Weekly Case

Title : Case 666

Age / Sex : 19 / M

Chief complaint: Bilateral knee pain and swelling

What is your diagnosis?

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

Courtesy: 홍성환, Sung Hwan Hong, 서울대학교병원, Seoul National University Hospital



Ankylosing spondylitis (spondyloarthritis)



  1. Bilateral proximal tibiofibular arthropathy

- subchondral erosions, sclerosis and marginal bony proliferation on radiography

- subchondral bone marrow edema on MRI

  1. Enthesitis and synovitis of the left knee joint

- subentheseal (insertional) bone marrow edema at the patella and tibial tuberosity

- peritendinous edema around the distal quadriceps tendon

- increased knee joint effusion


Diagnosis: Ankylosing spondylitis (spondyloarthritis)



Inflammatory arthritis of the proximal tibiofibular joint is an uncommon but likely underdiagnosed cause of lateral

knee pain. Arthritis of this joint has been reported in connection with ankylosing spondylitis. Practitioners should be

careful to evaluate for arthritis as part of a work-up for chronic lateral knee pain and stiffness, and should consider

concomitant evaluation for spondyloarthritis. In this patient, plain radiography and MRI show subchondral erosion,

sclerosis, bone marrow edema and spur formation at both proximal tibiofibular joints. This patient has typical MR

findings of enthesitis at the anterior knee, which are also suggestive of spondyloarthritis.



  1. Hong HP, Chung HW, Choi BK, Yoon YC, Choi SH. Involvement of the proximal tibiofibular joint in ankylosing spondylitis. Acta Radiol 2009;50:418-422

  2. Canna SW, Chauvin NA, Burnham JM. A 17 year old with isolated proximal tibiofibular joint arthritis. Pediatr Rheumatol Online J 2013;11:1-4

Correct Answer
Total applicants 26 Correct answers 15
Name Institution
김기욱 국군수도병원, 전문의
김기욱 국군수도병원, 전문의
한유비 전문의
윤유성 순천향대 부천병원, 전문의
여현정 전문의
전인환 전문의
조영민 전문의
이규정 고대안암병원, 전문의
권기언 서울아산병원, 전문의
김성진 365병원, 전문의
박진희 서울아산병원, 전문의
이승보 서울아산병원, 전문의
최형인 군의관, 전문의
변홍권 서울아산병원, 전문의
김성윤 전문의
Semi-Correct Answer
Total applicants 26 Semi-Correct answers 2
강지희 전문의
안태란 길병원, 전문의