The Effects of Protonics Knee Brace Versus Hamstring Resisted Exercise on Individuals With Patellofemoral Pain Syndrome
Phase: NA
Conditions: Patellofemoral Pain Syndrome
Sponsor: Loma Linda University

1 
 
 
 
 
 
 
 
 
 
 
 
Protonics Knee Brace versus Hamstring Resisted Exercise (HRE) 
on Individuals With Patellofemoral Pain Syndrome 
 
 
01/11/2017 
 
NCT03042559 
 
IRB #: 5160417 
 
 
 

2 
 
Methodology 
Design 
This study is a randomized controlled trial with two treatment groups – the ProtonicsTM 
knee brace group and the sport cord group. Subjects with PFPS were asked to complete a series 
of open-chain hamstring resistance exercises with either apparatus, for which the procedures are 
described below, for four weeks. After the intervention, knee joint function and clinical 
symptoms of PFPS were assessed and compared between groups. 
Participants 
Subjects were recruited based on the following inclusion criteria: male or female18-45 
years of age; has exhibited patellofemoral pain symptoms for more than 1 month and have a pain 
level ≥ 3 on the NPRS; has experienced pain during at least 2 functional activities, such as 
squatting, ascending/descending stairs, and/or running. Individuals who had experienced traumatic 
injuries to the knee joint or lower extremity, displayed signs or symptoms of a meniscus lesion or 
ligamentous-related pathology, had been diagnosed with a neurological disorder, diabetes, 
osteoarthritis, osteoporosis, or rheumatoid arthritis, or reported taking any over-the-counter pain 
medications during the study period were excluded from the study. Screening of subjects was done 
by a licensed physical therapist under the supervision of an Orthopedic Clinical Specialist (OCS) 
with over 29 years of experience. 
Flyers, emails, phone calls, and referrals were used to gather a convenience sample of 
subjects. Subjects were randomly assigned to either the ProtonicsTM knee brace group or the sport 
cord group using simple randomization (Figure 1). All participants were required to sign an 
informed consent form. This study was approved by the Loma Linda University Institutional 
Review Board and was registered at http://clinicaltrials.gov (registration number NCT03042559). 

3 
 
Procedures 
 
Subjects assigned to the ProtonicsTM knee brace group were asked to perform warm up 
exercises, followed by specific therapeutic exercises that are part of the Protonic Therapy Program 
(PTP)18. The Protonics system  has been introduced to physical therapists as a potential treatment 
for PFPS. The system includes a brace set to resist knee flexion and a set of specific exercises to 
perform daily. Through resistance to knee flexion, the system is advertised to decrease retropatellar 
contact pressure due to changes in pelvis inclination and available hip rotation. Specifically, 
resistance to knee flexion is purported to increase hamstring activity and inhibit the activity of the 
tensor fasciae latae and psoas muscles. The manufacturer asserts that prolonged use of the system 
results in greater hamstring activation, which leads to permanent structural changes through 
reciprocal inhibition at the hip and pelvis18. The phases of the intervention are summarized in Table 
1. The warm-up consisted of the subject wearing the ProtonicsTM knee brace set at a moderate 
resistance level and flexing the knees while sitting, standing, and reclining in the supine and prone 
positions. The exercises, were done in sets of 10-15 repetitions, 3 sets per day, 3 times per week, 
for 4 weeks. Each set took about 5 minutes for subjects to complete, or 15 minutes per day.  
The PTP has three phases. At the start of each phase, subjects were given detailed 
instructions on how to perform the warm up and therapeutic exercises and instructed to perform 
them at home 3 times per week. During Phase I or day 1, subjects were asked to walk for 5 minutes 
or as tolerated at varying speeds while wearing the brace. Subjects also performed the ProtonicsTM 
gait and ProtonicsTM neuromuscular repositioning techniques. During Phase II or weeks 1 and 2, 
subjects performed the same ProtonicsTM techniques, and were asked to walk for 8 minutes or as 
tolerated at varying speeds and inclines. Subjects were also instructed to perform 10-15 repetitions 
of the hamstring curl in the prone, supine, and seated positions at home. The seated hamstring curl 

