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Isometric Contraction of the Quadriceps Improves
the Accuracy of Intra-Articular Injections into the
Knee Joint via the Superolateral Approach
Makoto Wada, MD, Tadashi Fujii, MD, PhD, Yusuke Inagaki, MD, PhD, Tatsuo Nagano, MD, and Yasuhito Tanaka, MD, PhD
Investigation performed at the Department of Orthopaedic Surgery, Wada Orthopaedic Clinic, Hirakata, Japan, and the Department of Orthopaedic
Surgery, Kashiba Asahigaoka Hospital, Kashiba, Japan
Background: Intra-articular injection is an important technique for treating rheumatoid arthritis and osteoarthritis of
the knee. However, medication is often inaccurately injected outside of the joint. We devised an intra-articular
injection method in which the needle is inserted into the suprapatellar bursa while the patient maintains isometric
contraction of the quadriceps. This isometric contraction method is based on the concept that isometric contraction
of the quadriceps induces contraction of the articularis genus muscle, thus expanding the lumen of the suprapatellar
bursa.
Methods: Intra-articular injections were performed on 150 osteoarthritic knees without effusion. The knees were
alternately assigned to the isometric quadriceps method group (75 knees) and non-activated quadriceps method group
(75 knees). Prior to joint injection, the anterior-posterior dimension of each suprapatellar bursa was measured to
ascertain its expansion. The isometric quadriceps method was performed with the quadriceps and the articularis genus
muscle maintained in a contracted state. The non-activated quadriceps method was performed in a relaxed state.
Ultrasound guidance was not used for either method. Subsequently, an ultrasonic probe was used only to confirm
whether the intra-articular injections were successful. We compared the accuracy of injections performed between the 2
groups.
Results: Suprapatellar expansion was significantly larger (p < 0.001) using the isometric quadriceps method (2.1 ±
1.4 mm [range, 0 to 5 mm]) than using the non-activated quadriceps method (0.8 ±0.7 mm [range, 0 to 2 mm]). The
percentage of accurate intra-articular injections was significantly higher (p =0.0287) using the isometric quadriceps
method (93%) compared with the non-activated quadriceps method (80%).
Conclusions: In comparison with the non-activated quadriceps method, the isometric quadriceps method led to a
larger expansion of the suprapatellar bursa, which should lead to more accurate intra-articular injections. The
isometric quadriceps method is effective in reducing inaccurate injections into the synovium or surrounding fatty
tissues.
Clinical Relevance: Putting force on the quadriceps muscle increases the success rate of intra-articular injection of the
knee. The results of this study could provide a clinically relevant injection technique for future treatment.
The treatment of knee osteoarthritis and rheumatoid
arthritis can involve intra-articular injections of corti-
costeroids, hyaluronic acid, or other drugs. However, it
has been reported that, in some cases, medication is mistakenly
injected into the surrounding synovium, suprapatellar fat pad,
or prefemoral fat pad
1-3
. Patients receiving inaccurate injections
can report extreme pain. In such cases, it is possible that the
injection was not into the suprapatellar bursa but rather into the
synovial tissue, which has many nerve endings
4,5
.
The risk of extra-articular injections rises in patients with
an abundance of subcutaneous fat and little effusion
6
, which
makes it difficult for physicians to sense whether the needle has
penetrated the suprapatellar bursa. To prevent pain associated
with extra-articular injections
7
and to ensure that an injected
Disclosure: There was no source of external funding for this study. The Disclosure of Potential Conflicts of Interest forms are provided with the online
version of the article (http://links.lww.com/JBJSOA/A73).
Copyright Ó2018 The Authors. Published by The Journal of Bone and Joint Surgery, Incorporated. All rights reserved. This is an open-access article distributed under the terms of
the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited.
The work cannot be changed in any way or used commercially without permission from the journal.
JBJS Open Access d2018:e0003. http://dx.doi.org/10.2106/JBJS.OA.18.00003 openaccess.jbjs.org 1
drug is effective, a reliable method to inject into the joint should
be established. Ultrasound guidance is considered to be the best
method to ensure that the needle tip is placed accurately
8-12
.
However, ultrasound equipment is not available in many med-
ical facilities. Thus, an accurate method for administering blind
intra-articular injections (injections without ultrasound guid-
ance) would be desirable. A literature search of previous studies
indicated that various approaches have been attempted
13-19
.
Many of these involve changing the position of the knee and
anatomical landmarks
8,9
.
