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Synchronous septic arthritis of knee and mycotic aneurysm popliteal artery

Jafri A.A*., Fisher R#., Reed M.R.**

*Specialist Registrar Trauma and Orthopaedics, Wansbeck Hospital, Ashington, Northumberland
#Specialist Registrar Vascular Surgery, Freeman Hospital, Newcastle upon Tyne
**Consultant Surgeon Trauma and Orthopaedics, Wansbeck Hospital, Ashington, Northumberland

Address for Correspondence

Anwar A Jafri
20 Landsdowne Gdns, Jesmond Vale,
Newcastle, NE2 1HE, UK

J.Orthopaedics 2007;4(1)e11


We report an unusual presentation and subsequent management of a co-existent ipsilateral knee septic arthritis and mycotic popliteal aneurysm that ruptured .

Case Report:

A 56 year old man first presented to Accident and Emergency department 2 days after he slipped on wet paving sustaining a hyper-extension of the knee injury. He was able to walk immediately after the injury but noted gradually increased swelling and pain over the next 48hours

His past medical history was unremarkable apart from gout of the great right toe for which he took allopurinol. There was no other  past medical history or family history of diabetes or peripheral vascular disease. He was a non smoker.  Clinical examination revealed an antalgic gait, a moderate effusion of the knee, bony tenderness over the medial joint line and a reduced range of movement 0-60degrees. Distal neurovascular status was normal with palpable pedal pulses. AP and lateral radiographs of knee demonstrated no fracture.  He was treated for a soft tissue injury and discharged.

He represented 5 weeks later because of a  2 day history of malaise, lethargy, stiffness of the knee and increasing pain on mobilisation.

On assessment he was dehydrated, pyrexial (37. 9C) and tachycardic (HR117)  but normotensive. The right knee was found to be held in fixed flexion at 30 degrees, grossly swollen with a large, tense effusion with pain localised to medial joint line. The calf was not swollen or tender although a fullness around the popliteal fossa was noted.  Range of knee movement  was from 30-80 degrees. Distal examination revealed surgical scars of previous varicose vein surgery and hyper pigmentation of skin in the lower leg which was at the time thought to be consistent with chronic venous disease. The foot was warm, well perfused and dorsalis pedis and posterior tibialis pulses were palpable. Capillary refill was normal.

Laboratory based investigations revealed a neutrophil leucocytosis (WCC 22) and elevated CRP and ESR. Radiographs of knee AP and lateral showed early degenerative changes.

The knee was aspirated under aseptic conditions yielding 80ml of sero-sanguinous fluid which under microscopy was found to contain gram positive cocci.

Given the patients systemic inflammatory response he was resuscitated with intravenous fluid, commenced on empirical Flucloxacillin 2g and Benzylpenicillin 1.2g and taken to theatre for emergency arthroscopic washout of knee on the evening of admission

No tourniquet was used for the procedure, standard technique and portals (lateral and medial and supero-lateral draining) were used. Copious sero-sanguinous fluid containing white particulate tissue was drained. Systematic examination revealed florid synovitis and extensive loss of articular cartilage globally.

Immediately post–operatively  the patient was comfortable and noted to have palpable, pedal pulses both by operating surgeon and recovery staff. However 20 mins post-operatively the patient experienced acute, excruciating right leg pain. Symptoms of decreased sensation and cold foot then evolved over the next 30 mins. Examination revealed a cold foot with impalpable pedal pulses, poor capillary refill and a pulsatile popliteal fossa mass.

The patient was transferred as an emergency to the Regional Vascular Unit, where acute ischaemia secondary to thrombosis of a popliteal aneurysm was diagnosed. Abdominal aortic and contralateral popliteal aneurysms were excluded. Whilst awaiting emergency angiography the patient suddenly developed intractable pain in the lower leg with rapidly progressing swelling necessitating emergency surgery. Proximal and distal vessel control was established before the popliteal aneurysm was dissected. An arterial rupture was noted with thrombus throughout the popliteal fossa, but there was no evidence of a breach in the knee joint capsule. A specimen of thrombus was sent for culture and sensitivities. A normal popliteal artery was noted immediately proximal and distal to the ruptured aneurysm. Ligation of the aneurysm was followed by a superficial femoral to below knee popliteal bypass using contralateral reversed superficial femoral vein due to previous bilateral long saphenous ligation and stripping. Four compartment fasciotomies completed the procedure.

Post operative recovery was complicated by persistent intermittent pyrexia. Cultures from the arthroscopic washout and the intra-operative thrombus grew B haemolytic Streptococcus group B, with sensitivities to Amoxicillin and Gentamicin, which the patient was commenced on. Medical Microbiology reported this as an unusual aetiology for septic arthritis and expressed concern regarding sub-acute bacterial endocarditis as the aetiology. Echocardiogram was  normal. The patient continued to make progress with a viable, functional limb and had no further sequelae.

Discussion :

Mycotic  aneurysms account for 2.5-5% of all aneurysms.1  The popliteal artery is an infrequent site for such pathology, it is usually associated with atherosclerotic lesions and frequently associated with contra-lateral popliteal aneurysm and abdominal aortic aneurysms.2.This is an unusual presentation of coexistent mycotic aneurysm and septic arthritis. It has been described only on one previous occasion in 1972. 3. Features supporting the aneurysm being mycotic include its localised, saccular morphology in an otherwise normal artery. and the presence of the same unusual bacteria in ipsilateral knee joint and popliteal arterial wall. 4 It is unlikely that it was traumatic as the posterior joint capsule was intact and there was no evidence of iatrogenic damage.We postulate that the initial hyperextension injury caused damage to the popliteal arterial wall. A streptococcal bacteraemia then caused a localised arterial focus of infection. Bacteria was then disseminated into popliteal arterial tributaries supplying the synovium of the knee joint causing joint infection. The origin of the bacteria remains unanswered. The Vascular surgeons felt that a sub-acute thrombo-embolic process had occurred prior to presentation to the Accident and Emergency department and this was  clinically demonstrable by  subtle skin discolouration of lower leg. This was initially felt by the Orthopaedic team to be consistent with dermatological manifestations of venous stasis. The presentation of acute ischaemia may have been attributable to the characteristic features of a popliteal aneurysm:  sequential crural vessel embolisation with ultimate aneurysm thrombosis. This may have potentially been exacerbated by the septic arthritis and the arthroscopic procedure. This interesting case has highlighted that in the case of joint sepsis and distal skin changes one should consider aneurysms within the differential diagnosis.

References :

  1. Flammend F, Harris KA, DeRose G, Karam B, Jamieson WG. Arteritis due to Salmonella with aneurysm formation – 2 cases. Can J. Surg. 1992, 35;248-52.

  2. Wilson P., Fulford P, Abraham J, Smyth JV, Dodd PD, Walker MD. Ruptured infected popliteal aneurysm. Ann Vasc Surgery 1995; 9 497-9.

  3. Merry M, Dunn J, Weismann R, Harris ED.  Popliteal aneurysm presenting as septic arthritis and purpura. JAMA, July 3, 1972. Vol 221, No 1

  4. Bonds JW Jr, Fabian TC. Surgical treatment of mycotic aneurysm a case report and review of literature. Surgery 1985-98;979-82


This is a peer reviewed paper 

Please cite as : Jafri A.A:Synchronous septic arthritis of knee and mycotic aneurysm popliteal artery

J.Orthopaedics 2007;4(1)e11





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