We report an unusual presentation
and subsequent management of a co-existent ipsilateral knee
septic arthritis and mycotic popliteal aneurysm that ruptured .
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
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.
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.
Flammend F, Harris KA, DeRose G, Karam B,
Jamieson WG. Arteritis due to Salmonella with aneurysm formation
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Wilson P., Fulford P, Abraham J, Smyth JV,
Dodd PD, Walker MD. Ruptured infected popliteal aneurysm. Ann
Vasc Surgery 1995; 9 497-9.
Merry M, Dunn J, Weismann R, Harris ED.
Popliteal aneurysm presenting as septic arthritis and purpura.
JAMA, July 3, 1972. Vol 221, No 1
Bonds JW Jr, Fabian TC. Surgical treatment
of mycotic aneurysm a case report and review of literature.