Lateral radiograph of the patient shows a well-circumscribed 2.5-by-2-cm oval calcification adjacent to the popliteal artery and posterior to the distal femur.
Anteroposterior radiograph of an 82-year-old man shows right knee osteoarthritis.
An 82-year-old man presents with a several-year history of right knee pain. He has been seen in the past for right knee osteoarthritis and has received steroid injections, which have worked well. Another steroid injection is planned, but lateral radiograph reveals a calcified mass in the back of the knee. The radiograph shows a well-circumscribed oval calcification 2.5 by 2 cm adjacent to the popliteal artery and posterior to the distal femur. Magnetic resonance imaging is ordered to differentiate between a soft tissue mass and a popliteal aneurysm and confirms the diagnosis of popliteal aneurysm.
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Popliteal artery aneurysm (PAA) is an abnormal dilation of the arterial wall that can cause life- and limb-threatening complications if the aneurysm bursts or clots. Thromboembolic events are the most frequent complication (occurring in 42%-77% of patients) and can lead to amputation in up to 20% of patients. PAAs account for 70% to 80% of all peripheral aneurysms and occur bilaterally in 50% of patients.
Although the exact etiology is unknown, the presence of arteriosclerosis is thought be the most significant contributor. Hypertension also adds mechanical stresses to the artery that can play a role in aneurysm formation.
Popliteal aneurysms will naturally expand over time, on average about 10% a year. Large PAAs expand faster than smaller ones. PAAs are often asymptomatic but as they enlarge, can cause pain, swelling, pulsation, and distal edema and venous thrombosis (if the aneurysm compresses the popliteal vein). The rate of complications is greatest with PAAs greater than 2 cm and increases with time (24% in 1 year, 35% in 4 years, and 74% in 5 years).
PAAs that are symptomatic and greater than 2 cm should be treated surgically. Anticoagulants have no effect on the growth of PAAs and observation alone will not prevent ischemia. Current surgical options include open or endovascular repair, both of which have similar success rates.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- Ghotbi R, Sotiriou A, Schönhofer S, Zikos D, Schips K, Westermeier W. Stent-graft placement in popliteal artery aneurysms: midterm results. Vascular Disease Management. http://www.vasculardiseasemanagement.com/article/7537. September 5, 2008. Accessed May 16, 2017.
- Dawson I, van Bockel JH, Brand R, Terpstra JL. Popliteal artery aneurysms. Long term follow-up of aneurysmal disease and results of surgical treatment. J Vasc Surg. 1991;13:398-407.