Joint Disease In Horses Research Articles

Infrared Spectroscopy of Synovial Fluid Shows Accuracy as an Early Biomarker in an Equine Model of Traumatic Osteoarthritis.

Osteoarthritis is a leading cause of lameness and joint disease in horses. A simple, economical, and accurate diagnostic test is required for routine screening for OA. This study aimed to evaluate infrared (IR)-based synovial fluid biomarker profiling to detect early changes associated with a traumatically induced model of equine carpal osteoarthritis (OA). Unilateral carpal OA was induced arthroscopically in 9 of 17 healthy thoroughbred fillies; the remainder served as Sham-operated controls. The median age of both groups was 2 years. Synovial fluid (SF) was obtained before surgical induction of OA (Day 0) and weekly until Day 63. IR absorbance spectra were acquired from dried SF films. Following spectral pre-processing, predictive models using random forests were used to differentiate OA, Sham, and Control samples. The accuracy for distinguishing between OA and any other joint group was 80%. The classification accuracy by sampling day was 87%. For paired classification tasks, the accuracies by joint were 75% for OA vs. OA Control and 70% for OA vs. Sham. The accuracy for separating horses by group (OA vs. Sham) was 68%. In conclusion, SF IR spectroscopy accurately discriminates traumatically induced OA joints from controls.

Analysis of the prevalence of osteoarticular pathologies in horses based on the results of radiography

This article provides an overview of the literatureand recent scientific research on the spread of bone andjoint pathology among horses. Reasoned relevance andprospects of research on this issue.The article also presents the results of own research aimed at analyzing the distribution of bone andjoint diseases in horses on the territory of equestriansports clubs of Kharkiv region, Poltava region andKyiv region with the aim of finding out the frequencyof occurrence of this group of pathologies.To achievethe goal, radiography of 40 heads of horses aged 8-21years of riding breeds, which had signs of lamenessof the resisting limb, was carried out. Based on theresults of the research, differential diagnosis of boneand joint diseases was carried out. Differential diagnosis of arthrosis was presented taking into account thepathological process and its localization. According tothe obtained data, arthrosis accounted for 55% of thetotal number of studied animals, osteoporosis – 25%,periostitis – 7.5%, cystic formations and bone cracks –7.5%. Bone and joint pathology was not detected in theremaining 5%. Arthritic phenomena were localized inthe joints of the distal part of the limbs, namely: hoof,coronal, putative, carpal and hock. A case was registered when the degenerative process was concentratednot only in one joint, but also moved to the lower one.Among 55% of arthrosis, there were cases of osteoarthrosis, exfoliative osteochondritis, presence of ossification within the joint. The article also comparesown results with data obtained by foreign researchersregarding the distribution of bone and joint pathologiesin horses.In addition, the article substantiates the feasibilityof analyzing the spread of bone and joint diseases inhorses and demonstrates the effectiveness of X-ray diagnostics of these pathologies. Key words: arthrosis, periostitis, osteoporosis, osteoarthritis, osteoarthritis of the hock joint, osteochondritis dissecans, ossification.

Ultrasonography of the Metacarpal/Tarsal-Phalangeal Joints in Healthy Racehorses: Normal Appearance, Breed-Related and Age-Related Features.

