Surgical treatment of popliteal cyst: a systematic review and meta-analysis
Zhou et al. Journal of Orthopaedic Surgery and Research
Surgical treatment of popliteal cyst: a systematic review and meta-analysis
Xiao-nan Zhou 0
Bin Li 0
Jia-shi Wang 0
Lun-hao Bai 0
0 Department of Orthopaedics, Shengjing Hospital, China Medical University , 36 Sanhao Street, Heping District, Shenyang, Liaoning 110004 , People's Republic of China
Background: This systematic review and meta-analysis of the clinical efficacy of different surgical methods in the therapy of popliteal cysts may provide evidence about effective surgical treatments. Methods: PubMed, EMBASE, and OVID were searched with the following terms: (popliteal cyst* OR baker's cyst*) AND (arthroscopic OR excision OR operative OR treat* OR surgery). Inclusion criteria included the following: studies reported the efficacy of different surgical methods in popliteal cyst patients; patients were ≥16 years; and studies must have involved a minimum of 10 patients. Studies were grouped according to the surgical methods, and a meta-analysis was employed to identify the success rate based on the pooled data. Results: A total of 11 studies were included: The communication between the cyst and the articular cavity was enlarged in 7 studies; this communication was closed in 3 studies; and only intra-articular lesions were managed in 1 study. After the data were pooled, the success rates were 96.7 and 84.6 % in the communication-enlargement group and communication-closure group, respectively. Studies with communication enlargement were subgrouped into the cyst wall resection group and the non-cyst wall resection group, for which the success rates were 98.2 and 94.7 %, respectively. Conclusions: Based on the current available evidence, at present, any how arthroscopic excision of the cyst wall, arthroscopic management of intra-articular lesions, and enlarging the communication between the cyst and the articular cavity is an ideal strategy for the popliteal cyst. The current literature on the treatment of popliteal cysts is limited to retrospective case series. Future prospective studies with high-quality methodology and uniform scoring system are required to directly compare communication-enlargement surgery and communication-closure surgery and determine the optimal treatment of popliteal cysts. Cyst wall resection may improve the therapeutic efficacy, to draw definitive conclusions, and high-level clinical researches with a large number of patients and long-term follow-up should be initiated.
Popliteal cysts; Surgical intervention; Systematic review; Clinical outcome
Popliteal cysts are a common disease in orthopedics and
the most prevalent cystic lesions around the knee joint
]. They were first recognized by Adama in 1840, and
Baker described them in detail in 1877. Accordingly,
popliteal cysts are also known as Baker’s cysts [
Popliteal cysts most commonly form by distention of the
gastrocnemio-semimembranosus bursa, which is located in
the medial aspect of the popliteal fossa. The
gastrocnemiosemimembranosus bursa is situated between the tendons of
the gastrocnemius and semimembranosus muscles and is a
normal anatomic finding . A series of studies on the
pathogenesis of popliteal cysts revealed the valve structure
bridging the cyst and the articular cavity [
]. In adults,
popliteal cysts usually occur concomitantly with
intraarticular disease, resulting in persistent and excess
production of synovial fluid [
]. Sansone et al. found that 94 %
of popliteal cysts were associated with a disorder of the
knee. The most common disorder was meniscal lesions,
followed by anterior cruciate ligament tear and/or chondral
lesions. Of the meniscal lesions, 70.2 % were medial
meniscal tears, often involving the posterior horn of the medial
]. Moreover, the valve structure leads to a
oneway flow of the synovial fluid, which finally causes synovial
fluid accumulation and subsequent cyst formation.
Although asymptomatic popliteal cysts incidentally detected
do not require treatment, large cysts may cause popliteal
pain or disturbance in the knee range of motion, and they
can be the targets of surgical intervention.
