Keywords knee joint - patellofemoral pain syndrome - braces - athletes
Introduction
Anterior knee pain is currently one of the problems most frequently encountered in
orthopaedic settings and one of the most difficult to manage.[1 ]
[2 ] Retropatellar and peripatellar pain, clinically referred to as patellofemoral pain
(PFP), is a common disorder experienced by young adult and adolescent athletes who
participate in jumping, cutting, and pivoting sports.[3 ]
[4 ]
[5 ] Prevalence of PFP seems to be higher in females.[6 ]
[7 ] This is probably due to anatomical, neuromuscular, and hormonal factors.[8 ]
Patellofemoral disorders may be divided into three groups: objective patellar instability,
potential patellar instability, and PFP.[9 ] Pain is the main symptom of potential patellar instability, which is characterized
by the presence of at least one of the main factors of instability, namely, trochlear
dysplasia, patella alta, and pathological tibial tuberosity-trochlear groove distance.
Pain is also the main symptom of PFP syndrome (PFPS), in which the pain has a mainly
nonpatellar origin (hip, ankle, spine, etc.).[10 ]
[11 ]
In the absence of chondral lesions, conservative treatment is usually the first option
for the PFPS. This approach, based on an appropriate rehabilitation program, is designed
to manage pain and promote recovery of the range of motion (ROM), as well as muscle
strength and proprioception.[12 ] Rehabilitation is often supported by the use of knee braces and foot orthoses.[13 ]
Knee braces have been shown to reduce pain by reducing patellofemoral pressure and
increasing the contact area to allow a better distribution of the forces over the
patellofemoral joint.[2 ]
[12 ]
[14 ]
[15 ] Their effectiveness has been explored in several studies, with contrasting results.[16 ]
[17 ]
[18 ]
[19 ]
[20 ]
[21 ]
[22 ]
[23 ]
[24 ]
The purpose of this study was to assess the efficacy of a new knee brace with elastomeric
properties specifically developed for athletes, in adjunct to a purposed rehabilitation
program, in relieving symptoms in patients affected by PFPS. The hypothesis of the
study was that the knee brace has a significant effect on symptoms relief in patients
affected by PFPS.
Methods
This study was designed as a prospective randomized multicenter study. Seventy patients
were recruited at the Knee Surgery Unit of the G. Pini Orthopaedic Institute in Milan
and at the Orthopaedic Clinic of the University Hospital of Sassari. All the patients
included were informed of the randomized nature of the study, and signed a purposed
informed consent. The institutional review boards approved the study and all the procedures
were in accordance with the current ethical standards.
Inclusion criteria were: age between 16 and 35 years, a diagnosis of anterior knee
pain due to PFPS, a Tegner score of ≥ 3, and a body mass index (BMI) between 18 and
26. Patients with knee comorbidities, such as ligament, meniscus, or cartilage lesions,
were excluded.
Patients were randomized into two groups. In group A, patients underwent a rehabilitation
program combined with the use of a knee brace (Reaction Knee Brace; DJO Global, Vista,
California, United States); in group B, they underwent only rehabilitation. The rehabilitation
protocol was divided into different phases based on the patient's progress. The goal
of the first phase was to reduce pain and swelling, to improve the balance between
vastus medialis and vastus lateralis of the quadriceps muscle, to restore normal gait,
and to decrease loading of the patellofemoral joint. The second phase included improvement
of postural control and coordination of the lower extremity, increase of quadriceps
and hip muscle strength, and restoration of good knee function. The patients were
encouraged to return to sports with a suitable regular physical exercise. The third
phase included functional exercises.
All the patients were assessed before treatment and again at 3, 6, and 12 months afterwards,
using a specifically designed instrument for scoring patellofemoral disorders (Kujala
scale)[25 ] and a pain visual analog scale (VAS). In addition, time to return to sport and subjective
patient satisfaction at the end of treatment were also recorded.
A 2 × 4 univariate analysis of variance (ANOVA) explored the effect of the brace versus
no braced conditions over the different time points using the baseline as a covariate
for the Kujala score and pain VAS. Time effect, group effect, and time per group interaction
were explored by the use of repeated measure ANOVA. Significance was set at p -value of < 0.05.
