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Topic:Synovial Fluid
Synovial fluid is a viscous, lubricating liquid found within the joint cavities of horses. It serves to reduce friction between the articular cartilage of synovial joints during movement. Composed primarily of hyaluronic acid and lubricin, synovial fluid also contains proteins, electrolytes, and cells. Its composition can change in response to joint disease or injury, making it a subject of interest in veterinary diagnostics. Analyzing synovial fluid can provide insights into joint health, inflammation, and the presence of infections. This page compiles peer-reviewed research studies and scholarly articles that explore the composition, function, and diagnostic applications of synovial fluid in equine medicine.
Single-cell sequencing reveals synovial fluid γδ T-cell expansion in equine experimental osteoarthritis. Define temporal cellular changes following joint injury using single-cell RNA sequencing in experimental equine posttraumatic osteoarthritis (PTOA). Unassigned: PTOA was induced in 4 Quarter Horses (3 to 5 years) via carpal osteochondral fragmentation and high-speed treadmill exercise. Synovial fluid (SF) cells and synovium were sampled over 18 weeks (November 2023 to April 2024). Single-cell suspensions were processed (10x Genomics Chromium iX), then aligned to the equine genome (Cell Ranger). Downstream analysis was completed in the R Seurat package. Differential gene expression (log2[fold c...
[Puncture wounds of the equine hoof – a retrospective study of 96 cases – Part 2: Management and prognosis]. Puncture wounds are a common and potentially life-threatening injury in equine veterinary practice. The aim of this study was to systematically analyze data from horses presenting to the clinic with a puncture wound. Unassigned: A retrospective study was conducted on patient data from horses with a puncture wound in the period from September 2008 to August 2024. Analyzed data included medical management and surgical treatment, complications, duration and costs of hospitalization, short-term survival rate and treatment success. Unassigned: A total of 96 horses met the inclusion criteria. Seven ...
Epidural 0.125% ropivacaine is safe but insufficient for induced tibiotarsal joint pain. Epidural injection of a low concentration of the local anaesthetic ropivacaine produces analgesia without neurological deficits or ileus in people. Objective: To determine if epidural 0.125% ropivacaine mitigates induced hindlimb lameness in horses while preserving neurological function and gastrointestinal (GI) motility. Methods: Randomised, blinded, controlled, crossover study. Methods: Eight healthy, sound horses underwent two treatments in random order, separated by at least 3 weeks: epidural saline or epidural ropivacaine. For each treatment, an epidural catheter was inserted at the fir...
Cord blood mesenchymal stromal cells combined with hyaluronic acid show symptom-modifying and potential disease-modifying effects in an equine osteoarthritis fetlock chip model. Osteoarthritis (OA) is a major cause of lameness in horses, and current therapies largely address clinical signs rather than disease progression. Mesenchymal stromal cells (MSCs) have shown promise as disease-modifying biologics, but their effects on joint structure and immunologic phenotype remain incompletely characterized. Unassigned: To evaluate the safety and efficacy of pooled cryopreserved equine umbilical cord blood-derived MSCs (eCB-MSCs) combined with hyaluronic acid (HA) for surgically induced fetlock OA in horses, using integrated clinical, imaging, and synovial biomarker outcomes....
Neosaxitoxin Downregulates Inflammation in an Equine In Vivo Model of Osteoarthritis. Chronic synovial inflammation is a hallmark of osteoarthritis progression and is tightly regulated by synovial macrophages. Recently, voltage-gated sodium channels (NaV) have emerged as potent modulators of macrophage-driven inflammation, positioning them as novel therapeutic targets. Among selective NaV channel blockers, neosaxitoxin exerts remarkable anesthetic and immunomodulatory effects; however, its effects on joint inflammation upon intra-articular delivery remain unexplored. Using an equine model of bilateral carpal osteoarthritis, this study evaluated the immunomodulatory and tissue-p...
