Treatment for lateral patellar impingement syndrome with arthroscopic lateral patelloplasty: a bidirectional cohort study
Wu et al. Journal of Orthopaedic Surgery and Research
Treatment for lateral patellar impingement syndrome with arthroscopic lateral patelloplasty: a bidirectional cohort study
Tianhao Wu 0 2
Shiyu Tang 1
Fei Wang 0 2
0 Department of Orthopedics, The Third Hospital of Hebei Medical University , No. 139 Ziqiang Road, Shijiazhuang 050051, Hebei , People's Republic of China
1 Department of Orthopedics, First Central Hospital of Baoding , Baoding 071000, Hebei , People's Republic of China
2 Department of Orthopedics, The Third Hospital of Hebei Medical University , No. 139 Ziqiang Road, Shijiazhuang 050051, Hebei , People's Republic of China
Background: Anterior knee pain is one of the most common musculoskeletal complaints of young patients. We notice that some patients had normal femoral trochlear, medial and lateral patellar retinaculum, and special patellar morphology, which resulted in a series of symptoms in the flexion of the knee due to the impingement of the lateral articular surface of the patella with the femur. We firstly termed this pathologic process as lateral patellar impingement syndrome (LPIS). This ambispective cohort study was to explore the curative effect of arthroscopic lateral patelloplasty for early LPIS. Methods: Thirty-five early LPIS patients which underwent arthroscopic lateral patelloplasty were enrolled in our study. Evaluations consisted of pre- and postoperative symptoms, physical examinations, radiographs, and questionnaires. The Lysholm score, patellar suitable angle, patellar tilt angle, and patellar lateral shift were measured with the CT scan and Merchant X-ray film. The efficacy was graded as excellent, good, fair, and poor according to the patient's subjective evaluation. Results: The patients were followed up for an average of 41.1 ± 18.6 months. The efficacy results were excellent in 6, good in 26, fair in 2, and poor in 1. There were statistical differences in pre- and postoperative Lysholm scores (80.66 ± 5.51 vs 81.91 ± 6.21) (P < 0.05). The pre- and postoperative congruence angle, patellar tilt angle, and patellar lateral shift were significantly different (P < 0.05). Conclusions: Arthroscopic lateral patelloplasty is an effective and minimal-invasive method for patients with lateral patellar impingement syndrome.
Lateral patellar compression syndrome; Lateral patellar impingement syndrome; Lateral patelloplasty; Arthroscopy
Anterior knee pain is a common musculoskeletal
complaint seen daily in the practices of primary care
physicians, rheumatologists, and orthopedic surgeons
], and persistent pain may affect the patient’s
daily life. Anterior knee pain may originate from
increasing venous engorgement in the patella, an
abnormal patellofemoral rhythm and pressure, and elevated
subchondral bone pressure [
]. Lateral patellar
compression syndrome (LPCS) is a syndrome caused
by abnormally high pressure in the lateral
patellofemoral joint, and it is secondary to non-dislocation of
the long-term patellar ectopic, contracture of the
medial patellar retinaculum, or fibrosis of the lateral
retinaculum. For patients with LPCS, we considered
that the force exerted on the surface of lateral
patellar joint might increase with the flexion of the knee
joint. The lateral articular surface of the patella
collides with the femur and produces a series of
symptoms similar to LPCS, which we define as lateral
patellar impingement syndrome (LPIS). There are
many causes of LPIS, including dysplasia of the
femoral trochlear, abnormal patella and lateral
retinaculum, and special patellar morphology.
A common procedure designed to alleviate the
pathologic forces on the patella in LPCS is an open surgery or
arthroscopic lateral retinacular release. For early and
mid-term LPCS, the main treatment is open or
arthroscopic lateral retinacular release which can restore the
patellofemoral joint and correct patellar tilt and thus
reduce the pressure of the articular surface of the patella
and relieve symptoms. However, the incidence of
postoperative hematoma in the open or arthroscopic lateral
retinacular release can reach 15–65% [
]. The most
significant complication is iatrogenic medial patellar
subluxation, which can aggravate the patient’s knee pain
and require further stabilization procedures [
addition, the traditional arthroscopic release does not
extend distal enough to relieve the pressure in flexion
. Arthroscopic debridement and cartilage drilling may
only have a limited effect on the local localized cartilage
injury, and the effect of debridement is short.