Direct excision of the cyst is associated with high rates of
]. In 1979, Rauschning and Lindgren
reported that the postoperative recurrence rate was as high
as 63 % in 40 patients who received open cyst resection via
the posterior approach . Several studies have reported
frequently associated intra-articular pathologies with the
cysts and warned of a high recurrence rate if the
intraarticular pathologic condition is not addressed [
10, 12, 13
Lindgren reported on the valvular mechanism of the
capsular fold on the posteromedial capsule and
continuous unidirectional flow between the posterior
joint capsule and gastrocnemius-semimembranosus
]. If the valvular mechanism or such a
communication is not corrected during surgery, the
continuous flow of joint fluid will occur, which will
lead to a postoperative recurrence. Therefore, surgical
treatment includes the following aspects: correction of
the intra-articular lesions, closure or enlargement of
the communication between the cyst and the articular
cavity, and resection of the cyst wall. Arthroscopic
correction of the intra-articular disorders aiming at
minimizing the risk of recurrent effusions is crucial
to prevent relapsing of the cyst. Rupp et al. have
completed a study on arthroscopic treatment for
intra-articular lesions without any intervention to the
]. In 5 of the 16 patients, the popliteal cysts
had disappeared; 11 cysts had persisted. Some studies
reported to close the communication between the
cyst and the articular cavity to block synovial fluid
flow into the bursae synovialis [
arthroscopic treatment of popliteal cysts by enlarging
the communication to abolish the one-way flow has
been reported with excellent results in several studies
12, 13, 18–20
]. In addition, studies indicated that
concomitant resection of the cyst wall which may
reduce recurrence rates have yielded very good
therapeutic outcomes [
Although some methods can be used for the surgical
treatment of popliteal cysts, none has been confirmed as
the best. In this meta-analysis, the authors searched
published reports of the outcomes of various surgical
interventions for treatment of popliteal cysts and
compared the success rates between
communicationclosure surgery and communication-enlargement
surgery. Moreover, on the basis of the heterogeneity of
available studies, the influence of cyst wall resection on
the success rate was further evaluated. In this study, we
sought to determine the effectiveness of currently
utilized surgical treatment strategies.
PubMed (1980–July 2015), EMBASE (1980–July 2015),
and OVID (1980–July 2015) were searched on 10 July
2015, using the following terms: (popliteal cyst* OR
baker’s cyst*) AND (arthroscopic OR excision OR
operative OR treat* OR surgery). Inclusion criteria for
studies included the following: The popliteal cyst was
treated by surgery; postoperative therapeutic efficacy
was reported; ≥10 patients in each study; and patients
recruited were ≥16 years old. Exclusion criteria included
the following: non-English-language articles, reviews, and
case reports. All patients had popliteal cyst, and other
identical intra-articular diseases were also excluded (such
as all patients with rheumatoid cysts of the knee [
Two investigators independently examined the titles of
the collected articles and then reviewed the abstract and
full text for inclusion in the study. Any discrepancy was
resolved by discussion or consultation with the third
investigator. In addition, the references of collected articles
were also reviewed and could be included if they met
the inclusion criteria.
The Newcastle–Ottawa scale (NOS) is a simple scale that
is easy to use to evaluate the quality of nonrandomized,
controlled studies (e.g., case–control studies and cohort
]. In the NOS, the stars awarded for each
quality item served as a quick visual assessment based on the
following criteria: the selection of study groups (maximum
4 stars); the comparability of study groups (maximum 2
stars); and the ascertainment of either the exposure or
outcome of interest for case–control or cohort studies,
respectively (maximum, 3 stars). Thus, the maximum
number of stars available for each quality measure was 4, 2,
and 3, respectively, and the highest-quality studies could
be awarded up to 9 stars. The majority of available studies
in orthopedics were case series. Thus, a modified NOS
was employed to evaluate the quality of the case series
included in our analysis. The original modified NOS was
reported by Zengerink et al. to evaluate the quality of case
series, and to date, the modified version has been used in
systemic reviews [
]. The modified NOS is based on
the study design, selection, and outcome, for which the
maximum number of stars was 2, 1, and 2, respectively;
thus, the highest-quality studies were awarded 5 stars
Data extraction and statistical analysis
Data extraction was performed independently by two
investigators. The number of patients included in each study,
mean age, sex, mean duration of follow-up, functional
score, and success rate were recorded. Any discrepancy was
resolved by discussion or by consultation with the third
The Rauschning and Lindgren (RL) knee score was
used to evaluate the outcome and therapeutic efficacy
]. For the RL clinical score, grade 0 or grade 1 at the
last follow-up was employed to define successful
therapy. Other clinical scoring tools have not been widely
used in clinical practice, but there are similarities
between them and the RL clinical score. In the visual
analog scale, a score of 1 to 4 was used to define successful
]. Hughston et al. defined successful therapy
as excellent or good according to patients’ objective and
subjective statuses [
]. In Rauschning’s study, the
clinical scoring tool was similar to the RL scoring tool,
and successful therapy was defined as grade 0 or grade
1. According to these criteria, we could calculate the
success rate in each study.
