Diagnosis: Synovial plica
The MRI with fat saturation revealed a symptomatic synovial plica between the patellar facet and the condyle (FIGURE 1, arrow). The normal x-ray findings had already ruled out osteochondritis dissecans of the femoral condyles, patellar abnormalities, and trochlear dysplasia; the MRI ruled out several additional items in the differential, such as damage to the meniscus, ligament, and/or cartilage.
The synovial plica is a normal structure that develops during the embryogenic phase; however, involution is incomplete in up to 50% of the population, resulting in persistent plicae.1 The plica is often located in a medial position but can occur lateral to, above, or below the knee cap. Although usually asymptomatic, the plica can become pathologic when irritation (eg, from repetitive motion) causes an inflammatory response.1
Synovial plica syndrome, as this condition is known, is a common cause of anterior knee pain in adolescents and athletes; incidence ranges from 3.8% to 5.5%.2 The patient often reports trauma (a direct impact to the knee) or participation in sports activities that require repeated flexion-extension of the knee.3
Presenting symptoms and MRI findings can unlock the diagnosis
The combination of anterior knee pain and a painful parapatellar “cord” on palpation is the most frequent diagnostic sign of synovial plica syndrome.1 Quadriceps wasting, intra-articular effusion, and reduced range of motion of the knee may also be observed.1,4 Some patients experience particularly disconcerting symptoms, such as knee locking, clicking, or instability.1
In most cases, MRI confirms the clinical diagnosis while ruling out other possible causes of the symptoms and associated pathologies.5 However, MRI may not reveal the plica if it is attached to the articular capsule or if there is no intra-articular effusion. Dynamic ultrasound might be of diagnostic value but is operator dependent.4
Continue to: If conservative treatment fails, consider surgical repair