Synovial Plica Syndrome of the knee were first described in the beginning of the last century.
Postmortem studies have shown plica to be present in 20–50% of knees, with the highest prevalence in individuals of Japanese descent.
There is some controversy regarding the prevalence of the plica syndrome, with some reports suggesting that it does not exist:
Jackson et al., Dandy, and others have stated that although plicae may indeed cause symptoms, the syndrome is overdiagnosed and many normal synovial plicae are removed.
Conversely, other authors consider the plica syndrome to be a common cause of anterior pain in the knee that is often misdiagnosed, and believe that a suprapatellar membrane is virtually never asymptomatic.
Knee Plica Anatomy
During fetal development, the knee is separated into three compartments by synovial membranes. At 4 to 5 months of development, the partitions resolve to form a single cavity. Incomplete or partial resorption results in incomplete synovial shelves or plica.
The three joints involved in the developing knee from which the remnants evolve are:
- the joint between the fibular and the femur;
- the joint between the tibia and the femur;
- the joint between the patella and the femur.
The most common plica in the knee is called the anterior or inferior plica, or mucous ligament. This plica is represented by tape-like fold running from the fat pad to the intercondylar notch of the femur and overlying the ACL.
The plicae to the medial and lateral sides of the patella, which run in a horizontal plane from the fat pad to the side of the patellar retinaculum, are referred to as the superomedial or superolateral plicae or the suprapatellar membrane, or the medial or lateral synovial shelf.
It has been suggested that symptomatic synovial plicae are one of the causes of anterior pain in the knee in children and adolescents.
Plica Syndrome Symptoms:
The plica syndrome has been associated with anterior pain as well as clicking, catching, locking, or pseudo-locking of the knee, and it may even mimic acute internal derangement of the knee.
Any condition that produces chronic irritation, trauma, or scarring may result in thickening of the plicae and the production of signs and symptoms internal derangement of the knee.
Sherman and Jackson have proposed a set of criteria for the Plica Syndrome diagnosis:
- History of the appropriate clinical symptoms.
- Failure of nonoperative intervention.
- Arthroscopic finding of a plica with an avascular fibrotic edge that impinges on the medial femoral condyle during flexion of the knee. This is often a diagnosis of exclusion and can only be confirmed at arthroscopy.
- No other abnormality in the knee that would explain the symptoms. It has also been suggested that a localized area of
chondromalacia at the site of impingement by a plica on the femoral condyle is evidence that a plica is the cause of the symptoms.
Plica Syndrome Test has been used to help in diagnosis of plica syndrome of the knee.
See Also: Plica Syndrome Test
The mediopatellar plica (also termed Lino’s shelf ), although the least common, this variety is often the cause of problems if it becomes thickened, resulting in pain with palpation over the medial parapatellar area (medial plica irritation). The severity of symptoms is not proportional to the size or breadth of the synovial plica.
There also appears to be no correlation between the duration of symptoms and the presence of pathologic changes in the plica.
A palpable band or snapping, especially over the medial femoral condyle, should be sought.
Several authors have noted an association between the presence of plica and the development of chondral lesions of the femoral condyle. These degenerative changes have been suggested to be caused by a pathological medial plica that snaps or impinges against the underlying femoral condyle during knee motion.
Plicae are not visualized well on plain radiographs, but a double-contrast arthrogram may demonstrate a suprapatellar
plica or an anterior plica.
A skyline radiograph may demonstrate a synovial shelf.
Dynamic ultrasonography has been reported to have a diagnostic accuracy of 88%, sensitivity of 90%, and specificity of 83% in the evaluation of medial plica syndrome; however, this technique is highly operator dependent.
Plica Syndrome Treatment
The conservative intervention for plica syndrome involves:
- stretching of the quadriceps, hamstrings, and gastrocnemius as well as isometric strengthening,
- patellar bracing,
- anti-inflammatory medication,
- and an altered sports-training schedule.
In an uncontrolled study, this type of intervention resulted in an improvement in 40% of patients over a 1-year period.
Injection of the synovial plicae with corticosteroids and a local anesthetic in another uncontrolled study was reported
to have an excellent result in 73% of patients.
Plica Knee Surgery:
When patients are truly symptomatic, or when conservative measures have failed, a plica knee surgery is done with surgical excision and it is usually curative.
Excision usually is done by arthroscopic techniques, although a limited excision can be performed through a medial parapatellar incision.
Simply incising or sectioning the plica is not recommended because of the possibility that the continuity of the plica will be restored by scar tissue.
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