We hypothesized that arthroscopic repair of patellar
morphology without injury to the lateral support band
can change the relationship of the patellofemoral joint
and avoid the occurrence of the above complications.
This ambispective cohort study was designed to
investigate the efficacy of arthroscopic repair of patellar lateral
morphology in the treatment of early LPIS.
From June 2007 to June 2015, we performed a
bidirectional cohort study of patients with LPIS who underwent
anterior knee pain. The clinical manifestations included
aggravated pain upon ascending/descending stairs,
squatting down, or standing up; occasional bowstring, soft legs,
and other symptoms; patellar peripheral finger tenderness;
poor patellar mobility; and a sense of joint friction during
activities. Ethical approval was given by the Medical Ethics
Committee of the Third Affiliated Hospital of Hebei
Medical University, Shijiazhuang, China. Written
informed consent was obtained from all participants.
The inclusion criteria include age less than 50 years;
Kellgren and Lawrence grade was 0, I, II; normal femoral
block and lateral retinaculum; patients treated only with
oral medication, intra-articular injection of sodium
hyaluronate, and other conservative treatment; types III and
IV patella with symptoms of pain but without physical
signs; and types III and IV patella with symptoms of pain
and physical signs.
Exclusion criteria include meniscus injury, ligament
injury, malunion after patellar fracture, and other
mechanical factors; patients with intra-articular loose bodies;
symptoms mainly concentrated in the space of
tibiofemoral joint; abnormity in extension apparatus of knee,
such as TT-TG spacing > 20 mm and Q angle > 20°;
rheumatoid arthritis and other autoimmune diseases;
tuberculosis and other infectious arthritis; and other diseases
which were not suitable for surgery. Patients with previous
knee surgeries were excluded.
All surgical procedures were performed by one
highqualified orthopedic surgeon. After combined
spinalepidural anesthesia, the surgical sites were disinfected
and draped according to standard procedures. Tourniquet
was inflated (300 mmHg) when the knees were in a flexed
position, and then blood was driven to eliminate the
influence of tourniquet on muscle tension and position of the
thigh. Arthroscopy (stryker 10°, 30°) was placed through
the anterolateral approach (Fig. 1a) while the surgical
instruments were placed through the anterolateral
approach. After removing the synovial membrane of the
patella with a planer, the morphology of patella and the
matching relationship between the patella and
patellofemoral articular cartilage was observed. Then the
congruence of patellar trajectory and patellofemoral trochlea was
observed in the course of flexion and extension. Other
knee diseases such as patellar periosteal fold and
hyperplastic bone were removed under arthroscopy. The lateral
margin of the Wiberg types III and IV patella was
trimmed and polished to type II or even close to type I
with a drill. During the trim of the outer edge, the knee
activities of flexion and extension were continuously
performed. The contact situation between the lateral margin
of the patella and femoral trochlear lateral condyle and
the patellar tracking was observed under arthroscopy.
With 0°, 30°, and 90° of patella tangent perspective, the
trim of lateral margin of the patella was suspended until
the dynamic matching reached satisfactory recovery.
Albanese et al. [
] confirmed the removal of 25% of the facet
joints of the medial or lateral patellar, does not affect the
normal biomechanical function of the patellofemoral joint,
so the maximum patching of the patella is not more than
25%. The tourniquet was released after electrocoagulation
with the radiofrequency system. After complete
hemostasis and routine washing, the full-thickness skin
was sutured with 2-0 thread (Fig. 1b). Then compression
bandage was used.
Immediately after awakening, the patients began the
lower limbs muscle strength exercise, such as straight
leg raising quadriceps exercise as well as ankle flexion
and extension. To prevent joint adhesions and scar
contracture, knee flexion and extension exercises (range
from 0 to 90°) were conducted for 3 days immediately
after surgery; thereafter, a greater angle was encouraged.
Partial weight-bearing walk with the aid of crutch began
on the second day after surgery. A week after surgery,
the patients began full weight-bearing walking. Normal
physical activity can be resumed about 1 month after
surgery. Early physical exercise was encouraged if the
quadriceps strength and the angle of flexion and
extension were big enough.
Follow-up and therapeutic evaluation
All patients were followed up regularly through
outpatient service at 1, 3, 6, 12 months, etc. The patients’
medical history was collected, including sex, age,
duration of symptoms, lesion location, pathogenesis,
predisposing factors, history of surgery, and history of trauma.