Synovial fluid oxidative stress index as a biomarker for arthritis severity in thoroughbred racehorses. Arthritis is a major cause of lameness in racehorses. Even when lameness improves, it may recur after training resumes, making it difficult to determine the disease state and when to end treatment. This retrospective observational study examined whether oxidative stress in synovial fluid could assess arthritis status in racehorses. Synovial fluid samples obtained during routine clinical practice from horses with arthritis and control samples obtained from horses without clinical or radiographic evidence of carpal joint disease were retrospectively analyzed. A total of 72 Thoroughbreds in Japan...
Anti-Inflammatory and Metabolic Effects of Fresh Versus Freeze-Dried Platelet-Rich Plasma on Equine Osteoarthritis in an Ex Vivo Cartilage-Synovium Explant Co-Culture System: A Pilot Study. Equine osteoarthritis (OA) is a major cause of lameness and economic loss in horses. While platelet-rich plasma (PRP) has clinical potential, the biological effects of fresh PRP (F-PRP) and freeze-dried PRP (FD-PRP) remain insufficiently defined. This pilot study compared 25% and 50% F-PRP and FD-PRP in an interleukin-1β-induced equine cartilage-synovium explant co-culture model. PRP treatments reduced inflammatory responses, with significant downregulation of COX-2 and PGE2 expression, and 25% F-PRP showed the most consistent inhibition of nitric oxide production. PRP also significantly redu...
Correction: Phenylbutazone concentrations in synovial fluid following administration via intravenous regional limb perfusion in the forelimbs of six adult horses. [This corrects the article DOI: 10.3389/fmed.2026.1810077.].
Dental disorders are associated with minimal synovial changes in the temporomandibular joint in horses. Dental disorders have been proposed as factors contributing to temporomandibular joint (TMJ) discomfort in horses, but objective evidence linking these conditions to synovial fluid alterations remains limited. This study evaluated whether the severity of dental abnormalities influences the physicochemical and cytological characteristics of TMJ synovial fluid and whether occlusal adjustment induces measurable synovial changes over time. Unassigned: Thirty-three horses were assigned to mild, moderate, or severe dental abnormality groups. Synovial fluid was collected bilaterally from the discotem...
Intra-articular interleukin-1β induces early synovitis in an ex vivo autologously perfused equine forelimb model. To evaluate an ex vivo model of synovitis induced by IA lipopolysaccharide (LPS) and IL-1β in isolated, perfused equine forelimbs. Unassigned: Forelimbs and blood were collected from 12 clinically unremarkable horses following slaughter at a licensed abattoir. In 8 limbs, 2 of 3 phalangeal joints were injected with LPS (0.5 to 5 ng, 4 limbs) or IL-1β (100 ng, 4 limbs) diluted in 1 mL of distilled water. All limbs were perfused with autologous perfusate for 8 hours. Synovial fluid cytology and synovium sample histology scores for synovitis (0 = no changes and 3 = marked changes) were assessed...
Intra-articular 2.5% polyacrylamide hydrogel alters synovial immune pathways in equine experimental osteoarthritis. To determine differential gene expression in synovial tissues following injection of IA 2.5% polyacrylamide hydrogel (2.5% iPAAG), a biocompatible nondegradable synthetic polymer, to treat osteoarthritis (OA). Unassigned: Osteoarthritis was induced in 1 middle carpal joint of 16, 2- to 5-year-old horses (7 mares and 9 geldings) via surgical osteochondral fragment creation in combination with exercise on a high-speed treadmill; the contralateral limb underwent a sham operation. Horses were exercised 5 days per week, beginning on day 16 postoperatively. The osteochondral fragment joint was injec...
Synovial transcriptomic biomarkers predict structural severity in equine osteochondral fragment-induced experimental osteoarthritis. Develop a global joint score (GJS) reflecting equine osteoarthritis (OA) structural severity and identify clinical or molecular parameters predicting disease severity. Unassigned: A retrospective analysis was performed using data from horses (n = 104; 58 females and 46 geldings; 2 to 5 years old) undergoing experimental OA induction via surgical osteochondral fragment creation in the middle carpal joint and high-speed treadmill exercise over 70 days. Longitudinal measures included subjective lameness examinations (lameness, effusion, and flexion), synovial fluid (SF) and serum glycosaminoglyca...
