A young male runner with a posterior knee mass—not just your typical Baker's cyst

Abstract

We present the case of a 28-year-old man with a growing mass in his right popliteal fossa causing pain on exertion. The differential diagnosis included Baker's cyst, entrapment syndrome of the popliteal artery, as well as a benign or malignant neoplasm. An ultrasound was non-specific. Follow-up MRI of the knee demonstrated cystic adventitial disease (CAD). With only about 500 cases reported in the literature since its discovery in 1947, CAD is a rare entity. The disease is characterised by mucinous or gelatinous cysts in the arterial or venous adventitia. The disease is predominantly seen in the popliteal artery and typically affects otherwise healthy males in the fourth to fifth decade of life. It presents clinically as intermittent exertional claudication. Examination of our case and a review of the literature will highlight the importance of considering CAD in patients who report of a popliteal mass and intermittent claudication.

Cystic adventitial disease of the popliteal artery presenting with features of entrapment syndrome

“…First described by Atkins and Key in 1947, CAD is a rare disorder, comprising 0.1% of vascular diseases. [2][3][4][5] It is characterized by the presence of an adventitial cyst resulting in lower extremity arterial stenosis and subsequent ischemic symptoms. The cysts are composed of an accumulation of mucinous fluid formed by proteoglycans, mucoproteins, mucopolysaccharides, hyaluronic acid, and hydroxyproline.…”

“…The cysts are composed of an accumulation of mucinous fluid formed by proteoglycans, mucoproteins, mucopolysaccharides, hyaluronic acid, and hydroxyproline. 2,5,6,8 Ninety percent of cases of CAD are unilateral, with involvement of the popliteal artery. [2][3][4][5][6] Less commonly, the external iliac, femoral, radial, ulnar, brachial, and axillary arteries are implicated.…”

“…2,5,6,8 Ninety percent of cases of CAD are unilateral, with involvement of the popliteal artery. [2][3][4][5][6] Less commonly, the external iliac, femoral, radial, ulnar, brachial, and axillary arteries are implicated. 2,3,5 Rare reports exist of CAD affecting veins.…”

“…[2][3][4][5][6] Less commonly, the external iliac, femoral, radial, ulnar, brachial, and axillary arteries are implicated. 2,3,5 Rare reports exist of CAD affecting veins. 3 Young to middle-aged generally healthy patients, particularly males, are mostly affected.…”

“…3 Young to middle-aged generally healthy patients, particularly males, are mostly affected. [3][4][5][6] The classic presentation consists of new-onset intermittent claudication of a lower extremity, with a recovery time longer than Table. Comparison of cystic adventitial disease (CAD) of the popliteal artery and popliteal artery entrapment syndrome (PAES)…”