We believe that using the isometric quadriceps contrac-
tion method, which focuses on the expansion of the suprapa-
tellar bursa by inducing isometric contraction of the quadriceps
and the articularis genus muscle (Video 1), would enable greater
accuracy in delivering intra-articular injections to patients with
arthritis without effusion.
In this study, we compared the expansion of the supra-
patellar bursa and the accuracy rate of intra-articular injections
between the isometric quadriceps contraction method and the
non-activated quadriceps method.
Materials and Methods
One hundred and fifty knees that underwent intra-articular
injection for the initial treatment of knee osteoarthri-
tis without effusion in our outpatient department between
December 2016 and June 2017 were enrolled. Knees with
osteoarthritis severity rated as Kellgren and Lawrence grades
I to III were included. Subjects with a knee mobility range
that restricted extension by ‡10°were excluded. Sonographic
examination was performed to check synovial fluid retention.
Patients with a >2-mm anterior-posterior dimension of the
suprapatellar bursa when in the supine position with the
knees naturally extended were excluded. After exclusion,
the 150 knees were alternately assigned to the isometric
quadriceps contraction group or the non-activated quadriceps
group as a controlled clinical trial using quasi-randomization
(Fig. 1).
Wedeterminedthesamplesizeasfollows.Basedon
previous studies
14-19
, sample size was calculated assuming
that the treatment success rate of the isometric quadriceps
contraction method was 95%, and that of the non-activated
quadriceps method was 75% (because of the difficult con-
ditions, the anterior-posterior dimension was £2mm);the
detection power was 90%; and the significancewassetatan
equal 2-sided level of p < 0.05. As a result, the required
number of cases was 75 per group, and the target number of
cases was a total of 150 in both groups.
The isometric quadriceps contraction method was per-
formed on 75 knees in 17 male patients and 58 female patients
with a mean age (and standard deviation) of 72.7 ±8.3 years.
The non-activated quadriceps method was performed on 75
knees in 14 male patients and 61 female patients with a mean
age of 74.4 ±6.6 years. Prior to the study, we obtained the
approval of the institutional review board. Subjects were provided
Fig. 1
Eligibility criteria and flowchart. K-L =Kellgren and Lawrence, NAQ =non-
activated quadriceps, and IQC =isometric quadriceps contraction.
Fig. 2
Fig. 2-A The non-activated quadriceps (NAQ) method. Subjects lie down in the supine position and relax the muscles surrounding the knees. Fig. 2-B The
isometric quadriceps contraction (IQC) method. Subjects lie down with the knees at an angle of approximately 25°on a pillow. Subsequently, the knees are
kept fully extended by firmly contracting the quadriceps muscle.
Isometric Contraction of the Quadriceps Improves the Accuracy of Intra-Articular Injections
JBJS Open Access d2018:e0003. openaccess.jbjs.org 2
an explanation of the purpose of the study and methods, and
their consent was received.
The ultrasound equipment used was a HI VISION Avius
with an EUP-L75 linear probe (5.0 to 8.0 MHz) (Hitachi).
Ultrasound Observation of the Suprapatellar Bursa and
Anterior-Posterior Dimension Measurements
All patients in both groups (150 knees) were told to relax the
muscles surrounding the knees, the injection condition used in
the non-activated quadriceps method (Fig. 2-A). The anterior-
posterior dimension of the suprapatellar bursa on the longi-
tudinal axis along the midline of the quadriceps tendon was
measured by the same orthopaedic surgeon. The measurement
site was the point proximal to the suprapatellar fat pad, which is
the area with the smallest amount of soft tissue between the
suprapatellar bursa and the quadriceps (Fig. 3-A).
Next, the patients were instructed to place the knees at an
angle of approximately 25°on a pillow and were then in-
structed to extend the knees, as follows: “Please extend your
knee firmly and keep your heel off the bed.”Subsequently, we
touched the quadriceps and said, “Please contract this muscle
firmly.”There were no subjects who could not follow these
instructions. This is the position used in the isometric quad-
riceps contraction method (Fig. 2-B). After manually con-
firming that the quadriceps muscle was in a state of isometric
contraction with the knee extended and the heel off the surface
of the bed, the anterior-posterior dimension was measured
again (Fig. 3-B). The 2 anterior-posterior dimensions were
then compared.
We also validated the reliability of ultrasonographic
measurements of the anterior-posterior dimensions. To as-
sess the intraobserver reliability, the surgeon of this study
measured 6 healthy knees on 3 days at 1-week intervals.
