The Truth Behind Subchondral Cysts in Osteoarthritis of the Knee
Han Xinyun Audrey, Hamid Rahmatullah Bin Abd Razak*, Tan Hwee Chye Andrew
Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, 169608, Singapore
Subchondral cysts have always been taught to be one of the cardinal radiological features of knee
osteoarthritis but are not well understood. We aimed to evaluate the radiological prevalence and epidemiology of
subchondral cysts in patients with knee osteoarthritis to determine if they are truly a cardinal radiological feature.
All patients of a single surgeon with symptoms of knee osteoarthritis were selected for this study. All patients
had failed a trial of conservative therapy and were planned for total knee arthroplasty. Patients with symptoms of and
documentary evidence of inflammatory arthritis, other neurological and orthopaedic problems causing functional deficits
were excluded from this study. A total of 806 plain radiographs were analyzed with the aid of an atlas for the presence of
narrowed joint space, osteophytes, subchondral sclerosis and subchondral cysts. The radiological prevalence of each
feature was then calculated. Demographics and pre-operative measurements were compared between patients with and
without radiological evidence of subchondral cysts.
Subchondral cysts were only present in 30.6% of the study population. Narrowed joint space was present in
99.5%, osteophytes in 98.1% and subchondral sclerosis in 88.3% of all radiographs. The differences in prevalence were
statistically significant. There was a higher proportion of females in patients with radiological evidence of subchondral
cysts. These patients also had a greater varus deformity preoperatively.
With a radiological prevalence of 30.6%, subchondral cysts should not be considered a cardinal radiological
feature of osteoarthritis. Subchondral cysts may be associated with the female gender and genu varum.
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* Address correspondence to this author at the Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, 169608, Singapore;
Tel: (65) 9004-5495; Fax: (65) 6667-8701; E-mail: email@example.com