Hospitalized patients were routinely evaluated for
Lysholm knee scores. Specialist examinations including
knee activity, with or without stretch flexion disorders,
friction and friction sound, with or without effusions,
bone rubbing and abnormal activity, and patellar
trajectory were performed. All patients underwent X-ray at
the positive lateral of the knee joint, Merchant X-ray
film, CT scan and magnetic resonance imaging, and
routine preoperative inspection.
The Lysholm knee score was obtained at the time of
follow-up, and the subjective response to ALP was
inquired. The efficacy was graded as excellent, good, fair,
and poor according to the patient’s subjective evaluation.
Postoperative patellar mobility, with or without joint
swelling, joint effusion, effusion, and joint stiffness were
recorded. X-ray at the positive lateral of the knee joint
and MRI was reexamined.
Patellar suitable angle (PSA), patellar tilt angle (PTA),
and patellar lateral shift (PLS) were measured according
to the patellar axial radiograph of Merchant method and
double-knee CT slice.
Normally distributed continuous variables were expressed
as mean ± standard deviation (SD). Statistical analysis was
determined by SPSS 12.0 software (SPSS Inc., US).
PreFig. 2 MRI features of the patients before surgery
and postoperative Lysholm score, CA, PLS, and PT of the
35 patients were compared by the paired t test. P < 0.05
was considered statistically significant.
Thirty-five patients were enrolled in our study, and the
demographic information was listed in Table 1. No
infection, joint effusion, effusion, and joint activity
limitation were observed during follow-up. Two patients with
severe osteoarthritis were treated with total knee
arthroplasty at 35 and 40 months after surgery, respectively.
One patient underwent surgical treatment of the
patellofemoral ligament 11 months after surgery because
of the recurrence of pain.
Obvious abnormal patellar morphology was observed in
all of the 35 patients during surgery, 23 cases with lateral
patellar cartilage injury and 19 cases with lateral superior
cartilage injury of the femoral condyle.
As shown in Table 2, the difference between
preoperative and postoperative Lysholm scores was statistically
significant; the mean postoperative Lysholm score was
1.25 higher than that before the operation.
All the patellofemoral joints were well aligned, and
the patellar morphology was normal in 35 patients
with knee CT at follow-up. The results of the
preoperative and final follow-up were shown in Table 2.
All patients had improved PSA, PTA, and PLS; the
preoperative and postoperative scores were statistically
significant. The knee and patellar joint were
significantly improved in 35 patients. Preoperative MRI was
shown in Fig. 2. Preoperative and postoperative X-ray
films of the patients were shown in Fig. 3.
Clinical symptom and functional status
Of the 35 patients who received follow-up, 3 had slight
dislocations in the patella. All patients returned to normal
daily life after 2 months. The subjective evaluation of the
surgical curative effect was shown in Fig. 4. We assessed
fair and poor as surgical failure, failure group accounted
for 8.6%, so the success rate was 91.4%. The patient with
poor treatment effect underwent surgical treatment of the
patellofemoral ligament 11 months after surgery because
of the recurrence of pain. One of the two neutral patients
received total knee arthroplasty at 35 months
postoperatively. Typical cases were shown in Fig. 5.
The lateral articular surface of the patella collides with
the femur and produces a series of symptoms similar to
LPCS, which we firstly define as lateral patellar
impingement syndrome (LPIS). We firstly introduced the
procedure of arthroscopic repair of patellar morphology to
the treatment of LPIS and achieved good results. In the
current study, a total of 35 early LPIS patients were
included and arthroscopic repair of patellar lateral
morphology was conducted. After surgery and reasonable
functional exercise, all patients received improved PSA,
PTA, and PLS; the success rate of the subjective
evaluation was 91.4%. The CT results of all patients indicated
that the patellofemoral joints were well aligned, and the
patellar morphology was normal at follow-up.
Previously, Arnoldi et al. [
] presented the concept that
a reduction of the intraosseous pressure may lead to pain
relief. Deliss [
], Morscher [
], and Heijgaard and
] observed relief of patellofemoral pain
following patellar osteotomy. Similarly, Wolter et al. carried out
a successful patellar decompression by fan-shaped drilling
in conjunction with cartilage shaving via knee arthrotomy
under general anesthesia [
]. The arthroscopic repair of
patellar morphology in our current study leads to an
immediate reduction of intraosseous pressure and pain relief.