Metaprop of R 3.2.1 was employed for the
metaanalysis of success rates [
]. A forest plot was used
for heterogeneity evaluation, which was determined
according to p value and I2 value. A value of p > 0.1 or
I2 < 50 % suggested nonevident heterogeneity and a
fixed-effects model. On the contrary, if evident
heterogeneity was present, a random-effects model was used
and the cause of heterogeneity was further explored.
Finally, on the basis of heterogeneity and the number of
studies included, we investigated the influence of cyst
wall resection on the success rate.
After searching the databases mentioned above, we
identified a total of 606 articles: 192 from PubMed, 147 from
EMBASE, and 267 from OVID. Repeated studies, case
reports, reviews, and studies unrelated to the therapy of
popliteal cysts were excluded, and 58 articles were left.
After reviewing the abstract and full text, we screened
studies according to the inclusion and exclusion criteria
and finally included a total of 11 studies for
metaanalysis (Fig. 1) [
12, 15, 17, 21, 22, 27, 30–34
In 7 of the 11 studies, the communication between the
cyst and the articular cavity was enlarged by surgery; in
3 studies, the communication was closed; and in 1 study,
only intra-articular lesions were managed (Table 1). The
success rate was analyzed after pooling of data from
studies that involved communication-enlargement
surgery and those that involved communication-closure
surgery. Among the seven studies with communication
enlargement, cyst wall resection was performed in four
studies, and the cyst wall was left intact in three studies.
In all the seven studies, arthroscopy was employed to
treat the popliteal cyst, RL scoring was performed after
surgery, and average follow-up time was comparable
(Table 2). Thus, we further analyzed the influence of cyst
wall resection on the success rate. In the
communicationclosure group, the number of studies included was small,
the tools used for postoperative evaluation were
inconsistent, and the measures taken to manage the intra-articular
lesions were different; thus, the influence of cyst wall
resection on the success rate was not further evaluated
even though two studies reported cyst resection. The
patients’ characteristics are shown in Tables 2 and 3.
In addition, 10 of the 11 studies reported concomitant
intra-articular lesions in patients with popliteal cysts,
and the most common 2 lesions were medial meniscus
injury and articular cartilage injury.
Quality assessment of included studies
Of 11 studies included in this meta-analysis, 10 were
case series and 1 was a prospective clinical study [
Although there were controls in this prospective study,
its goal was to investigate the prevalence of popliteal
cysts and the incidence of concomitant intra-articular
lesions. This study included no comparator controls vs 20
patients with popliteal cysts. Thus, modified NOS was
still used to evaluate its quality.
In terms of study design, 11 studies were awarded a
total of 8 of a possible 22 stars. Only one study was
prospective, and the remaining designs were retrospective
or unknown. In addition, the inclusion and exclusion
criteria were described in 7 studies, which accordingly
were awarded 7 of 11 possible stars. In terms of
selection, 11 studies were awarded 4 of a possible 11 stars
because most of the case series were from the same
hospital and patients were not recruited consecutively.