Simple SummaryThe ultrasound appearance of cartilage thickness and subchondral bone changes according to the age of the horse and the health status of the joints. Specific ultrasound features have been described in different joint diseases in horses. Knowledge of the normal features is thus essential during clinical investigations. The present research evaluates the ultrasound features of metacarpal/tarsal-phalangeal joints in healthy racehorses, according to the age and breed. Twenty-eight racehorses (standardbreds and thoroughbreds) were enrolled and grouped according to age (<5 and ≥5 years old). Fetlock cartilage appearance, thickness and subchondral bone appearance were ultrasonographically assessed. In younger compared to older standardbreds, the cartilage appeared thinner and with a normal ultrasound appearance, which suggests the use of specific references for the ultrasound features of the fetlock.In adult horses, specific ultrasound (US) features and reference values have been reported for the appearance of the joint cartilage and thickness according to the type of joint, such as femoropatellar and tarsocrural. The US appearance of the fetlock has been described in several diseases. The present research evaluates the US features of the metacarpal/tarsal-phalangeal joints in healthy racehorses according to age and breed, since no information is available in the literature. Seventy-one fetlocks in 28 healthy horses (15/28 thoroughbreds and 13/28 standardbreds) were assessed. The horses were grouped as follows: group A < 5 years old vs. group B ≥ 5. A portable ultrasound machine and a linear transducer (5–7.5 MHz) were used. Dorsal metacarpal/tarsal-phalangeal joints were scanned. The US images were reviewed offline in terms of articular cartilage appearance, thickness, and subchondral bone appearance by an experienced observer. Data were reported as the median, minimum, and maximum for cartilage thickness values, and differences between groups were evaluated. Cartilage thickness values were statistically lower in group A than B in the standardbreds, except for the lateral thickness in longitudinal view. No differences were detected in the thoroughbreds within age groups. All of the young standardbreds showed a normal cartilage and subchondral appearance. No statistical differences were found between breeds. Our results highlight the characteristics of the US appearance of metacarpal/tarsal-phalangeal joints specifically in racehorses, with some variations according to age. Since the cartilage can change according to joint growth, age and training activity, the present findings suggest the use of specific references for US features, which are key to correctly evaluating the health of the fetlock.

Etiology, frequency and clinical signs of aseptic jumping joint inflammation in horses

Articular pathologies in horses participating in sports and kupkari are recorded mainly at the end of the autumn season, in winter and spring, in the republic's farms out of 466 horse heads, 44 heads (9.4%) had various aseptic inflammations, for example, 8 animals have acute synovitis, 21 horses have chronic synovitis and 15 animals have periarticular fibrositis, traumatic injuries are considered the main cause of joint disease in horses participating in the Kupkari. Under the influence of the above etiological factors, degenerative changes in cells and tissues are observed, as a result of which the necessary processes in the body are disrupted and, as a result, the protective properties of the body are reduced. The animal felt pain during passive movement, and low to moderate chromate levels were observed during movement. When you press your finger on one of the tubercles of the joint, the movement of fluid towards the second tubercle is clearly felt. In animals with periarticular fibrosis, the fibrous capsule increases, the ligaments thicken, and their elasticity decreases. At the onset of the disease, pain was observed on palpation of the joint capsule and ligaments, at rest no pain was observed, but severe lameness was observed during movement, work.

Nanoparticles from Equine Fetal Bone Marrow-Derived Cells Enhance the Survival of Injured Chondrocytes.

Simple SummaryReports on the potential of using mesenchymal stem cells (MSCs) for treating equine degenerative joint diseases have been increasing over the past few years, in spite of limitations such as uncontrolled differentiation, immunogenicity, and tumorigenicity. We elucidated an allogenic alternative, where equine bone marrow-derived cells (BMC)-derived nanoparticles (BMC-NPs) can be used to promote the growth of chondrocytes, and simultaneously reduce their cytokine-induced apoptosis. The role of BMC-NPs in activation of signaling pathway molecules was also established.Recent studies have shown that mesenchymal stem cells (MSCs) can play a restorative role against degenerative joint diseases in horses. The purpose of this study was to investigate whether fetal bone marrow-derived cells (BMC)-derived nanoparticles (BMC-NPs) can stimulate the survival of equine chondrocytes. Equine fetal BMCs were isolated and characterized, and the role of BMC-NPs s in equine chondrocytes undergoing inflammatory cell death was examined. BMCs have several characteristics, such as the potential to differentiate into chondrocytes and osteocytes. Additionally, BMCs expressed immunoregulatory genes in response to treatment with tumor necrosis factor-alpha (TNF-α) and Interleukin 1 beta (IL-1β). We found that BMC-NPs were taken up by equine chondrocytes. Functionally, BMC-NPs promoted the growth of chondrocytes, and reduced apoptosis induced by inflammatory cytokines. Furthermore, we observed that BMC-NPs upregulated the phosphorylation of protein kinase B (Akt) in the presence of IL-1β, and reduced the phosphorylation of TNF-α-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) in the chondrocytes. Cumulatively, our study demonstrated that equine fetal BMC-NPs have the potential to stimulate the survival of chondrocytes damaged by inflammatory cytokines. Thus, BMC-NPs may become an alternative cell-free allogenic therapeutic for degenerative joint diseases in horses.