Comparison of Magnetic Resonance Imaging and Computed Tomography for Evaluation of Cervical Vertebral Nerves and Synovial Tissues in Horses with Cervical Spinal Disease. Pathology of the cervical spine is an important cause of poor performance in sport horses. Computed tomography (CT) and magnetic resonance imaging (MRI) have improved musculoskeletal diagnostic capabilities. CT is well-suited to assess osseous pathology, although it is limited for assessing soft tissues. MRI, the gold standard for imaging soft tissues, cannot be used for antemortem imaging of the equine cervical spine. The diagnostic potential of CT for evaluating soft tissues of the equine cervical spine compared to MRI is not well-defined and warrants investigation. Postmortem MRI was perfor...
Pilot Study of an Alpha-2-Macroglobulin-Enriched Plasma-Derived Orthobiologic Preparation in Sport Horses with Chronic Degenerative Joint Disease. Chronic joint disease is a major cause of lameness and reduced performance in sport horses and is characterized by persistent synovial inflammation and protease-mediated matrix degradation. This exploratory prospective pilot study investigated clinical outcomes and synovial biomarker changes following intra-articular administration of an α-2-macroglobulin plasma-derived preparation. Twenty client-owned sport horses were observed in the treatment group (n = 10) or a comparison group (n = 10) and monitored for up to 180 days under field conditions. Clinical outcomes were assessed longitudinally...
Composition of allogeneic equine orthobiologics and their repeated intra-articular administrations. Orthobiologics such as platelet-rich plasma (PRP) and alpha-2-macroglobulin (A2MG) are increasingly used for equine musculoskeletal injuries. However, their composition and safety with repeated allogeneic intra-articular administration remain poorly investigated. Objective: To characterise orthobiological preparations with or without 1 h incubation at 37°C (PRP, PRP + Inc, A2MG, A2MG + Inc) and evaluate immunological safety following repeated intra-articular administration (autologous and allogeneic) of PRP combined with A2MG + Inc in healthy horses. Methods: In vivo experiments...
Immunohistological characterization of equine synovial tissue in metacarpophalangeal joints of different ages and osteoarthritis status. Synovial macrophages' role in equine osteoarthritis (OA) is not well understood, despite horses being a model for human degenerative joint disorders. Equine synovial macrophages' characterization is limited and age-related changes are not described. This study aimed to evaluate surface marker distribution and expression from potential synovial tissue macrophages in foals, adult non-affected, and OA-affected horses. Unassigned: Surface markers (CD14, CD16, CD206) were quantitatively evaluated on dorsal villous synovial biopsies from the metacarpophalangeal joint of foals (F), non-affected (cont...
CD8+ T-cells, CD86+ macrophages and TNF-α signalling pathways are correlated with fetlock osteoarthritis in racehorses. There is emerging evidence for the role of the immune system in osteoarthritis (OA) pathophysiology; however, little is known about how immune cells and the synovial transcriptome are altered in naturally occurring equine OA. Objective: To evaluate synovial fluid (SF) and synovial membrane (SM) immune cell populations and the SM transcriptome in racehorses with fetlock OA. Methods: Cross-sectional cadaver study. Methods: Fetlock joints from racehorses euthanised at NY racetracks were considered for inclusion. SF and SM were analysed by flow cytometry using T-cell (CD3, CD4, CD8) and macrophage...
Toll-like receptor 3-activated allogeneic umbilical cord blood-derived mesenchymal stromal cells as an adjunct for the treatment of synovial sepsis in 3 horses. To describe the case presentation, treatment, and outcome of horses treated with Toll-like receptor 3 (TLR-3)-activated allogeneic umbilical cord blood-derived mesenchymal stromal cells (CB-MSCs). Unassigned: 3 horses presenting with chronic or antimicrobial-resistant (AMR) septic synovitis. Unassigned: All horses presented with clinical signs associated with septic synovitis including marked grade 4/5 lameness, joint effusion, heat/swelling of the limb, and synovial fluid parameters consistent with sepsis. Case 1 presented 3 weeks following the onset of clinical signs. Cases 2 and 3 developed...