In terms of outcome, studies were awarded 14 of a
possible 22 stars. Ultrasonography or magnetic resonance
imaging (MRI) was administered before and after
surgery in 7 studies, and their follow-up rate was higher
than 95 % in 7 studies. The mean number of stars
awarded to these studies was 2.36.
After pooling, the success rates of
communicationenlargement surgery and communication-closure surgery
were 96.7 % (95 % confidence interval (CI) 92.7–
98.5 %, I2 = 0 %, p = 0.7095, fixed-effects model) and
84.6 % (95 % CI 72.8–91.8 %, I2 = 0 %, p = 0.5295,
fixed-effects model), respectively (Figs. 2 and 3). The
meta-analysis showed that the success rates of cyst wall
resection group and non-cyst wall resection group were
98.2 % (95 % CI 94.0–99.5 %, I2 = 0 %, p = 0.6565,
fixedeffects model) and 94.7 % (95 % CI 86.0–98.1 %, I2 = 0 %,
p = 0.8248, fixed-effects model), respectively (Figs. 4
① enlargement of unidirectional valvular slits, ② closed the communication between the articular and the cyst, ③ correctly associated intra-articular disorders,
④ excision of the cyst or removal of the cystic wall
RL Rauschning and Lindgren knee score
aSimply correctly associated intra-articular disorders
bOnly 24 patients underwent a direct excisional cystectomy because the other 7 patients presented without fibrous structures
cAssociated intra-articular disorders were corrected only in a few cases
RL: Grade 0, 98 Grade 1, 13
RL: Grade 0, 40 Grade 1, 1
RL: Grade 0, 14
RL: Grade 0, 25 Grade 1, 5 Grade 2, 1
RL: Grade 0, 26 Grade 1, 1 Grade 2, 1 Grade 3, 1
RL: Grade 0, 7 Grade 1, 3
RL: Grade 0, 19 Grade 1, 10 Grade 2, 1
RL: Grade 0, 14 Grade 1, 5 Grade 2, 2 Grade 3, 1
Excellent: 12 Good: 8, Fair: 3, Poor: 2
Grade 0, 14 Clin. Exam. (Recurrent cyst), 1
Visual analog scale Score 1: 2 Score 2: 2 Score 4: 1
Score 9: 2 Score 10: 9
This meta-analysis included 11 studies: The
communication bridging the cyst and articular cavity was enlarged
in 7 studies [
12, 21, 22, 30, 32, 34
]; the communication
was closed in 3 studies [
17, 27, 33
]; and only
intraarticular lesions were managed in 1 study . The most
important finding of this study is that the current
literature on the treatment of popliteal cysts dose not support
one therapeutic method over another due to a lack of
high-quality studies. The aim of this study was to pool
the data on the treatment of popliteal cysts and
determine what is the most effective treatment option for
popliteal cysts based on the available literature. The
results showed that the success rate was 96.7 % in the
communication-enlargement group (no matter if the
cyst wall was resected or not). It remains to be seen
whether communication-closure surgery is effective, as
there is limited literature available on this topic.
Surgical interventions for the treatment of popliteal
cysts focus on the management of intra-articular lesions
and the communication bridging the cyst and articular
cavity, as well as cyst resection. However, open surgical
resections of cysts usually result in high recurrence rates
]. Thus, the therapy for popliteal cysts tends to treat
intra-articular lesions and to enlarge or repair the
communication between the cyst and the articular cavity. In
our meta-analysis, we identified a prospective study in
which only intra-articular lesions were managed, and
favorable therapeutic efficacy was achieved in only 5 of
16 patients during the follow-up period [
the number of patients studied was small, this finding
suggests that managing intra-articular lesions alone fails
to achieve favorable therapeutic efficacy.
