The authors present a case of a 22-year-old man complaining of anterior knee pain and no history of trauma.
A computed tomography (CT) and a magnetic resonance imaging (MRI) were performed demonstrating two patellar layers, one anterior and one posterior, on both knees, confirming the diagnosis of bilateral DLP (Figure 1 and 2). In this case, cartilage tissue was found between the two layers and there was no significant condropathy (Figure 3 and 4).
The anterior osseous patellar layer attached to the extensor mechanism.
On MRI with fat suppression on DLP (Figure 4), both knees show a fluid like signal and abnormal convex posterior margin replacing the normal suprapatellar fat pad. These imagiological findings suggest suprapatellar impingement which was assumed to be the cause of the pain.
An all body x-ray was also performed and there were no signs suggesting association with multiple epiphyseal dysplasia (MED).
The DLP is a rare entity [1] that consists of two distinct patellar layers, one being anterior and one posterior.
The literature admits frequent association of DLP with autosomal recessive form of multiple epiphyseal dysplasia (MED) [2, 3]. An all body x-ray should be performed to exclude signs of MED.
Patients with DLP may be asymptomatic and the abnormally is often discovered incidentally on X-ray or CT studies. However, when the interface between the two layers is unstable, it can cause pain and sensation of subluxation. The abnormality of the normal patellar anatomy can affect the extensor mechanism and, although we didn't find any literature to support this statement, having this case in mind, we believe it can cause inflammation of the suprapatellar fat pad.
X-ray, CT and MRI are the main diagnostic imaging studies for this pathology, with the x-ray and the CT playing important roles in the characterization and identification of the two layers. On the other hand, MRI has an important role in the characterization of the cartilage and the soft tissue involvement.
Imaging techniques are important to rule out other differential diagnosis, such as multipartite patella and old frature, because they demonstrate the orientation of the two bone patellar layers. In addition, MRI is helpful to confirm the presence of cartilage.
Due to the rare incidence of this syndrome, its treatment is not standardized. However, when pain is an important complain, surgical approach with fusion between the two layers has been an option [1].
Bilateral double layered patella
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Based on the provided CT and MRI images, two main bony structures can be observed in the patellar region, located anteriorly and posteriorly, suggesting an abnormal patellar morphology. On the CT axial view, a “double-layer” phenomenon is visible within the patella, with a clear interface and bone density similar to normal bone. A complete cortical margin can be seen. In the sagittal and axial MRI sequences, there is a cartilaginous structure between the bony layers, along with mild inflammatory or edematous signal changes (demonstrated as high signal on T2-weighted images) in adjacent soft tissues (e.g., the suprapatellar fat pad).
No obvious fracture lines or traumatic lesions are identified, and no significant large-scale soft tissue tears are noted. The surrounding joint structures (including the femoral condyles and the tibial plateau, as well as their cartilaginous surfaces) appear essentially normal. There is no evident large joint effusion.
Taking into account the patient’s youth, lack of trauma history, clinical symptoms (anterior knee pain), and imaging findings (layered patellar structure, cartilage connection, and differentiation from common traumatic or developmental conditions), the most likely diagnosis is: Duplicated Layered Patella (DLP). To rule out epiphyseal abnormalities associated with multiple epiphyseal dysplasia (MED), further full-body skeletal X-rays or related investigations are recommended.
Conservative Treatment:
Surgical Treatment:
This report is for reference purposes only and does not replace in-person consultation or professional medical advice. If you have further concerns or if your symptoms worsen, please seek medical attention promptly for individualized care.
Bilateral double layered patella