4 
 
is displayed in Figure 2. During Phase III or weeks 3 and 4, subjects were once again asked to 
perform the aforementioned ProtonicsTM techniques, but this time they were also asked to walk 
forwards and backwards at varying speeds and inclines for 10 minutes or as tolerated. They were 
also instructed to do 10-15 repetitions of the standing hamstring curl.  
Subjects assigned to the sport cord group were asked to do the same warm-ups and 
exercises using the sport cord in the supine, standing, sitting, and prone positions. The prone 
hamstring curl can be seen in Figure 3. The only difference is that subjects were asked to only 
walk backwards instead of forwards in order to avoid activation of the hip flexor muscle. The 
appropriate level of resistance for each subject was calculated by multiplying their weight in 
pounds by 0.3. Subjects were then given either light, medium, or heavy resistance cords according 
to the following classification scheme: light (pink color) with resistance 3 (R3), 0-30 lbs.; medium 
(orange color) with resistance 5 (R5) 0-50 lbs.; heavy (yellow color) with resistance 7 (R7) 0-70 
lbs. All subjects completed three study visits, and a total of four measurements were taken at 
baseline, immediately following the first session, at two weeks, and at 4 weeks. 
Compliance 
Several methods were employed to maximize subjects’ compliance: During the initial visit, 
subjects were provided a thorough educational session on the appropriate use of the sport cord and 
knee brace and were given the opportunity to ask questions at any point of the study. The 
educational session included oral instructions as well as brochures which subjects could refer to 
for complete written instructions and visual depictions of the prescribed exercises.  As the study 
was divided into three phases, subjects were asked to visit the lab at least three times and to return 
for additional visits if they wished. Additionally, a log sheet was filled out by each subject to track 

5 
 
completion of his/her exercises at home. Finally, text message reminders were sent to each subject 
throughout the study.  
Outcome Measures 
The primary outcome measures of the study can be divided into two categories: clinical 
outcomes and functional outcomes.  
Clinical Outcome Measures: 
APT was assessed using a palpation meter (PALM) inclinometer with the subject in the 
standing position; one arm of the caliper was placed on the anterior superior iliac spine (ASIS) 
while the other was positioned on the posterior superior iliac spine (PSIS). This technique was 
shown to be a reliable way of assessing sagittal pelvic position 19. As described by Herrington, 
subjects were required to stand on a 30 centimeter high platform, look forward at a fixed point, 
and keep their arms crossed over their chest during palpation 20.  
Hip internal/external rotation active range of motion (ROM) was measured from sitting 
position as follows: the measured hip was placed at 90 degrees flexion, in neutral position between 
adduction and abduction, and knee joint at 90 degrees flexion, as described by Han and colleagues 
21. While the contralateral hip placed on 30 degrees abduction. Using a fluid-filled inclinometer 
placed parallel to the shaft of distal tibia and proximal to medial malleolus. The tibia was vertically 
aligned at starting position and then the inclinometer was calibrated to zero 22.  
Iliotibial band flexibility was measured using a modified version of the Ober’s test in which 
an inclinometer was placed at the distal lateral thigh. In which, zero degree was recorded when 
thigh was horizontal, positive value was recorded if the thigh was abducted, and a negative value 
was recorded if the thigh was adducted past horizontal 23,24. 
Functional Outcome Measures 

6 
 
Patient satisfaction was measured using the GROC scales, which is a commonly used 
method for quantifying subjects’ self-perceived progress or decline over time. The GROC is scored 
on 15-point numerical scale from -7 to +7 where -7 represents “a very great deal worse,” 0 
represents “about the same” and +7 represents “a very great deal better” 25. An a priori score of ≥5 
was identified as the cut-off of a successful outcome 25. The validity and reliability of the GROC 
scales has been demonstrated in multiple studies 26,27.   
 
The Kujala score is a 13-item self-reported questionnaire, which quantifies subjects’ 
reported pain levels during a wide variety of activities. The scale highest scores are 100 points, 
which indicate lower disability. It has been shown to be a reliable and valid method for assessing 
functional outcomes in subjects with knee pain 28,29.  
The NPRS is a self-reported questionnaire with adequate reliability and validity 28. Subjects 
were asked to rate their level of pain at baseline from three different reference points: the greatest 
amount of knee pain they had experienced, the least amount of knee pain they had experienced, 
and the level of knee pain that they were currently experiencing. These three values were then 
averaged to create a baseline measure of pain for each subject. All subsequent questionnaires 
corresponded only to subjects’ present level of knee pain.  
Finally, the lateral step down test (LSDT) is a measure of functionality that has been 
demonstrated to be both reliable and valid 30. Subjects were instructed to stand with the test leg on 
a 15-cm step. They were then instructed to lower their body enough to cause the heel of the 
opposite leg to make contact with the floor directly in front of the step, and subsequently return 
the knee to the fully extended position. This represented a single repetition. Subjects completed as 
many repetitions as they could within 15 seconds, and the number of successfully completed 