Ultrasonographic Appearance of Elbow Joints in a Population of Amiata Donkeys

Ultrasound (US) is a well-established technique for investigating joint diseases in horses, complementary to radiography. Few studies have been performed on the ultrasonographic aspect of the elbow joint in horses and no reports are available on donkeys. The aim of this study is to describe the ultrasonographic appearance of the elbow joint in healthy donkeys. Descriptive cohort study included 34 elbow joints, which were evaluated in 17 donkeys. Inclusion criteria included no lameness or musculoskeletal diseases in the donkeys. The structures evaluated were the lateral and medial collateral ligaments, ulnaris lateralis proximal tendon, distal biceps brachii tendon, triceps brachii tendon, and the articular space. For each structure, one good-quality image was recorded. The structures were retrospectively assessed for echogenicity, fiber orientation, bone appearance, and shape. The prevalence of the visualized structures was calculated. Cohen κ coefficient was calculated for the repeatability (intraoperator agreement), the reproducibility (interoperator agreement), and the influence of the operator’s experience in US examination. The US appearance of the structures was described. Statistical analysis showed scarce-to-moderate agreement concerning the repeatability and mostly scarce-to-good agreement concerning the reproducibility of the US examination; finally, low-to-discrete agreement concerning the operator’s experience. Technical difficulties precluded an accurate description of the medial collateral ligament. The healthy animals included were limited. The US examination of the elbow joint in donkeys were similar to the features reported in horses. Individual experience partially influences the execution and the assessment of the US images.

Pressuring of Acupoints as a Complement to the Diagnosis of Stifle Diseases in Horses

Diseases of the stifle joint remain a challenge for veterinarians. The objective of this study was to achieve a valuable acupuncture suggestive diagnosis to be considered for stifle joint diseases in horses. Thirty-nine nonlame horses involved in different activities were assessed. Acupuncture was independently performed by two evaluators. Reactions of the animal when pressurizing the point suggestive of stifle disease (PSSD), Bladder-20 and/or Bladder-21, were considered as the inclusion criteria for inclusion in the stifle group (SG, n = 31), and the animals with no reactions were assigned to the control group (n = 8). Radiographic and ultrasonographic examinations were performed and evaluated by two independent professionals blinded to the group allocation. Thermographic examination of the PSSD and stifles was also performed, after acclimatization. The ultrasound scores and radiographic findings were higher in the SG than in the control group. Thermography evidenced increased temperature in the PSSD and stifles in the SG. The minimum acupuncture diagnostic criteria for stifle joint disease had a sensitivity of 87.5% and a specificity of 57.0%, and the addition of the acupoints Gallbladder–dorsal tuber coxae, Gallbladder-27, and Spleen-13 to the minimum diagnostic criteria improved sensitivity and specificity. In conclusion, assessing the reaction at the demonstrated acupoints can facilitate a diagnosis of a potential stifle lesion.

Equine Allogeneic Chondrogenic Induced Mesenchymal Stem Cells Are an Effective Treatment for Degenerative Joint Disease in Horses.

Degenerative joint disease is one of the main causes of equine early retirement from pleasure riding or a performance career. The disease is initially triggered by an abnormal loading of normal cartilage or a normal loading of abnormal cartilage. This primary insult is accompanied with joint inflammation, which leads to further progressive degeneration of the articular cartilage and changes in the surrounding tissues. Therefore, in search for an effective treatment, 75 adult horses with early signs of degenerative fetlock joint disease were enrolled in a randomized, multicenter, double-blinded, and placebo-controlled study. Fifty animals were injected intra-articularly with the investigational veterinary product (IVP) consisting of allogeneic chondrogenic induced mesenchymal stem cells (ciMSCs) with equine allogeneic plasma, and 25 horses were injected with 0.9% NaCl (saline) control product. From week 3 to 18 after treatment, lameness scores (P < 0.001), flexion test responses (P < 0.034), and joint effusion scores (P < 0.001) were remarkably superior in IVP-treated horses. Besides nasal discharge in both treatment groups, no adverse events were observed during the entire study period. On long-term follow-up (1 year), significantly more investigational product-treated horses were working at training level or were returned to their previous level of work (P < 0.001).

Joint disease in horses found to be more common than previously thought

Joint disease in horses found to be more common than previously thought

Evaluation of standing low-field magnetic resonance imaging for diagnosis of advanced distal interphalangeal primary degenerative joint disease in horses: 12 cases (2010-2014).

