Which is the more effective intra-articular therapy: HA or steroids?

It has been proposed that hyaluronic acid (HA) imparts viscosity to synovial fluid and exerts an anti-inflammatory effect [1]. Hyaluronic acid was the most commonly selected medication mixed with a corticosteroid in 59.4% of 831 respondents in a cross-sectional survey of the American Association of Equine Practitioners [2].
It has been suggested that the mode of action of HA depends on molecular weight but there is no indication that molecular weight has clinical relevance [3]. A prospective, randomised, double-blind, placebo-controlled clinical trial to evaluate the efficacy of intra-articular HA for osteoarthritis (OA) of the human knee found HA was more effective than the placebo in reducing the signs of OA but no difference was seen in treatments lasting 3 weeks compared to treatments lasting 6 weeks [4]; this study was limited by the absence of a control group.
Triamcinolone significantly increased the mean white blood cell (WBC) count in synovial fluid but also reduced lameness, oedema and the mean total protein concentration when compared to the control when injected into metacarpophalangeal (MCP) joints of horses with experimentally induced acute synovitis [5]. In vitro, methylprednisolone (MPA) decreased production of proteoglycan by equine chondrocytes [6] and, in a cartilage explant study, addition of HA failed to mitigate this deleterious effect [7]. In an interleukin-1 (IL-1)-induced inflammation model on equine articular cartilage pellets, MPA in combination with HA increased total pellet glucosaminoglycan (GAG) and new proteoglycan (PG) synthesis compared with the IL-1–treated controls [8]. Using the same model high concentrations of HA or triamcinolone alone, or in combination, ameliorated the effects of IL-1 induced GAG catabolism of equine chondrocytes [9]. This was supported by an equine cartilage explant study which found that triamcinolone or HA decreased empty lacunae following lipopolysaccharide (LPS) challenge [10]. […]