Weekly Case

Title : Case 462

Age / Sex : 53 / M



Chief complaint: Intermittent
left knee pain (onset: 2 years ago)


What is your impression? 


Two weeks later, you can see the final diagnosis with a brief discussion of this case. (Please submit only one answer)


Courtesy: Sang Min Lee, Bundang Medical Center, CHA University



Diagnosis:

Synovial lipoma arborescence



Discussion





Findings:



- Diffuse
hypertrophy of the synovium is seen in the joint space with diffuse contrast
enhancement.



- Fatty
villous proliferation of the synovium is also seen in the suprapatellar recess
and infrapatellar recess. And multifocal small fatty signals are seen in the
hypertrophied synovium.



- Multiple
marginal erosions are also noted on the medial and lateral femoral condyles,
and medial and lateral tibial plateau and erosions are also seen in the
intercondylar fossa of femur.



- Peripheral
fatty signal of a few erosions is also seen.



- Small amount
of subsemimembranous–subgastrocnemius bursal effusion with synovial hypertrophy
is also seen.



 



Differential Diagnosis:



- Synovial proliferative disease (e.g., Rheumatoid
arthritis, synovial osteochondromatosis, pigmented villonodular synovitis) combined
with synovial lipoma arborescence



 



Diagnosis:
Synovial lipoma arborescence with diffuse synovitis and multifocal bony
erosions



 



Discussion:



1. Synovial lipoma arborescence



1) Rare benign
intra-articular mass



- Characterized by
“tree-like” (arbo = tree in Latin) fatty proliferation



- Involving
connective tissue of synovial membrane



- Mostly affects
suprapatellar bursa in patients in fifth to seventh decades



- Usually
unilateral



2) Etiology is unknown



- Reactive changes
of synovium due to trauma or inflammation



- Commonly
associated with degenerative arthritis or rheumatoid arthritis



- Secondary type
is more common in adult population, while primary type is predominantly seen in
younger population



3) Clinically, patients present with
painless joint swelling and effusions



4) Laboratory
findings, including joint fluid analysis for crystals and culture, and
generally unremarkable



5) Definitive
treatment is synovectomy



 



2. Characteristic MR Imaging Finding



1) Frond-like
synovial proliferation with fat signal intensity on all sequences



- Best seen on
T1-WIs or fat-suppressed T2-WIs



- Typically a
diffuse synovial process (diffuse synovial lipoma), but may present as a focal
synovial-based lipomatous mass



- Associated
findings:



       
Joint effusion: very common



       
Degenerative changes: common



       
Meniscal tears: common



       
Synovial cysts : uncommon



       
Bone erosions : uncommon



       
Chondromatosis: uncommon to rare



       
Patellar subluxation: rare



       
Discoid meniscus: rare







Correct Answer
Name Institution
Total applicants:38
Correct answers:22
박준동:청주뿌리병원, 전문의
최형인:서울대학교병원, 전공의
이승훈:한양대병원, 전문의
신재환:서울백병원, 전공의
이하연:최병원, 전문의
박지원:대구참튼튼병원, 전문의
조신영:웰튼병원, 전문의
김태형:건국대학교병원, 전공의
김지현:하이병원, 전문의
김동환:분당제생병원, 전공의
김준성:고대안암병원, 전공의
이지현:병무청, 전문의
강건우:군의관, 전문의
이문영:비앤피병원, 전공의
오은선:삼성서울병원, 전문의
김재현:서울대학교병원, 전공의
김환용:벌교삼호병원, 전문의
한유비:CMC, 전공의
김성관:국군수도병원, 전문의
윤성현:분당서울대학교병원, 전공의
하종수:샘병원, 전문의
노정현:단국대학교 병원, 전공의
Semi-correct answers:4
전성희:중앙보훈병원, 전공의
김보람:서울대병원, 전공의
김아람:서울바른병원, 전문의
이지은:안산예스병원, 전문의

Comment