OBJECTIVE To report history, findings from clinical examinations and diagnostic imaging, treatment, and outcomes associated with distal interphalangeal primary degenerative joint disease (DIP-PDJD) and to evaluate diagnostic usefulness and limitations of standing low-field MRI, relative to radiography and ultrasonography, for the diagnosis of DIP-PDJD in horses. DESIGN Retrospective case series with nested evaluation study. ANIMALS 12 client-owned horses. PROCEDURES Medical records were reviewed, and data were collected regarding signalment, history, results of physical and diagnostic imaging examinations, treatments, and outcomes of horses that underwent radiography, ultrasonography, and standing MRI for DIP-PDJD. Findings from radiography, ultrasonography, and MRI were recorded, and abnormal findings were graded. The diagnostic usefulness of MRI, relative to radiography and ultrasonography, in the diagnosis of DIP-PDJD in horses was evaluated. RESULTS A diagnosis of DIP-PDJD was established in 12 of 176 (6.8%) horses that underwent MRI examination of a foot for locomotor disorders. Radiography and ultrasonography enabled confirmation of DIP-PDJD in 3 of the 12 horses, and standing MRI enabled confirmation of DIP-PDJD in the remaining 9. Mean grade for thinning joint space and cartilage were significantly greater when determined with MRI, compared with radiography. Mean grade for osteophytes and periarticular bone remodeling were significantly greater when determined with radiography and ultrasonography, compared with MRI. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that DIP-PDJD can be challenging to detect with routine imaging, especially when synovial effusion and periarticular new bone formation are absent. Standing low-field MRI represents a potentially useful diagnostic tool to diagnose advanced DIP-PDJD in horses.

Management of joint disease in horses

Russell Parker BVSc. MSc. DECVS. MRCVS, Liphook Equine Hospital, discusses the options

Plasma firocoxib concentrations after intra-articular injection of autologous conditioned serum prepared from firocoxib positive horses

Orthobiologics such as autologous conditioned serum (ACS) are often used to treat joint disease in horses. Because ACS is generated from the horse’s own blood, any medication administered at the time of preparation would likely be present in stored ACS, which could lead to an inadvertent positive drug test following intra-articular (IA) injection. The main objective of this study was to determine if ACS prepared from firocoxib positive horses could result in detectable plasma concentrations of the drug following IA injection. Firocoxib was administered to six horses at 0.1mg/kg PO twice at a 24h interval. Blood was obtained at 4h following the second dose and transferred to a separate syringe (Arthrex IRAP II) for ACS preparation. Plasma and ACS concentrations of firocoxib were analysed by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS). When horses were confirmed firocoxib negative, 7.5mL of ACS was injected into both tarsocrural joints. Blood samples were collected at 0, 4, 8, 12, 24, and 48h, and firocoxib concentration was measured.Mean (±standard error of the mean, SEM) plasma concentration of firocoxib 4h following the second dose was 33.3±4.72ng/mL. Mean (±SEM) firocoxib concentration in ACS was 35.4±4.47ng/mL. Fourteen days following the second and last dose of firocoxib, mean plasma concentration was below the lower limit of detection (LOD=1ng/mL) in all horses. Following IA injection of ACS, plasma concentrations of firocoxib remained below LOD at all times in all horses. ACS generated from horses with therapeutic plasma concentrations of firocoxib did not contain sufficient firocoxib to lead to a positive plasma drug test following IA administration.

Vital structures

Concluding his series on the nature of joint disease in horses, Dr Colin Roberts, equine veterinary consultant, University of Cambridge, discusses osteochondrosis

Changes in concentrations of haemostatic and inflammatory biomarkers in synovial fluid after intra-articular injection of lipopolysaccharide in horses