A single pneumatic tourniquet is superior to wide rubber tourniquets for saphenous intravenous regional limb perfusion with amikacin in standing, sedated horses. To establish whether tourniquet type and number influence synovial fluid amikacin concentrations of the tarsocrural joint (TCJ) or metatarsophalangeal joint (MTPJ) after standing saphenous IV regional limb perfusion (IVRLP) with 2 g of amikacin. Unassigned: 8 healthy adult horses underwent 4 saphenous IVRLP protocols with amikacin, differing in tourniquet type (pneumatic vs wide rubber) and number (1 placed mid-gaskin vs 1 placed mid-gaskin and 1 mid-metatarsus) in a randomized, crossover design. Amikacin concentrations were measured in serum and synovial fluid of the TCJ and MTPJ at 15 and 30...
[Puncture wounds of the equine hoof – a retrospective study of 96 cases – Part 1: Prevalence, clinical findings and diagnostic investigations]. Penetrating wounds of the hoof are common and potentially life-threatening injuries in equine veterinary practice. The aim of this study was the systematic data analysis of horses presenting to the clinic with a solar puncture wound.In this retrospective study, patient data from horses presented with a puncture wound to the hoof in the period from September 2008 to August 2024 were collected. The analyzed data covered signalment, intended use, and insurance status. The following were also considered: previous history including the period between injury and presentation to the clinic, affected ...
Mass culture of equine synovial fluid-derived mesenchymal stromal cells using nonwoven polyethylene terephthalate fabrics. Culture protocols need to yield 100 million equine synovial fluid (SF)-derived mesenchymal stromal cells (SF-MSCs) in around 3 weeks are needed, before these cells can be evaluated as agents of articular repair in clinical trials. Objective: To investigate mass culture of equine SF-MSC culture protocols using nonwoven polyethylene terephthalate (PET) fabrics for the potential to meet the targets for clinical trials. Methods: In vitro experiments. Methods: SF samples were collected from the carpal joints in thoroughbred racehorses (n = 21) undergoing arthroscopic surgery and cultured in 10%...
Intra-articular hydrogel therapeutics exhibit anti-inflammatory effects on cytokine-stimulated equine cartilage and synovial membrane explants. To investigate whether IA hydrogel therapeutics alter the inflammatory and/or degradative responses of articular cartilage (AC) and synovial membrane (SM) to cytokine stimulation. Unassigned: AC and SM tissue explants were stimulated with interleukin-1β (IL-1β) or tumor necrosis factor-α (TNF-α) and simultaneously treated with triamcinolone acetonide, hyaluronic acid, collagen-elastin hydrogel microparticles (CEHM), or 2.5% polyacrylamide hydrogel (2.5% iPAAG) at 3 doses. Synovial membrane (n = 9 explants, 3 horses) was stimulated/treated for 18 hours, whereas AC (12 explants, 6 horses) wa...
Postmortem characterization of cranial nuchal bursa and ligament in healthy horses reveals subclinical gross and histopathologic abnormalities. To investigate the presence of subclinical cranial nuchal bursitis and characterize its histopathologic features and association with Borrelia burgdorferi. Unassigned: This was a prospective descriptive cadaver study on a convenience population of horses in a B burgdorferi-endemic region (15 horses: 5 geldings and 10 mares of various breeds; 4 to 29 years old). Horses without history or clinical signs of cranial nuchal bursitis underwent euthanasia and tissue donation. Cranial nuchal bursa, synovial fluid, and nuchal ligament were collected postmortem. The bursa and ligament were evaluated via...
Computer-Aided Diagnosis of Equine Temporomandibular Joint Osteoarthritis Using Machine Learning Integrating Computed Tomography Findings and Synovial Fluid Biomarkers. Horses presenting with temporomandibular joint (TMJ) dysfunctions are often clinically evaluated for TMJ osteoarthritis (OA). Due to the unique characteristic of TMJ-related pain, the clinical diagnosis of equine TMJ OA is challenging; however, it may be supported by computer-aided tools incorporating biomarker data. This study aims to evaluate a machine learning-based approach to address a binary classification distinguishing healthy TMJs from TMJ OA. Among 50 equine cadaver heads, 82 TMJs were included and annotated as healthy or OA based on histological and computed tomography (CT) findings...