While communication enlargement was the most
common primary treatment strategy, it was conducted
in 7 of the 11 studies in which not only the
communication bridging the cyst and articular cavity was
enlarged but the intra-articular lesions were also
12, 21, 22, 30–32, 34
]. After data pooling, we
determined that the success rate was 96.7 %. In addition,
all the studies employed arthroscopy. The RL score was
used after surgery, and statistical analysis showed I2 = 0 %
and p = 0.7095. Thus, we speculate that arthroscopic
management of intra-articular lesions and enlarging the
communication between the cyst and the articular cavity
are an effective strategy for the popliteal cyst. Sansone et
al. reported the arthroscopic approach to correct the
valvular mechanism by opening the connection after
removing the posterior horn of the medial meniscus in
1999, and this method also has been modified gradually
over time [
]. Ahn et al. found that surgeons could
identify the communication between the cyst and the
articular cavity using an arthroscope and could enlarge
the communication without resection of the posterior
horn of the medial meniscus [
]. Recently, Ohishi et al
] found that only the transverse slit was enlarged in
early studies [
18, 19, 21, 22, 34
], and they suggested that
enlarging the vertical slit was also important for the
therapy of popliteal cysts. Following the improvement of
techniques used to enlarge the communication between
the cyst and the articular cavity, the therapeutic efficacy of
treatments for popliteal cysts may improve.
In studies of communication-enlargement surgery, cyst
wall resection was reported in four studies [
21, 22, 32, 34
and patients in three studies did not receive cyst wall
12, 30, 31
]. Thus, we further investigated the
influence of cyst wall resection on the therapeutic outcomes
in popliteal cyst patients. The pooled results showed the
success rate was 98.2 % after cyst wall resection and
94.7 % in the absence of cyst wall resection. The success
rate in the cyst wall resection group was 3.5 % greater
compared to that of the non-cyst wall resection group.
Although there was good homogeneity in the studies
examined, we concluded only that cyst wall resection may
benefit patients with popliteal cysts because of the small
number of patients recruited. The success rate in the
absence of cyst wall resection was also as high as 94.7 %, and
thus, additional cyst wall resection may not significantly
increase the success rate. However, this result only
represents the success rate during the follow-up period
(25.2 months), and whether cyst wall resection can
improve the long-term efficacy requires confirmation from
studies with longer-term follow-up.
In three studies of communication-closure surgery, only
several patients received management of intra-articular
], but this approach was used in all patients in
two other studies [
]. After pooling outcomes data,
we found that the success rate was as high as 84.6 %,
which was improved significantly compared to outcomes
following the management of intra-articular lesions alone.
In the three studies mentioned above, the original surgery
was conducted in an open manner and employed simple
suture or using a proximally based flap from the
gastrocnemius tendon for additional reinforcement [
and later arthroscopic all-inside suture was used [
Of the 11 studies included in this meta-analysis,
arthroscopy was employed in 9 studies reported since 1999.
This suggests that arthroscopy has become the treatment
of choice for popliteal cysts because of its minimal
invasiveness and patients’ rapid postoperative recovery
regardless the approaches used. For example, Calvisi et al.
reported communication-closure surgery and the
management of intra-articular lesions by arthroscopy. Of 22
patients in this study, the success rate was 86.4 %, suggesting
favorable efficacy [
]. However, open surgery and
arthroscopy were employed for the therapy of popliteal cysts
in other available studies, the scoring tools used for
postoperative evaluation were different, and a total of only 62
cases were included. Thus, we could not draw any
conclusions on the efficacy in treating popliteal cysts. In addition,
the success rate which Calvisi et al. reported [
comparable to that of the non-cyst wall resection group
(94.7 %), but we cannot conclude that the efficacy of
communication-enlargement surgery is better than that of
communication-closure surgery, because this remains to
be validated by additional studies of arthroscopic
allinside suture of symptomatic popliteal cyst.
