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)

Discussion

Findings:

1. Bilateral proximal tibiofibular arthropathy

- subchondral erosions, sclerosis and marginal bony proliferation on radiography

- subchondral bone marrow edema on MRI

2. 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)

Discussion:

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.

References:

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