7 
 
repetitions was recorded. This method has been widely used to ascertain functional performance 
in subjects with knee pain 30,31. 
Statistical Analyses 
A sample size of 50 subjects was estimated using a medium effect size of 0.25, a power of 
0.80 and level of significance set at 0.05. However, we have complete data for 41 participants who 
were randomly assigned to either ProtonicsTM knee brace or sport cord group. 
Data analysis was performed using SPSS Statistics Software version 24.0 (IBM Corp, 
Armonk, NY). Mean + SD was computed for quantitative variables and frequencies (%) for 
categorical variables. Normality of quantitative variables was assessed using Shapiro-Wilk test 
and boxplots. We compared mean age (years), Body Mass Index (kg/m2) (BMI), pain duration, 
and the outcome measures at baseline in both groups at baseline using independent t-test when the 
distribution of the variable was approximately normal and Mann-Whitney test when the 
distribution was not normal. The distribution of qualitative variables (gender, affected leg) by 
group type was examined using Chi Square test. To examine the effect of the type of intervention 
on outcome measures over time (baseline versus immediate versus two weeks versus four weeks), 
a 2x4 mixed factorial ANOVA was conducted while controlling for age at baseline since the mean 
age was significantly different between the two groups. The level of significance was set at p< 
0.05.  
Results 
Subjects’ Demographics 
A total of 43 subjects with mean age of 28.8±5.0 years and body mass index of 25.6±4.7 
kg/m2 participated in the study. One subject was excluded as they had a meniscus lesion that 
prohibited them from participating in the study, and another subject voluntarily left the study due 

8 
 
to personal time constraints, therefore only data from the 41 remaining subjects who completed 
the prescribed intervention was analyzed. Fifty-one percent of the subjects were males (n = 21) 
and the majority had their right knee affected (56.1%, n=23. Twenty-one subjects (51.2%) were in 
the ProtonicsTM brace group and 20 (48.8%) in the sport cord group. There was no significant 
difference between the two groups in mean baseline characteristics and outcome measures at 
baseline except for age (30.8±5.6 vs. 26.7±3.0, p=0.01) and LSDT score (7.0±2.8 vs. 9.1±2.7, 
p=0.02, Table 2).  
Clinical Outcomes 
Clinical improvement of subjects’ patellofemoral movement impairments were assessed 
using four indicators: APT, hip internal/external rotation, and iliotibial band flexibility. Based on 
the results from all four indicators, a significant improvement was seen in all cases for both study 
groups for four weeks (p<0.001, Tables 3&4). APT, hip internal rotation, hip external rotation, 
and iliotibial band flexibility were measured at baseline, immediately following the first session, 
at two weeks, and at four weeks. The degree of APT decreased significantly in brace and sport 
cord groups (59.8% vs. 38.9%, p<0.001; respectively), however those in the brace group had 
sharper and quicker decrease in APT (Table 4). Hip internal rotation also increased significantly 
in both groups over the course of the study (p<0.001, Table 4). Similarly, hip external rotation 
significantly increased for both groups (p<0.001, Table 4). Lastly, iliotibial band flexibility 
increased significantly (p<0.001) for both the brace group and sport cord groups by 87.4% and 
62.5%, respectively, with those in the brace group achieving a lower but non-significant mean 
score (Table 4). 
Functional Outcomes 

9 
 
Function of the knee joint was assessed with the Kujala Score and the lateral step-down 
test. Satisfaction was evaluated with the GROC, and pain was assessed according to the NPRS 
score. The level of satisfaction observed in the brace group was significantly higher than that of 
the sport cord group at the end of the four-week intervention (p<0.01, Table 3). There were no 
significant differences between the two groups with respect to the other three outcomes. The results 
of the Kujala score indicated that there was a significant improvement in knee function for both 
groups (13.7% vs. 10.3%, p<0.001, Table 3). The mean score for the brace group improved by 
74.6%, while those in the sport cord group had 47.4% improvement. All subjects were able to 
perform significantly better on the lateral step test post-intervention ((p<0.001, Table 4). The brace 
group exhibited a 133.3% improvement in their performance, while those in the sport cord group 
demonstrated only an 85.3% improvement. NPRS score decreased significantly for both groups 
after four weeks ((p<0.001, Table 3). 
 
 
 
 
 
 
 

10 
 
Tables 
 
Table 1. Phases of Exercise Intervention 
 
 
 
 
 
 
 
 
 
 
 
 
 
Phase 
Week  
Frequency 
Activities 
Phase I 
1st Day of Week 1 
1 Session 
Education 
Warm-up 
Walking 
Phase II 
Weeks 1-2 
3 Sessions per Week 
Walking 
Hamstring curl in supine, prone, 
and sitting positions 
Phase III 
Weeks 3-4 
3 Sessions per Week 
Walking 
Hamstring curl in standing 
position 

