameras 
were synchronized with two force platforms (OR6-6, Advanced Mechanical Technologies Inc.) 
visually concealed in the floor of a 10m walkway and sampling data at 2000 Hz. Participants 

were provided no instructions pertaining to walking mechanics during any of the gait 
assessments. 
 
Inverse dynamics techniques and commercially available software (Orthotrak, Motion Analysis 
Corp.) were used to calculate gait variables including: KAM (early stance peak, late stance peak, 
impulse), peak external knee flexion moment (KFM) during stance, and mean foot progression 
angle during foot-flat (positive values = toe-in orientation, negative values = toe-out orientation). 
The mean value from five walking trials was calculated for each biomechanical variable. 
 
Adherence, concurrent treatments, and adverse events during interventions 
 
Adherence to both training programs was assessed as the total number of supervised walking 
sessions attended for each participant. Compliance with the prescribed walking increases was 
obtained from log book data completed by participants detailing their daily amount of walking 
for the duration of the study, and weekly totals (in hours) were calculated. Additionally, an 11-
point NRS (0 = “not confident at all”, 10 = “very confident”) in the log book was used to assess 
self-reported confidence in the ability of those in the TO group to maintain the increased toe-out 
angle whilst walking in the community. Finally, concurrent treatments and adverse events 
reported during the intervention were assessed using open-ended questions in the log book 
maintained by the participants. For the purposes of analysis, adverse events were defined as 
those lasting longer than two weeks in duration, or requiring additional treatment. 
 
Statistical analysis 
 
The primary outcomes were WOMAC pain, KAM impulse, and foot progression angle, and the 
primary endpoint was the follow-up assessment. All other biomechanical and clinical outcomes 
were considered secondary in nature. Between-group comparisons were the primary analyses, 
with within-group comparisons used for informational purposes. Analysis of covariance 
(ANCOVA) models were fit predicting each outcome variable evaluated at both time points 
(follow-up and retention), with group as predictor, and while controlling for baseline values. For 
biomechanical outcomes (knee adduction and flexion moments, as well as foot progression 
angle), additional models were computed while additionally controlling for concurrent gait speed 
at the associated time point (follow-up or retention). For baseline data, crude means were 
computed. Adjusted least squares means (LS means) with standard errors and 95% confidence 
intervals were computed for each group at both follow-up and retention. Adjusted LS means 
were computed in similar models for within-group (delta) scores. Finally, model-adjusted group 
effects were computed, along with p-values and 95% confidence intervals, for all outcomes. 
 
All data were analyzed using an intention-to-treat analysis, and the primary analyses assumed 
that data were missing completely at random (MCAR). In sensitivity analyses, multiple 
imputation was performed as per the methods described by van Buuren. Results and conclusions 
were compared to the MCAR analysis, and any differences noted. All statistical analyses were 
conducted by a biostatistician blinded to group allocation and who was not involved in any other 
aspect of the study. Analyses were performed using SAS v9.4 (SAS Institute, Cary, North 
Carolina).