Soft Tissue Knee Injury With Concomitant Osteochondral Fracture Is Associated With Higher Degree of Acute Joint Inflammation

Abstract

Background: Osteochondral fractures are often seen on magnetic resonance imaging (MRI) of acutely injured knees, but their existence has gained little interest because of a lack of knowledge of their relation to treatment options and outcome. It is not clear whether acute phase synovial fluid (SF) concentrations of cartilage and bone markers and proinflammatory cytokines are different between traumatically injured knees with or without osteochondral fracture. Hypothesis: Acutely injured knees with an osteochondral fracture, particularly fractures with disrupted cortical bone, have higher concentrations of bone markers and cytokines than do knees without an osteochondral fracture. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Synovial fluid (hemarthrosis) was aspirated (median 1 day after injury) and 1.5-T MRI was performed (median 8 days after injury) in the acutely injured knee of 98 individuals (26% women; mean age, 23 years). As visualized on MRI, 39% knees had an osteochondral fracture with disrupted cortical bone, 30% had an osteochondral fracture with intact cortical bone, and 32% did not have an osteochondral fracture. Concentrations of sulfated glycosaminoglycan, ARGS aggrecan, cartilage oligomeric matrix protein, osteocalcin, secreted protein acidic and rich in cysteine (SPARC), osteopontin and proinflammatory cytokines (interleukin [IL]–1β, IL-6, IL-8, and tumor necrosis factor [TNF]–α) were analyzed. Results: After adjusting for days between injury and SF aspiration, age at injury, and sex, knees with any osteochondral fracture (with or without disrupted cortical bone) had significantly higher SF concentrations of TNF-α (median [interquartile range (IQR)] = 9 [7-12] pg/mL vs 7 [5-14] pg/mL; P = .013), whereas knees with an osteochondral fracture with disrupted cortical bone had significantly higher SF concentrations (medians [IQRs]) of SPARC (492 [328-754] ng/mL vs 407 [140-685] ng/mL; P = .030), IL-8 (278 [148-628] pg/mL vs 138 [67-413] pg/mL; P = .028), and TNF-α (11 [7-15] pg/mL vs 7 [5-14] pg/mL; P = .004) compared with knees without an osteochondral fracture. Conclusion: In acutely injured knees with hemarthrosis, a concomitant osteochondral fracture with disrupted cortical bone is associated with a higher degree of joint inflammation.