Threemeasurementsweredoneoneachday,andthemean
values on the 3 days were compared. For interobserver re-
liability, 4 examiners measured 4 healthy knees each, 3 times
per knee. The measurement order was randomly assigned.
Reliability was assessed by calculating intraclass correlation
coefficients.
Statistical analysis was performed using SAS 9.4 (SAS
Institute). Significant differences were determined using the
Mann-Whitney U test (p < 0.05).
Fig. 3
Ultrasonography assessments of the suprapatellar bursa (SPB) expansion on the non-activated quadriceps (NAQ) method (Fig. 3-A) and the isometric
quadriceps contraction (IQC) method (Fig. 3-B). The anterior-posterior dimension of the SPB (bar marked by arrow) was measured vertically to the femoral
bone. The target point for the needle to successfully enter the SPB is this measurement point immediately proximal to the suprapatellar fat pad (SPF). The
SPB expands maximally in the anterior-posterior plane at this point, which is an area with relatively little obstruction.
TABLE I Differences Between the 2 Groups
Isometric
Quadriceps
Contraction
Group (N = 75)
Non-Activated
Quadriceps
Group (N = 75) P Value
Sex* 0.687
Male 17 (22.7%) 14 (18.7%)
Female 58 (77.3%) 61 (81.3%)
Age†(yr) 72.7 ±8.3 74.4 ±6.6 0.174
Side* 0.512
Left 32 (42.7%) 37 (49.3%)
Right 43 (57.3%) 38 (50.7%)
*The values are given as the number of patients, with the per-
centage in parentheses. The p value was determined with use of
the chi-square test. †The values are given as the mean and the
standard deviation. The mean difference in years, with the 95%
confidence interval, is 21.25 (23.53 to 1.02). The p value was
determined with use of the t test.
Isometric Contraction of the Quadriceps Improves the Accuracy of Intra-Articular Injections
JBJS Open Access d2018:e0003. openaccess.jbjs.org 3
Intra-Articular Injection Method and Accuracy Measurement
The skin was pierced at a point on the lateral side of the
quadriceps tendon approximately 1 cm proximal to the supe-
rior margin of the patella. The needle tip was angled toward the
suprapatellar bursa without ultrasound guidance. It was stop-
pedwhenthesurgeonsensedthattheneedlehadpierced
the synovial membrane of the suprapatellar bursa (Video 1).
The target point for the needle was the measurement site of the
anterior-posterior dimension, which is an area with relatively
little obstruction (Fig. 3). Once the drug solution was injected,
an ultrasound probe was used parallel to the needle to capture
its image and confirm whether the solution diffused within the
joint. A 25-G needle and 1% hyaluronic acid (low molecular
weight, approximately 900 kDa) solution at a dose of 2.5 mL/
injection (Artz [purified sodium hyaluronate]; Seikagaku) were
employed.
We performed this procedure for both the non-activated
quadriceps method and the isometric quadriceps contrac-
tion method. Prior to extending the knee, the skin puncture
point was confirmed, because it becomes difficult to pal-
pate the margin of the patella because of isometric con-
traction of the quadriceps. The percentages of accurate
intra-articular injections within the 2 groups were compared.
Statistical analysis was performed with the Fisher exact test
using SAS 9.4.
Results
There were no significant differences (p < 0.05) with regard
to sex, age, or side between the isometric quadriceps
contraction group and the non-activated quadriceps group
(Table I). We found that the anterior-posterior dimension in
the isometric quadriceps contraction method was significantly
greater (p < 0.001) than that in the non-activated quadriceps
method (Table II). Also, the success probability of the isometric
quadriceps contraction method was higher than that of the
non-activated quadriceps method (Table III).
When performing the isometric contraction method, the
intraclass correlation coefficients of the sonographic measure-
ments were 0.999 for intraobserver reliability and 0.935 for
interobserver reliability (Tables IVand V). High reliability was thus
obtained for both intraobserver and interobserver correlations.
Discussion
The results of this study indicate that the suprapatellar bursa
is likely to expand during isometric quadriceps contrac-
tion, improving the probability of successful intra-articular
injections.
We believe that the isometric quadriceps contraction
method is therapeutically effective and could reduce the risk of
injection pain due to inaccurate injections into the synovial
membrane, which has a large number of nerve endings
4,6,7
.
TABLE II Expansion of the Suprapatellar Bursa According to
Injection Technique
Method
Anterior-Posterior
Dimension* †
Isometric quadriceps contraction 2.1 ±1.4 (2.0 [0 to 5])
Non-activated quadriceps 0.8 ±0.7 (1.0 [0 to 2])
*The values are given as the mean and the standard deviation, in
millimeters, with the median in parentheses and the range in
brackets. †Significantly different at p < 0.001, determined with use
of the Mann-Whitney U test.
