貝克氏囊腫在原發性疼痛退化性膝關節炎之發生率：骨骼肌肉超音波研究

Prevalence of Baker's cysts in painful primary osteoarthritis of the knee: a musculoskeletal ultrasound study

目的：調查原發性疼痛退化性膝關節炎病患中，貝克氏囊腫的盛行率。方法：對於150位根據美國風濕學會準則診斷的原發性疼痛退化性膝關節炎病患，進行臨床與骨骼肌肉超音波的研究探討。分析貝克氏囊腫與變數如關節積液、滑膜炎、骨刺及X光分級的關係。結果：藉由骨骼肌肉超音波，我們發現在254個膝關節中有54個膝關節（21.2%）有貝克氏囊腫（或在150個病患中有40個病患（26.7%）具有貝克氏囊腫）。在54個貝克氏囊腫中，只有18個（33.9%）臨床上有被診斷出來。在54個貝克氏囊腫中，其中有一個破裂。關節積液、滑膜炎、骨刺在膝關節偵測出來的比例分別是59.8%、30.3%及48.8%。貝克氏囊腫的盛行率與關節積液及滑膜炎有高度重要的關連性（p<0.001及p<0.001）。而骨刺及X光分級與貝克氏囊腫的盛行率也有重要的關連性（p<0.01及p<0.05）。結論：貝克氏囊腫在退化性膝關節炎的病患中是常見的，而且它們在臨床檢查中易被忽略，貝克氏囊腫也可能造成併發症。因此，臨床醫師應常用骨骼肌肉超音波來診斷貝克氏囊腫。

Objectives: To investigate the prevalence of the Baker's cyst in patients with primary painful knee osteoarthritis (OA). Methods: Prospective clinical and musculoskeletal ultrasound (MUS) findings in 150 patients with primary painful knee OA diagnosed by ACR criteria were studied. The relationship between the Baker's cyst and the variables joint effusion, synovitis, osteophytes and radiological grades of Kellgren and Lawrence were analysed. Results: Baker's cysts were demonstrated by MUS in 54 (21.2%) of 254 knees or 40 (26.7%) of 150 patients. Only 18 (33.9%) of 54 cysts had been diagnosed clinically. One of the 54 cysts ruptured. Joint effusion, synovitis and osteophytes were detected in 59.8%, 30.3% and 48.8% of knees respectively. There was a highly significant correlation between the presence of Baker's cyst with knee effusion and synovitis (p<0.001 and p<0.001, respectively). There was also a significant correlation of the presence of Baker's cyst with osteophytes and the radiographic grade (p<0.01 and p<0.05, respectively). Conclusion: The results indicate that Baker's cysts are common in knee OA, and that they may be missed clinically. Therefore, MUS should be more widely employed by clinicians in the diagnosis of Baker's cysts, which may sometimes be accompanied by significant morbidity.