Intra-articular (IA) hyaluronic acid (HA) is commonly used to treat equine arthritis. Inflammatory response or "joint flare" is a recognized potential side effect. However, the incidence and severity of inflammation following IA HA injection in horses is not well documented. This study compared the effects of two IA HA formulations of different molecular weight (MW) and a saline control on clinical signs and synovial fluid markers of inflammation in normal equine joints. Eight adult horses each had three healthy fetlock joints randomly assigned to treatment with either 1.4 mega Dalton HA, 0.8 mega Dalton HA or saline control once weekly for three weeks. Clinical evaluation and synovial fluid analysis were performed by blinded assessors. Outcomes of interest were lameness score, joint effusion score and synovial fluid white cell count and differential, total protein, viscosity and serum amyloid A. Joints injected with HA developed significant mild-to-moderate inflammatory responses often associated with lameness and joint effusion compared with saline control joints. The higher MW HA formulation elicited a significantly greater inflammatory response than the lower MW HA after the first injection. In HA injected joints, viscosity remained poor for the entire study. Both IA HA formulations in this study induced an inflammatory response in healthy equine joints. This may have implications for the use of HA in equine joints. The findings in this study are limited to the two HA formulations used. Further investigation of different HA formulations and the use of HA in normal and arthritic equine joints is warranted.

中文翻译：

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评价正常马关节中对两种关节内透明质酸制剂的炎症反应。

关节内（IA）透明质酸（HA）通常用于治疗马关节炎。炎症反应或“关节耀斑”是公认的潜在副作用。然而，没有充分记录马注射IA HA后炎症的发生率和严重性。这项研究比较了两种不同分子量（MW）的IA HA制剂和盐水对照对正常马关节炎症的临床体征和滑液标志物的影响。八只成年马每只都有三个健康的节肢关节，每周一次随机分配接受1.4兆道尔顿HA，0.8兆道尔顿HA或生理盐水对照的治疗，持续3周。由盲人评估者进行临床评估和滑液分析。感兴趣的结果是la行评分，关节积液评分和滑液白细胞计数及差异，总蛋白，粘度和血清淀粉样蛋白A。与生理盐水对照关节相比，注射HA的关节出现明显的轻度至中度炎症反应，通常与la行和关节积液有关。第一次注射后，较高的MW HA制剂比较低的MW HA引起更大的炎症反应。在HA注射的关节中，整个研究期间的粘度仍然很差。这项研究中的两种IA HA制剂均在健康的马关节中引起炎症反应。这可能对在马关节中使用HA产生影响。这项研究的发现仅限于所用的两种HA制剂。有必要进一步研究不同的HA配方，以及在正常和关节炎马关节中使用HA的方法。