Compared with the above surgical methods, our
technique is more minimally invasive and safe. Unlike medial
and lateral patellar retinaculum plasty, this method does
not require a large incision, avoids the injury to the soft
tissue and blood vessels such as the lateral superior
genicular artery, and reduces the risk of hematoma formation
Age less than 50 is an indication for this operation
because patellofemoral pain resulting from developmental
abnormalities is usually more severe in people over
50 years of age. Normal morphology of the femoral
trochlear and lateral retinaculum is also indications for
the operation because the lesions of patients with
trochlear dysplasia are not located in the patella, and the
repair of patellar morphology is not effective for the
disease. In addition, good medial and lateral retinaculum
are indications for this operation because only simple
patellar morphology repair is not effective for patients
with medial and lateral retinaculum injuries, and it is
necessary to adjust the soft tissue balance in order to
achieve effective treatment. However, the abnormality of
the knee extension apparatus is the contraindication of
this operation, because when the TT-TG space or Q
angle is too large, it is necessary to balance the soft
tissue to correct the patellar displacement, and simple
repair of bone morphology is incomplete for disease
control. Finally, Kellgren and Lawrence grade above III
is a contraindication of this operation because of the
severe cartilage abrasion in these patients, and the patellar
morphology repair and balance of soft tissue are
Although the clinically necessary amount of release
is not known with certainty, extending the release
distally to the level of the tibiofemoral joint line does
result in a measurable increase in patellar mobility. It
is not easy to control the lateral retinacular release,
and insufficient or excess loosening occurs frequently,
which leads to the failure of postoperative collision
remission and the occurrence of iatrogenic medial
patellar subluxation [
]. In a biomechanical
comparison of lateral releases, Marumoto et al. found that
effective release of the patellar lateral restraints, when
extended down to the tibial tubercle, was significantly
increased compared with a release that extends only to
the level of the anterolateral inferior arthroscopic portal
. In a prospective double-blinded comparative study,
Pagenstert et al. compared the complication rates and
outcome of open lateral retinacular (LR) lengthening and
open LR release in the treatment of LPCS, retinacular
lengthening showed less medial instability, less quadriceps
atrophy, and a better clinical outcome at 2 years compared
with retinacular release [
There are some limitations in our study: (1) lack of
control group; (2) the influence of the patellar plica and the
degree of joint degeneration on the evaluation of knee
function were not considered, and the surgical results of
LPIS patients should be graded according to the
degeneration stages of patellofemoral cartilage; (3) due to short
follow-up time, the long-term effect of the surgery was not
obtained; and (4) further biomechanical experiments are
This study was designed to investigate the efficacy of
arthroscopic repair of patellar lateral morphology in the
treatment of early LPIS. During our study, patients were
followed up for 41.0 months (10~78 months). There were
statistical differences in pre- (80.66 ± 5.51) and
postoperative (81.91 ± 6.21) Lysholm scores. The pre- and
postoperative congruence angle, patellar tilt angle, and patellar
lateral shift were (+ 27.71 ± 8.86)° and (+ 10.80 ± 8.17)°,
(11.60 ± 3.44)° and (10.86 ± 3.16)°, and (12.29 ± 2.37) and
(8.77 ± 2.18) mm, respectively. Arthroscopic lateral
patelloplasty is an effective, essential, and minimal-invasive
method for patients who suffered from lateral patellar
impingement syndrome. Further biomechanical
experiments are needed for more solid theoretical basis.
LPIS: Lateral patellar impingement syndrome; PLS: Patellar lateral shift;
PSA: Patellar suitable angle; PTA: Patellar tilt angle
No external funding was received.
Availability of data and materials
The datasets used and/or analyzed during the current study are available from
the corresponding author on reasonable request.
FW designed the study. TW and ST performed the experimental work.
ST evaluated the data. TW wrote the manuscript. All authors read and
approved the final manuscript.
Ethics approval and consent to participate
This study was approved by the Third Hospital of Hebei Medical University
and followed the Declaration of Helsinki and was approved by the ethics
committee of the Third Hospital of Hebei Medical University. Informed consent
were received from all patients.
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published
maps and institutional affiliations.
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