Results
Following the exclusion of 10 patients who were lost during the study or at follow-up,
data analysis included 60 patients (all nonprofessional athletes) ([Fig. 1 ]). These comprised of 47 females and 13 males, with a mean age of 20 ± 4 years (range,
16–30 years) and a mean BMI of 23 (range, 18–26). The two groups did not show significant
differences for age, gender, and BMI. [Table 1 ] shows the descriptive statistics for group A (knee brace used in combination with
a rehabilitation program) and group B (rehabilitation alone) at the different time
points.
Table 1
Descriptive statistics for group A (knee brace used in combination with a rehabilitation
program) and group B (rehabilitation alone)
Groups
Time interval
Kujala score,
mean (SD)
VAS score,
mean (SD)
Group A
Baseline
74.3 (7.1)
6.0 (1.9)
3 months
77.1 (7.9)
2.9 (1.9)
6 months
79.8 (6.9)
1.4 (1.6)
12 months
80.9 (7.5)
0.9 (1.4)
Group B
Baseline
70.4 (7.2)
5.9 (1.6)
3 months
74.7 (8.1)
3.7 (1.5)
6 months
76.9 (8.6)
3.0 (1.5)
12 months
78.4 (8.3)
1.8 (1.7)
Abbreviations: SD, standard deviation; VAS, visual analog scale.
Fig. 1 Flow diagram of patients throughout the course of the study.
The mean Kujala score showed a constant and progressive improvement over the follow-up
period. The mean score at 6 months was 79.8 ± 6.8 points (range, 66–95) in group A
and 76.8 ± 8.6 points (range, 60–95) in group B, rising at 12 months to 80.9 ± 7.5
points (range, 70–100) in group A and 78.4 ± 8.3 points (range, 67–100) in group B.
Successive reductions were observed in the mean VAS score, which fell from a common
value of 5.9 ± 1.9 points (range, 3–9) in both groups at baseline, to 1.4 ± 1.5 (range,
0–7) in group A and 3 ± 1.6 (range, 0–6) in group B at 6 months, and then to 0.9 ± 1.3
points (range, 0–5) in group A and 1.8 ± 1.6 (range, 0–5) in group B at 12 months
([Fig. 2 ]).
Fig. 2 Line diagrams of outcomes throughout the course of the study.
At 6 months, 42 of the 60 patients returned to sports; 24 of these were from group
A and 14 from group B. Of the patients that used the brace, 75% declared that they
were satisfied or very satisfied with it.
The mean Kujala score showed no significant differences between the two groups but
did show significant differences between time points (p < 0.001). Further post hoc pairwise comparison testing showed significant differences
between all time points showing continuous improvement in both groups up to 12 months
([Table 2 ]).
Table 2
Pairwise comparisons of time points for Kujala scores
Group A + B
Mean differences
p -Value
95% CI of difference
Baseline vs. 3 mo
–3.25
< 0.001
–4.72
–1.78
Baseline vs. 6 mo
–5.75
< 0.001
–7.22
–4.28
Baseline vs. 12 mo
–7.32
< 0.001
–8.75
–5.89
3 vs. 6 mo
–2.50
0.001
–4.01
–0.99
3 vs. 12 mo
–4.07
< 0.001
–5.54
–2.60
6 vs. 12 mo
–1.57
0.036
–3.04
–0.10
Abbreviation: CI, confidence interval.
Significantly lower mean pain VAS was seen in group A (p < 0.001) and between time points (p < 0.001). In addition, a significant interaction between the two factors was also
seen (p < 0.001), and the repeated measures ANOVA performed separately on the two groups
showed significant differences between all time points for both groups ([Table 3 ]).
Table 3
Pairwise comparisons of time points for VAS scores
Group A
Mean differences
p -Value
95% CI of difference
Baseline vs. 3 mo
3.30
< 0.001
2.81
3.80
Baseline vs. 6 mo
4.61
< 0.001
4.01
5.20
Baseline vs. 12 mo
5.30
< 0.001
4.49
6.12
3 vs. 6 mo
1.30
0.001
0.63
1.97
3 vs. 12 mo
2.00
< 0.001
1.19
2.81
6 vs. 12 mo
0.70
0.006
0.22
1.17
Group B
Baseline vs. 3 mo
2.16
< 0.001
1.79
2.53
Baseline vs. 6 mo
2.84
< 0.001
2.49
3.19
Baseline vs. 12 mo
4.20
< 0.001
3.80
4.60
3 vs. 6 mo
0.68
0.001
0.31
1.05
3 vs. 12 mo
2.04
< 0.001
1.62
2.46
6 vs. 12 mo
1.36
< 0.001
0.92
1.80
Abbreviations: CI, confidence interval; VAS, visual analog scale.