BackgroundSeptic arthritis is a common and potentially devastating disease characterized by severe intra-articular (IA) inflammation and fibrin deposition. Research into equine joint pathologies has focused on inflammation, but recent research in humans suggests that both haemostatic and inflammatory pathways are activated in the joint compartment in arthritic conditions. The aim of this study was to characterize the IA haemostatic and inflammatory responses in horses with experimental lipopolysaccharide (LPS)-induced joint inflammation. Inflammation was induced by IA injection of LPS into one antebrachiocarpal joint of six horses. Horses were evaluated clinically with subjective grading of lameness, and blood and synovial fluid (SF) samples were collected at post injection hours (PIH) -120, −96, −24, 0, 2, 4, 8, 16, 24, 36, 48, 72 and 144. Total protein (TP), white blood cell counts (WBC), serum amyloid A (SAA), haptoglobin, iron, fibrinogen, thrombin-antithrombin (TAT) and d-dimer concentrations were assessed in blood and SF.ResultsIntra-articular injection of LPS caused local and systemic signs of inflammation including increased rectal temperature, lameness and increased joint circumference and skin temperature. Most of the biomarkers (TP, WBC, haptoglobin, fibrinogen and TAT) measured in SF increased quickly after LPS injection (at PIH 2–4), whereas SAA and d-dimer levels increased more slowly (at PIH 16 and 144, respectively). SF iron concentrations did not change statistically significantly. Blood WBC, SAA, haptoglobin and fibrinogen increased and iron decreased significantly in response to the IA LPS injection, while TAT and d-dimer concentrations did not change. Repeated pre-injection arthrocenteses caused significant changes in SF concentrations of TP, WBC and haptoglobin.ConclusionSimilar to inflammatory joint disease in humans, joint inflammation in horses was accompanied by an IA haemostatic response with changes in fibrinogen, TAT and d-dimer concentrations. Inflammatory and haemostatic responses were induced simultaneously and may likely interact. Further studies of interactions between the two responses are needed for a better understanding of pathogenesis of joint disease in horses. Knowledge of effects of repeated arthrocenteses on levels of SF biomarkers may be of value when markers are used for diagnostic purposes.

Management of joint diseases in horses: Current and future prospects

Management of joint diseases in horses: Current and future prospects

Osteochondral dysplasia of the coxofemoral joints in a Friesian foal: Clinical findings and methods of diagnosis

SummaryDiseases of the coxofemoral (hip) joint are infrequently diagnosed in horses. Most cases are presented as an unilateral condition and usually are of traumatic origin. This case report describes a Friesian foal with a clinically obvious thoracolumbar kyphosis, combined with a weight‐shifting stance and a shortened stride of both hindlimbs. General clinical and lameness examinations, computed tomographic examination of the pelvis, and macroscopic and histopathological examinations of the coxofemoral joints were performed. This revealed a final, phenotypical diagnosis of a primary osteochondral dysplasia of both coxofemoral joints with secondary osteoarthritis. Similar to the occurrence of this condition in other species and considering the small genetic basis of the Friesian horse breed, a genetic predisposing factor is suspected to play a key role in the developing mechanism of dysplastic coxofemoral joint disease in horses as illustrated with this case. Computed tomography scanning appears to be a useful imaging technique in the detection of coxofemoral joint disease in small horses and foals.

Application of stem cells for the treatment of joint disease in horses.

Stem cells in the form of mesenchymal stromal cells derived from various sources have been identified to have the potential of supporting the therapy of joint disease in the horse, and preliminary data has been published about the clinical application of stem cells in horses suffering from clinical joint disease. Furthermore, the horse is recognized to be the ideal large animal model for the preclinical study of cell therapy in joints. The advantage of this species in this respect is the size of the joints, which makes surgical applications practically feasible in analogy to human surgery. Additionally, the horse is the only model species with a cartilage thickness in the knee joint comparable to that of humans. Especially the fact that horses develop clinical joint disease discerns this species from other large animal models like small ruminants. The therapy of clinical disease in model animal species represents the ideal situation for preclinical studies of novel therapeutic strategies. Here, we describe the experimental and clinical approaches to joint disease in the horse.

Synovial fluid growth factor and cytokine concentrations after intra-articular injection of a platelet-rich product in horses