TABLE III Comparison of Intra-Articular Injection Accuracies*
Method
Total
No.
No. with
Success
Success
Rate
Isometric quadriceps
contraction
75 70 93.3%
Non-activated quadriceps 75 60 80%
*The p value between the 2 groups, determined with use of the
Fisher test, was p = 0.0287.
TABLE IV Intraobserver Reliability of Ultrasonographic
Measurement of the Anterior-Posterior Dimension
of the Suprapatellar Pouch*
Subject No. First Day†Second Day†Third Day†
1 3.73 3.70 3.86
2 3.60 3.63 3.63
3 1.93 2.07 2.00
4 1.60 1.70 1.63
5 2.53 2.70 2.67
6 4.60 4.47 4.60
*The intraclass correlation coefficient was 0.999 (95% confidence
interval, 0.995 to 1.000). †The value is given as the mean value of
3 measurements, in millimeters.
TABLE V Interobserver Reliability of Ultrasonographic
Measurement of the Anterior-Posterior Dimension
of the Suprapatellar Pouch*
Subject
No.
Observer
1†
Observer
2†
Observer
3†
Observer
4†
1 3.68 3.83 3.78 3.78
2 3.50 3.25 3.60 3.53
3 4.85 4.35 4.23 4.70
4 3.20 3.95 3.75 3.83
*The intraclass correlation coefficient was 0.935 (95% confidence
interval, 0.711 to 0.995). †The value is given as the mean value of
3 measurements, in millimeters.
Isometric Contraction of the Quadriceps Improves the Accuracy of Intra-Articular Injections
JBJS Open Access d2018:e0003. openaccess.jbjs.org 4
There are many reports providing evidence for the
validity of ultrasound in detecting structural pathology
20-22
, and
good agreement between ultrasonography and magnetic reso-
nance imaging (MRI) in visualizing effusion and synovial hyper-
trophy with knee osteoarthritis has been shown
23
. The reliability in
this current study, as shown by intraclass correlation coefficients,
was also very high. Thus, ultrasound measurement is effective for
evaluating the expansion of the suprapatellar bursa, which occurs
as discussed below.
The quadriceps tendon becomes tense under isometric
contraction; therefore, the space between the tendon and the
femoral bone increases. The articularis genus muscle syn-
chronously contracts with the quadriceps and lifts the supra-
patellar bursa to a proximal position, preventing it from being
entrapped in the patellofemoral joint
24-28
. Thus, the suprapa-
tellar bursa can expand in this space under the quadriceps
tendon. In addition, when subjects contract the quadriceps
muscle, the patella is lifted to the proximal position. Tension on
the patellar tendon and the patellar retinaculum moves the Hoffa
fat pad toward the femoral condyles and intercondylar space,
reducing the lumen of the tibiofemoral joint and patellofe-
moral joint. This moves the joint fluid to the suprapatellar
bursa
20,28
.
Next we will look into difficult cases, such as obese pa-
tients. A large amount of subcutaneous fat makes it difficult to
predict the distance that the needle must travel to reach the
suprapatellar bursa. In such cases, accidental injection into the
wrong tissues, such as the quadriceps tendon, suprapatellar fat
pad, and prefemoral fat pad, may occur. There is also a risk of
extra-articular injections when it is difficult for the physician to
detect when the needle has pierced the suprapatellar bursa
synovium.
The expansion of the suprapatellar bursa enables accurate
injections even for individuals with a large amount of subcuta-
neous fat. The articularis genus muscle pulls the suprapatellar
bursa up, which puts the synovium under tension
25-29
and
therefore makes it easier to determine when the needle tip has
pierced it. As a result, the probability of successfully adminis-
tering an intra-articular injection increases, and, conversely,
the risk of administering an inaccurate injection is reduced.
When synovial fluid is present under the vastus lateralis
and vastus medialis muscles
30
, movement of the fluid can be
detected by palpation. Clinically, when patients have a large
amount of synovial fluid, fluid can be aspirated without any
special treatment. However, for patients with only a small
amount of synovial fluid, the fluid was manually gathered into
the suprapatellar bursa prior to performing aspirations.
This accumulation is difficult in cases in which the anterior-
posterior dimension of the suprapatellar bursa is £2mm.For
subjects with little synovial fluid, isometric contraction of the
quadriceps proved effective for concentrating the synovial fluid
of the tibiofemoral joint and the patellofemoral joint into the
suprapatellar bursa (Fig. 4).
