Abstract
IntroductionThe role of popliteal cysts and subgastrocnemius bursitis in knee joint homeostasis is uncertain. The aim of this study is to describe cross-sectional associations between popliteal cysts, subgastrocnemius bursitis, knee symptoms and structural abnormalities in older adults.MethodsA cross-sectional sample of 900 randomly-selected subjects (mean age 63 years, 48% female) were studied. Knee pain, stiffness and dysfunction were assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire. Radiographic knee osteophyte and joint space narrowing (JSN) were recorded. Magnetic resonance imaging (MRI) was utilized to assess popliteal cysts, subgastrocnemius bursitis, cartilage defects and bone marrow lesions (BMLs).ResultsPopliteal cysts were present in 11.7% and subgastrocnemius bursitis in 12.7% of subjects. Subgastrocnemius bursitis was more common in those with popliteal cyst (36.2% versus 9.7%, P <0.01). In multivariable analyses, popliteal cysts were significantly associated with increased osteophytes in both medial and lateral tibiofemoral compartments while subgastrocnemius bursitis was associated with increased osteophytes and JSN in the medial tibiofemoral compartment. Both were significantly associated with cartilage defects in all compartments, and with BMLs in the medial tibiofemoral compartment. Furthermore, both popliteal cysts and subgastrocnemius bursitis were significantly associated with increased weight-bearing knee pain but these associations became non-significant after adjustment for cartilage defects and BMLs.ConclusionsPopliteal cysts and subgastrocnemius bursitis are associated with increased symptoms as well as radiographic and MRI-detected joint structural abnormalities. Longitudinal data will help resolve if they are a consequence or a cause of knee joint abnormalities.
Highlights
The role of popliteal cysts and subgastrocnemius bursitis in knee joint homeostasis is uncertain
Subjects with or without popliteal cyst were similar in terms of age, gender, Body mass index (BMI), non-weightbearing pain, total pain, prevalence of bone marrow lesion (BML), joint space narrowing (JSN) and effusion; subjects with popliteal cyst had more weight-bearing pain, and more osteophytes and cartilage defects at all sites
Subgastrocnemius bursitis was more common in those with popliteal cyst (36.2% versus 9.7%, P
Summary
The role of popliteal cysts and subgastrocnemius bursitis in knee joint homeostasis is uncertain. Osteoarthritis (OA) is a slowly progressive and multifactorial disease characterised by gradual loss of articular cartilage and other structural changes in the whole joint [1]. Among these structural changes, cystic lesions in the knee joint are a common feature seen on magnetic. Bursae are synoviumlined structures and normally quiescent, bursitis can be detected when bursae become inflamed and/or filled with fluid [3] Among those cystic lesions, popliteal cyst (Baker cyst [4]) and subgastrocnemius bursitis are most commonly detected on MRI with the prevalence of about 38% for popliteal cyst [5] and 15% [6] for subgastrocnemius bursitis. Subgastrocnemius bursae can communicate with the knee joint and popliteal cyst if co-existing
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