In 11 studies, investigators reported the incidence of
concomitant intra-articular lesions in patients with
popliteal cysts, and the results showed that injuries to the
medial meniscus and articular cartilage were the most
common lesions in the joint. These results remind us to
research more effective treatment methods of medial
meniscal injuries and articular cartilage injuries may
further improve the therapeutic outcomes for treatments of
popliteal cysts. In addition, the seven studies that we
reviewed also described the reasons for therapeutic
12, 15, 17, 22, 27, 30, 33
]. Rupp et al. reported that
postoperative cysts persisted in patients with
higherlevel articular lesions (grade 3 or grade 4), but cysts
disappeared in patients with lower-level articular lesions
]. In another 6 studies, therapeutic failure was
observed in 13 patients, of whom 5 had knee arthritis, 3
had malacia of the posterior tibial plateau, and 1 had
severe chondral defects [
12, 17, 22, 27, 30, 33
]. This not
only confirms the importance of managing
intraarticular lesions during surgery but also indicates that
the available methods used to treat severe arthritis and
cartilage defects are limited.
There were still limitations in this systemic review
and meta-analysis: (1) Non-English articles were
excluded from this analysis. (2) Included studies were
case series with low evidence levels; modified NOS was
employed for the evaluation of study quality, and low
scores were indicated for these studies. Future
highquality studies are required to confirm the efficacy of
surgical interventions to treat popliteal cysts. (3) Only
three studies included communication-closure surgery,
and only one study reported communication-closure
surgery and concomitant management of intra-articular
lesions by arthroscopy. Patients who received
arthroscopic communication-closure surgery were not further
subgrouped. Due to the lack of amount and
homogeneity of the literature, no conclusions can be drawn.
More studies are needed to investigate the efficacy of
communication-closure surgery in patients with
Based on the current available evidence, at present, any
how arthroscopic excision of the cyst wall, arthroscopic
management of intra-articular lesions, and enlarging the
communication between the cyst and the articular cavity
is an ideal strategy for the popliteal cyst. The pooled
success rates for communication-enlargement surgery and
communication-closure surgery were 96.7 and 84.6 %,
respectively; the pooled results showed the success rate was
98.2 % after cyst wall resection and 94.7 % in the absence of
cyst wall resection. The current literature on the treatment
of popliteal cysts is limited to retrospective case series, so
the results from this meta-analysis are not available to
support one treatment strategy over another. Future
prospective studies with high-quality methodology and
uniform scoring system are required to directly compare
communication-enlargement surgery and
communicationclosure surgery and determine the optimal treatment of
popliteal cysts. Cyst wall resection may improve the
therapeutic efficacy, to draw definitive conclusions, and
highlevel clinical researches with a large number of patients and
long-term follow-up should be initiated.
Newcastle–Ottawa quality assessment scale
Adjusted for case series by Zengerink et al. [
1. Type of study
d. Not described
a. According to protocol
b. Without protocol
c. No protocol described
1. Representatives of included patients
a. Truly representative of the average
communitydwelling chronic syndesmosis patient
b. Somewhat representative of the average
community-dwelling chronic syndesmosis patient
c. Group of patients selected by the surgeon
d. No description of the patient’s provenance
1. Assessment of outcome
a. Independent blind assessment
b. Record linkage
d. No description
2. Adequacy of follow-up
a. Complete follow-up—all subjects accounted for
b. Subjects lost to follow-up are unlikely to introduce
bias—e.g., a small number lost (<5 %)
c. Follow-up rate of <95 % and no description of
those lost to follow-up
d. No statement
NOS: Newcastle–Ottawa scale; RL: Rauschning and Lindgren knee score;
MRI: magnetic resonance imaging.
The authors declare that they have no competing interests.
ZXN and WJS made a contribution to designing the study and providing
critical revisions to this article. ZXN and BLH were responsible in writing the article.
ZXN, LB, and BLH examined the collected articles and made a contribution to
collecting the data. All authors read and approved the final manuscript.
The present study was supported by the National Natural Scientific Foundation
of China (grant no. 81272050) to LB. The authors are grateful to all the authors
of the studies included in the present study and their study participants.
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