Septic arthritis caused by Streptococcus equi subspecies zooepidemicus: a case report. subspecies (SESZ) is an uncommon zoonotic pathogen in humans but can cause severe joint infections. Reported cases are often linked to exposure to horses, dairy products, or raw pork, though infections may occur without an identifiable animal source. Unassigned: An 84-year-old man with multiple comorbidities presented with acute left shoulder pain, fever, and chills. Synovial fluid aspiration yielded turbid fluid containing calcium pyrophosphate dihydrate crystals, while Gram stain was negative. Despite empiric broad-spectrum antibiotics, his symptoms persisted, requiring surgical irrigation...
Ertapenem Pharmacokinetics in Equine Plasma and Synovial Fluid Following a Single Intravenous Dose. This study describes the pharmacokinetics of ertapenem, a carbapenem antimicrobial that has not been previously studied in equids. Administered as a 30 mg/kg intravenous bolus to six healthy horses, serial blood and synovial samples were obtained over 8 h after administration. Pharmacokinetic analysis of plasma and synovial fluid was performed. In plasma, the AUC was 353.10 h × μg/mL (CV = 49.02%), Vss 79.34 mL/kg (CV = 22.85%), CL 84.96 mL/h/kg (CV = 31.31%) and t1/2 2.03 h (CV = 15.32%). In synovial fluid, the AUC was 524.10 h × μg/mL (CV = 16.03...
Three-Dimensional Reconstruction of the Equine Palmar Metacarpal Region Using E12 Plastinated Sections. Digital technologies have improved the visualization of anatomical structures for veterinary education and clinical practice. In this study, a detailed three-dimensional anatomical model of the equine palmar metacarpal region was generated using E12-based epoxy sheet plastination combined with digital reconstruction in Amira V5.6 software. Serial cross-sections of the metacarpal region provided high-resolution visualization of bones, tendons, ligaments, nerves, vessels, fasciae, and synovial structures, with minimal shrinkage or deformation, ensuring improved anatomical accuracy. These section...
Ultrasonographic Evidence of Synovitis Correlates with Synovial Citrate and TBARS in Equine Osteoarthritis. Osteoarthritis (OA) is a degenerative joint disease that affects humans and animals worldwide. Its early diagnosis remains challenging due to subtle clinical signs and late radiographic changes. This study aimed to explore candidate biomarkers associated with spontaneous OA and to investigate their correlation with ultrasonographic scores to support early diagnosis. Clinical, radiographic, and ultrasonographic evaluations were performed on 52 equine metacarpophalangeal joints, with and without OA, allowing joint scoring and classification into osteoarthritis (OAG) and control groups. Synovial ...
Senescence-associated gene pathways are differentially expressed in equine aging-related osteoarthritis. Osteoarthritis (OA) is a aging-associated degenerative joint disease. The objective was to determine relative senescence gene expression in joints and leukocytes of OA horses toward considering senotherapeutics to manage OA. Unassigned: To define local (joint) and systemic (peripheral blood mononuclear cells [PBMCs]) senescence burden, synovial fluid cell single-cell RNA sequencing and PBMC mRNA sequencing datasets (n = 65 samples) were examined. Differential analyses were conducted using limma to compare OA versus control. A custom 3,043-gene senescence set curated from published metadata was...
The effect of arthroscopic lavage volume on bacterial culture of egress fluid in horses with experimentally induced septic arthritis and synovitis. To evaluate if high-volume lavage results in a negative bacterial culture of egress fluid, regardless of pathogen in an experimental model of equine septic arthritis. Methods: Experimental study. Methods: A total of 11 horses in three groups (lipopolysaccharide [LPS] Group 1, n = 4; Escherichia coli [E. coli] Group 2, n = 4; Staphylococcus aureus [S. aureus] Group 3, n = 3). Methods: A middle carpal joint of each horse was injected with LPS (synovitis Group 1), E. coli (septic arthritis Group 2) or S. aureus (septic arthritis Group 3). Arthroscopic lavage of the middle carpal joint...
