Background Baker’s cyst (BC) is a fluid distension of the bursa between the gastrocnemius and semimembranosus tendons and is often observed in osteoarthritis of the knee. BC can be detected during clinical examination as a painful mass in the popliteal region or is reported as stiffness or pain, but it is often asymptomatic. BC’s rupture may mimic thrombophlebitis. Ultrasonography is emerging as a technique of choice for detecting popliteal cysts because of its ease and accuracy.
Objectives To assest the prevalence of Baker’s cyst in patients with chronic painful osteoarthritis of the knee, established on the basis of ultrasonographic evidence of popliteal effusion, and to evaluate the correlation between BC, severity of osteoarthritis and degree of joint effusion.
Methods A retrospective study was conducted on a cohort of gonalgia patients referred to us for ultrasonography of the knee. Examinations were performed by an operator experienced in musculoskeletal ultrasonography, using linear 5-13 MHz probes. The following parameters were considered: signs of osteoarthritis of the knee, namely marginal femorotibial osteophytosis, joint effusion and BC. A dichotomous score was assigned to each item (1 present, 0 absent). Severity of osteoarthritis and degree of joint effusion were also graded semiquantitatively from 0 to 3. The presence and degree of osteophytosis was used as criterion for ultrasonographic diagnosis of osteoarthritis and to assign a semiquqantitative score. The data was processed using logistic regression analysis and SPSS version 12 software.
Results 399 patients were studied; 293 patients(73.4%)showed sonographic features of osteoarthritis and 251 (62.9%) joint effusion. BC was found in 102 patients (25.8%) together with a positive association with sonographic features of osteoarthritis and joint effusion.
Conclusions Our data suggest a positive association between BC and osteoarthritis of the knee (with an increasing trend between prevalence and severity of osteoarthritis) and between BC and presence and degree of joint effusion, though statistical significance was not reached in either case. The method of joint ultrasonography proved to be a simple, fast and reliable auxiliary to clinical examination in the recognition of BC. All patients with osteoarthritis of the knee, especially advanced disease with joint effusion, should undergo ultrasonographic screening for BC.
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Disclosure of Interest None Declared
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