Lubricating ability of aspirated synovial fluid from emergency department patients with knee joint synovitis

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J Rheumatol. 2004 Mar;31(3):557-64.

Lubricating ability of aspirated synovial fluid from emergency

department patients with knee joint synovitis.

Jay GD, Elsaid KA, Zack J, K, Trespalacios F, Cha CJ,

Chichester CO.

Department of Medicine, Brown University School of Medicine, Rhode

Island 02903, USA. gregory_jay_MD@...

OBJECTIVE: To determine if joint effusions encountered in the emergency

department (ED) requiring arthrocentesis possess normal lubricating

ability or evidence cartilage degeneration. Chondroprotection of

articulating joint surfaces is provided by lubricin, a mucinous

glycoprotein that is a product of megakaryocyte-stimulating factor gene

(GenBank U70136) expression. Loss of synovial fluid's (SF) lubricating

ability has been implicated in the pathogenesis of degenerative joint

disease. METHODS: A retrospective ED observational study from May 1,

1999, to October 1, 2000, of adult and pediatric patients presenting

with radiographically negative knee joint complaints and clinical

evidence of joint effusion. Knee joints were aspirated by the emergency

physician and the synovial fluid tested for lubricating ability and

collagen type II degeneration. Lubricating ability was assayed in vitro

in an arthrotripsometer oscillating latex apposed to polished glass

under a load of 0.35 106 N/m2. Results were reported as the coefficient

of friction ( micro ) relative to that of a 0.9% NaCl control; negative

deltamicro value indicates lubrication. Comparisons of deltamicro were

made to normal SF and aspirates from patients with osteoarthritis (OA)

and rheumatoid arthritis. Collagen type II fragments were measured by a

novel sandwich ELISA. RESULTS: Synovial fluid aliquots (n = 57)

lubricated poorly with deltamicro = -0.045 (95% confidence interval

= -0.006, -0.083) compared to normal SF with D micro = -0.095 (95% CI

= -0.088, -0.101). Only 20.6% of knee joint aspirates possessed normal

lubricating ability. An association exists between nucleated cell count

and deltamicro described by a logarithmic function. Collagen type II

fragments were present in aspirates at a concentration of 0.636

microg/ml (95% CI 0.495-0.777 microg/ml), significantly higher than

0.173 microg/ml (95% CI 0.154-0.193 microg/ml) in the OA comparison

group.

CONCLUSION: Knee joints with synovitis, commonly encountered in the ED,

are frequently nonlubricated bearings and display catabolism of collagen

type II. This may play a role in acute cartilage destruction ultimately

resulting in posttraumatic OA.

PMID: 14994405

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