11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Table 2. Mean ± SD of baseline characteristics and outcome measures by study group 
(N=41) 
Variables 
Brace (n1=21) 
Sport Cord (n2=20) 
p-value 
Female, n (%) 
12 (57.1) 
8 (40) 
0.27 
Right Leg,, n (%)  
10 (47.6) 
13 (65) 
0.26 
Age (year) 
30.8±5.6 
26.7±3.0 
0.01 
Height ( cm) 
167.9±10.9 
166.9±9.2 
0.75 
Weight (kg) 
69.3±16.4 
75.1±16.4 
0.26 
BMI (kg/m2) 
24.4 ±4.2 
26.8±4.8 
0.09 
Pain Duration*(days) 
730 (30,4705) 
530 (37,3650) 
0.16 
PNRS 
4.5±1.5 
3.8±0.7 
0.07 
Kujala score 
74.8±15.0 
79.3±8.11 
0.24 
Pelvic Tilt (º) 
5.0±3.0 
3.2±2.6 
0.05 
Lateral Step-Down Test 
7.0±2.8 
9.1±2.7 
0.02 
Hip Internal Rotation 
25.9±6.3 
28.8±7.6 
0.19 
Hip External Rotation 
31.5±5.0 
31.3±4.8 
0.91 
Iliotibial Band 
3.5±3.0 
3.2±2.4 
0.74 
Abbreviation: SD, Standard Deviation; BMI, Body mass index 
*: median (minimum, maximum) 
 

12 
 
 
 
 
 
 
 
Table 3. Mean  SD of pain, global rating of change scale, and Kujala score by study group over time (N=41) 
Variable 
Protonic Brace (n1=21) 
Sport Cord (n2=20) 
Time 
Baseline 
Immediate 
Two 
Weeks 
Four 
Weeks 
Baseline 
Immediate 
Two 
Weeks 
Four 
Weeks 
p-
value 
over 
time 
(η2) 
p-value 
between 
groups 
(η2*) 
NPRS 
4.5± 1.2 
3.0±1.9 
1.9±1.7 
1.1±1.7 
3.8±1.2 
3.2±1.9 
2.5±1.7 
2.0±1.7 
<0.001 
(0.50) 
0.9 
(0.01) 
GROC 
- 
1.0±2.1 
3.0±2.2 
4.6±2.3 
- 
0.0±2.1 
1.3±2.2 
3.0±2.3 
<0.001 
(0.42) 
 
<0.01 
(0.20) 
Kujala 
Score 
74.8±12.1 
- 
84.4±12.8 
87.5±15.1 
79.3±12.1 
- 
84.4±12.8 
87.5±15.1 
<0.001 
(0.38) 
0.39 
(0.02) 
Abbreviations: PNRS, Numeric Pain Rating Scale; GROC, Global Rating of Change Scale; SD, Standard Deviation 
*η2 = effect size  

13 
 
 
Table 4. Comparison of mean  SD of HIR, HER, ITB flexibility, pelvic tilt (°), and LSDT by study group over time (N=41)  
Variable 
Protonic Brace (n1=21) 
Sport Cord (n2=20) 
 
Time 
Baseline 
Immediate 
Two 
Weeks 
Four 
Weeks 
Baseline 
Immediate 
Two 
Weeks 
Four 
Weeks 
p-
value 
over 
time 
(η2) 
p-value 
between 
groups 
(η2) 
Pelvic 
Tilt 
5.0±2.8 
4.4±2.4 
3.1±2.0 
2.0±1.6  
3.2±2.8 
2.5±2.4  
2.5±2.0 
1.9±1.6 
<0.001 
(0.32) 
0.08 (0.1) 
LSDT 
7.0±2.7 
9.6±3.3 
13.3±3.2  
16.3±3.3 
9.1±2.7 
11.8±3.3 
14.7±3.2 
16.8±3.3 
<0.001 
(0.53) 
0.35 
(0.02) 
HIR  
25.9±7.0 
25.5±5.5 
29.2±5.0 
29.4±5.8 
28.8±7.0 
29.3±5.5 
31.6±5.0 
32.6±5.8 
<0.001 
(0.24) 
0.06 (0.1) 
HER 
31.3±4.9 
32.2±5.0 
32.3±5.2 
33.9±5.7 
31.3±4.9 
32.2±5.0 
32.3±5.2 
33.9±5.7 
<0.001 
(0.15) 
0.33 
(0.03) 
ITB 
3.5±2.7 
2.1±2.3 
2.8±1.9 
0.4±2.2 
3.2±2.7 
2.5±2.3 
1.8±1.9 
1.2±2.2 
<0.001 
(0.23) 
0.96 (0.0) 
Abbreviations: HIR, Hip Internal Rotation; HER, Hip External Rotation; ITB, Iliotibial Band; LSDT, Lateral Step-Down Test 
 
 
 
 
 
 
 
 
 
 
 
 
   
 
 
 
 
 
 
 
 
 

14 
 
Figures 
Figure 1. Consort Flow Diagram. 
 
          
 
          
 
          
 
 
 
 
 
 

15 
 
Figure 2. Demonstration of seated hamstring curl with ProtonicsTM knee brace. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

16 
 
Figure 3. Demonstration of prone hamstring curl with sport cord. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

17 
 
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