(Fig 4-C.12) Acute Injury of Infrapatellar Plica

https://youtu.be/_q8Gn-CFCHs

https://youtu.be/EiNzQqJbmYs

 

 

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📌 Acute Injury of Infrapatellar Plica

 

• Acute injury to the infrapatellar plica can cause hemarthrosis, pain, and a locking sensation in the knee. 
• These symptoms usually follow trauma or repetitive knee motion.

 

✅ MRI Findings

• Sprain: Increased signal along the infrapatellar plica (IPP) on fluid-sensitive sequences, less than fluid signal intensity[1].
• Tear: Increased signal along the IPP with fluid signal intensity on fluid-sensitive sequences[1].
• Edema: Edema within the infrapatellar fat pad in a characteristic curvilinear pattern along the course of the plica[2].
• Hoffa’s Fat Pad: Tears appear as a linear high signal intensity zone on fat-suppressed T2-weighted images, not corresponding to normal Hoffa’s clefts[3]. Scars appear as low signal-intensity tissue on all sequences[3].

 

✅Differential Diagnosis

 

• Synovial Clefts: Two synovium-lined clefts in Hoffa’s fat pad, one vertical and one horizontal, are normally present. These clefts are smoothly marginated and follow a continuous curvilinear pattern[1].
• Sprain vs. Tear: Sprain or tear hyperintensity typically has ragged or irregular margins, unlike the smooth margins of synovial clefts[1].
• Horizontal Synovial Clefts: Differentiated from an IPP tear by their continuous nature with the joint cavity and roof formation by the IPP[1].

 

✅ Associated Injuries

• Infrapatellar plica tears often coexist with other knee injuries, especially ACL tears. 
• Edema and scarring of Hoffa’s fat pad are common in knees with torn ACLs due to instability and fat pad impingement around the ligamentum mucosum. 
• Abnormalities in Hoffa’s fat pad, such as focal and diffuse edema, tears, scars, and synovial proliferation, are more frequent in knees with ACL injuries[4].

 

References

1. SA J Radiol. 2021 Feb 19;25(1):1973
2. MRI Web Clinic — November 2018 Synovial Plicae of the Knee
3. Skeletal Radiol (2008) 37:301–306
4. Skeletal Radiology (2020) 49:823–836

 

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