The reliability of the clinical examination for detecting Baker's cyst in asymptomatic fossa

Objective To compare physical examination and ultrasonographic (US) examination for detecting Baker's cyst (BC) in asymptomatic popliteal fossa. Methods Popliteal fossa was examined in a total of 220 knees in 110 patients with knee pain/osteoarthritis (OA) and non-OA individuals. Clinical examination was performed by two independent physicians and US examination was performed by a third blinded physician. Results Examiner A found 25 BC, examiner B found 30 BC in 220 knees examined (κ = 0.35; 95% CI; 0.14–0.56) and inter-observer reliability was moderate. When US examination taken as the reference, receiver operating characteristic analysis revealed an area under the curve of 0.58 (95% CI; 0.51–0.65) for examiner A and 0.57 (95% CI; 0.50–0.64) for examiner B, showing a weak agreement between physical examination and US assessment. Conclusion This study demonstrates that many patients may have BCs without any symptoms at the popliteal fossa and clinical examination of the popliteal fossa could not accurately detect BC. US examination of the popliteal fossa should be performed to detect BCs and this may recover the diagnosis.