This 55-year-old male presents with right knee pain, and his history indicates no known knee injury, surgery, or cancer.
Q1 – You are shown a sagittal T1 (image 1) and axial T2 (image 2) of the patella. What is wrong with the plate?
Q2 – What is the name of the plate indicated in question 1? The axial is key!
A1 – The plate is delaminating or separating anteriorly from a deformed patella (image 4, pink arrow).
A2 – The prepatellar plate. The prepatellar plate is analogous to the prepubic plate in the pelvis. The quadriceps descends composed of its four layers namely (a) the anterior rectus femoris, (b) the vastus medialis, (c) the vastus lateralis, and (d) the deep vastus intermedius.
The superficial rectus component continues along the anterior surface of the patella where it rejoins the patellar tendon, inferiorly. This is analogous to the rectus abdominis coursing over the prepubic surface, and joining the adductors below it.
When this separation of plate from pubis occurs in the pelvis, it leads to athletic pubalgia syndrome with, potentially, a sports hernia. In other words, pubic plate detachment is one of the causes of sports hernia syndrome.
In the knee, the prepatellar plate is overlooked. This patient has a patellar deformity that includes the following:
- Post-traumatic, post-fracture scar and remodeling (image 3, purple arrow)
- Separated inferior patellar tubercle buried within the patellar tendon (image 3, yellow arrow)
- Innumerable spurs (image 3, orange arrows)
Yet, despite all of this, it is the delamination or “peel” of the prepatellar plate from the undulating irregular anterior surface of the patella (image 4, blue arrows) that are causing the patient’s symptoms. Focal high signal deep to the plate is a helpful sign (image 4, pink arrow) of plate delamination.
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