On the basis of this mechanism, we believe that the
isometric quadriceps contraction method can be utilized to
reduce the risk of accidental injection into the fat pads
Fig. 4
The isometric contraction of the quadriceps was effective for concentrating the synovial fluid of the tibiofemoral joint and patellofemoral joint into the
suprapatellar bursa (arrowhead). QT =quadriceps tendon, P =patella, VM =vastus medialis, and VL =vastus lateralis.
Isometric Contraction of the Quadriceps Improves the Accuracy of Intra-Articular Injections
JBJS Open Access d2018:e0003. openaccess.jbjs.org 5
surrounding the suprapatellar bursa and into the quadriceps
tendon.
Maricar et al. gathered data from 23 previous studies with
regard to the accuracy of intra-articular injections administered
via various approaches
14
. According to their systematic review,
the superolateral patellar approach without ultrasonography
had a higher success rate (87%) than the medial midpatellar
approach (64%) and the anterolateral joint line approach
(70%). In their systematic review, Hermans et al. reported that
the superolateral patellar approach resulted in the highest
pooled accuracy of 91%
15
. These systematic reviews included
patients in whom a substantial amount of synovial fluid was
present. In our current study, the superolateral patellar ap-
proach was performed only for subjects with a suprapatellar
bursa anterior-posterior dimension of £2 mm (minimal syn-
ovial fluid accumulation), which means that conditions were
more difficult. Nevertheless, the results indicated that isometric
contraction of the quadriceps led to a high success rate of
93.3%.
Lockman reported that confirmation by palpation was
difficult for obese patients and other patients with a thick
layer of subcutaneous fat; as a result, he developed an ap-
proach that used the apex of the patella and the femur as
anatomical landmarks
6
. However, we could not find any
previous studies of methods in which patients were directed to
consciously contract the quadriceps and articularis genus
muscles. The isometric quadriceps contraction method in
the present study is a type of superolateral patellar approach,
which was reported by Maricar et al. to have the highest success
rate.
Park et al. reported that the success rate of intra-articular
injections using the superolateral patellar approach was 83.7%
without ultrasound guidance and 96.0% with ultrasound guid-
ance
11
. The accuracy of the isometric quadriceps contraction
method is near that of the ultrasound guidance method.
Ultrasound equipment is not always available. As a
result, many physicians perform intra-articular injections
withoutultrasonography.Whenphysiciansrelyonlyonthe
sense of touch, there are many subjects for whom it is difficult
to ascertain whether the needle has entered the suprapatellar
bursa. The use of the isometric quadriceps contraction tech-
nique allows for more accurate and successful intra-articular
injections even for these subjects without using sonography.
Onelimitationofthisstudywasthatitwasnotanideal
randomized controlled trial; because of the quasi-randomization,
randomness was not guaranteed. However, the background factors
showed no bias between the 2 groups (Table I), and double-
blinding was not applicable in this study because we compared the
methods of injection. In light of the methodology and relatively
small sample size of this current study, further studies with ran-
domization and a larger sample size are needed.
In conclusion, the isometric quadriceps contraction
method can expand the suprapatellar bursa and improve the
accuracy of intra-articular injections. We believe that this
method is a highly useful injection technique for knees with
osteoarthritis without effusion. n
Makoto Wada, MD
1
Tadashi Fujii, MD, PhD
2
Yusuke Inagaki, MD, PhD
3
Tatsuo Nagano, MD
4
Yasuhito Tanaka, MD, PhD
3
1
Department of Orthopaedic Surgery, Wada Orthopaedic Clinic, Hirakata,
Japan
2
Department of Orthopaedic Surgery, Kashiba Asahigaoka Hospital,
Kashiba, Japan
3
Department of Orthopaedic Surgery, Nara Medical University, Kashihara,
Japan
4
Department of Orthopaedic Surgery, Nagano Orthopaedic Clinic,
Kashiba, Japan
E-mail address for M. Wada: m-wada@wadaseikei.com
ORCID iD for M. Wada: 0000-0002-3329-4135
ORCID iD for T. Fujii: 0000-0003-4743-2006
ORCID iD for Y. Inagaki: 0000-0002-1879-4561
ORCID iD for T. Nagano: 0000-0002-2788-0269
ORCID iD for Y. Tanaka: 0000-0002-2300-611X
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Isometric Contraction of the Quadriceps Improves the Accuracy of Intra-Articular Injections
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