Discussion
The best therapeutic approach to anterior knee pain is conservative treatment consisting
of the use of nonsteroidal anti-inflammatory drugs for short periods of time, together
with targeted rehabilitation programs and the application of forces to restore medial
alignment of the patella.[11 ] The latter objective is mainly achieved through the use of taping and knee braces.[12 ] The precise mechanism by which either of these solutions may be effective is not
entirely known. The knee braces traditionally available on the market are mostly designed
and constructed to apply an external, medially directed force that, in theory, counteracts
the “maltracking” that tends to result in lateralization of the patella. Published
literature on the use of such braces is conflicting.[23 ] Draper et al,[19 ] in an magnetic resonance imaging study on females with PFP, demonstrated that a
brace applying a medial load to the patella can reduce lateral translation of the
patella and lateral tilt more effectively than a functional bandage can. Powers at
al[13 ] found improvement of pain and better activation of the quadriceps during ascending
and descending stairs when using bracing. Further effects on knee joint biomechanics
were studied by Selfe et al,[22 ]
[26 ] who demonstrated improved coronal plane and torsional control of the knee during
eccentric quadriceps contractions in subjects with soft knee braces. Thijs et al[24 ] and Callaghan et al[16 ] reported proprioceptive effects and increased motor neuron activity; the latter
detected modulation of the supplementary motor area, the cingulate motor area, and
other neural areas of the brain during a proprioception knee motor task performed
with and without bracing and patellar taping, respectively. In addition, D'Hondt et
al[18 ] and Crossley et al[17 ] performed meta-analyses that highlighted better outcomes in patients using knee
braces, namely, reduced pain, improved function, and a lower patellofemoral congruence
angle. However, these papers also underlined the poor quality of studies in this setting,
also drawing attention to publications with limited level of evidence.[27 ] Conflicting results may also be attributable to variations in orthosis/brace designs
used.
The knee brace used in this study implements an active approach that, in addition
to controlling the vertical movement of the patella, ensures return of the kinetic
energy accumulated during the specific sport-related flexion movement, thus lessening
its impact forces. The brace features an anterior web-like structure made up of elastomeric
bands that act like an elastic exoskeleton and, through elongation of the extensible
components, attenuate the forces of impact on the joint, thus ensuring maintenance
of proprioceptive contact throughout the entire ROM. The effect of web-like structure
has been shown to improve knee stability during different sport-related motor tasks
in healthy subjects, which has implications to the management of individuals with
knee instability.[20 ]
[28 ] Furthermore, during sports activities, the web-like structure claims to distribute
the forces exerted more evenly on the patellofemoral joint and extensor mechanism.
The results of our study seem to indicate that this brace may be a useful aid in the
treatment of anterior knee pain in amateur athletes, speeding up their return to sport
and allowing better pain management.
Our results showed that the most significant improvement concerned pain, which was
reduced by mean of over 5 VAS points, with a significant difference (p < 0.05) between the two groups in favor of the group who received knee bracing. We
observed a progressive and significant improvement of all scores across all the time
points in both the groups on VAS and Kujala scales. Moreover, 24 out of 30 patients
in the group who received knee bracing returned to sport at 6 months, as opposed to
only 14 of those who received the rehabilitation program only. This demonstrated that
the rehabilitation program appears to be more effective when combined with the use
of brace. Furthermore, 75% of the patients with brace were satisfied with the treatment,
thus confirming the good level of compliance with the use of brace.
Our study has several limitations. No comparison was made with other types of brace;
the sample of patients studied was small and they practiced different types of sport.
All of these factors could potentially have biased our results.
In conclusion, the results of this study showed that the Reaction Knee Brace may be
an effective adjunct to reducing pain in individuals with anterior knee pain and for
speeding up their return to sport. As with taping,[29 ] the mechanisms by which these benefits are obtained remain unclear; they could be
linked to a redistribution of stress forces, increased proprioceptive inputs, and
increased neuromuscular control, which may be facilitated by the web-like structure
of the knee brace and then may produce better quadriceps activation and greater control
over the execution of sports exercises. Further biomechanical and clinical studies
are needed to investigate more in-depth the mechanisms underlying the effectiveness
of such devices and their role in rehabilitation.