Platelet-rich plasma (PRP) products may be useful for treatment of joint disease in horses, but may contain undesirable pro-inflammatory cytokines in addition to growth factors. This study investigated whether autologous PRP increases synovial fluid growth factor and cytokine concentrations when injected into normal equine metacarpophalangeal and metatarsophalangeal (fetlock) joints. Fetlock joints of seven healthy horses received one of four treatments: saline, resting PRP, CaCl2-activated PRP or thrombin-activated PRP. Synovial fluid was sampled prior to injection and at 6, 24, 48 and 96h post-injection. Platelet-derived growth factor (PDGF-BB), transforming growth factor β1 (TGFβ1), interleukin (IL)-6 and tumor necrosis factor α (TNFα) concentrations in synovial fluid and PRP were measured by ELISA. Synovial fluid PDGF-BB, TGFβ1, IL-6, TNFα and IL-1 concentrations were also measured in vitro after incubation for 6h with resting PRP only. Growth factor concentrations, but not cytokine concentrations, were significantly higher in activated PRP than in resting PRP samples. After intra-articular injection with resting or thrombin-activated PRP, synovial TGFβ1 increased significantly compared to baseline levels. TNFα and IL-6 were significantly increased in synovial fluid after thrombin-activated PRP injection. In vitro, growth factor concentrations increased significantly in synovial fluid after mixing with PRP, indicating that exogenous activation of PRP for intra-articular injection may be unnecessary, whereas cytokine levels did not. In conclusion, thrombin-activated PRP induced an inflammatory cytokine response in joints, whereas resting or CaCl2-activated PRP did not. Synovial growth factor levels were low overall; the reported benefits of intra-articular PRP may not be attributable to changes in local PDGF or TGFβ1 concentrations.

Equine myeloperoxidase: A novel biomarker in synovial fluid for the diagnosis of infection

Equine joint infection is a life-threatening disorder, and confirmation of the diagnosis can be difficult. Synovial fluid biomarkers may assist the discrimination between infectious and noninfectious joint disease. This study investigates whether the immunological detection of total and enzymatically active myeloperoxidase (MPO) assists the diagnosis of joint infection in horses. The following 4 sample groups were included: healthy; osteochondritis dissecans (OCD); traumatic synovitis; and culture-confirmed infected joints. Synovial fluid was analysed for total MPO by a horse-specific sandwich enzyme-linked immunosorbent assay (ELISA) and for active MPO using the specific immunological extraction followed by enzymatic detection (SIEFED) technique. Western blot analysis was performed to confirm the antibody specificity. Synovial fluid from infected joints contained significantly more total and active MPO than samples from healthy joints, joints affected by OCD and joints with traumatic synovitis. Cut-off values were set at 5000 and 350 ng/ml for total and active MPO, respectively, with fair sensitivity, specificity, positive and negative predictive values and likelihood ratios for infection. Correlation coefficients were reported between the total as well as the active MPO levels and the routine synovial fluid parameters, i.e. the white blood cell count, the neutrophil count and the total protein level. No correlation was observed between MPO and either the age of the horse or the joint affected. Western blotting confirmed the antibody specificity for equine MPO. Synovial fluid MPO was identified as a very promising biomarker to augment the discrimination of infectious vs. noninfectious joint disease in horses. Both ELISA and SIEFED techniques can be used for its specific and rapid detection. The analysis of synovial fluid MPO can be used as a complementary test to aid in the discrimination between infectious and noninfectious joint disease, especially when the white blood cell counts and the total protein level are inconclusive.

Analgesic and anti-hyperalgesic effects of epidural morphine in an equine LPS-induced acute synovitis model

Epidural morphine is widely used in veterinary medicine, but there is no information about the anti-hyperalgesic and anti-inflammatory effects in acute inflammatory joint disease in horses. The analgesic, anti-hyperalgesic and anti-inflammatory effects of epidural morphine (100mg/animal or 0.17 ± 0.02 mg/kg) were therefore investigated in horses with acute synovitis. In a cross-over study, synovitis was induced in the talocrural joint by intra-articular lipopolysaccharide (LPS). The effect of epidural morphine was evaluated using physiological, kinematic and behavioural variables. Ranges of motion (ROM) of the metatarsophalangeal and talocrural joints were measured, clinical lameness scores and mechanical nociceptive thresholds (MNTs) were assessed and synovial fluid inflammatory markers were measured. The injection of LPS induced transient synovitis, resulting in clinical lameness, decreased ranges of motion in the talocrural and metatarsophalangeal joints, decreased limb loading at rest and increased composite pain scores. Epidural morphine resulted in a significant improvement in clinical lameness, increased ROM and improved loading of the LPS-injected limb at rest, with no effects on synovial fluid inflammatory markers. Morphine prevented a decrease in MNT and, hence, inhibited the development of hyperalgesia close to the dorsal aspect of inflamed talocrural joints. This study showed that epidural morphine provides analgesic and anti-hyperalgesic effects in horses with acute synovitis, without exerting peripheral anti-inflammatory effects.