Synovitis in horses refers to the inflammation of the synovial membrane, which lines the joints and tendon sheaths. This condition can result from various causes, including trauma, overuse, or underlying joint disease, and often leads to joint pain and swelling. Synovitis is a significant concern in equine medicine as it can affect a horse's mobility and performance. The synovial membrane produces synovial fluid, which lubricates the joint and provides nutrients to the cartilage. Inflammation can alter the production and composition of this fluid, impacting joint health. This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, pathophysiology, and management of synovitis in horses.
Moore RM, Schneider RK.Arthroscopy was performed in 1 carpal joint unilaterally in 27 horses and either in 2 carpal joints unilaterally or 1 carpal joint bilaterally in 7 horses. All horses were lame, but the cause of lameness could not be determined from radiographs. Twenty-seven carpi did not have radiographically visible abnormalities; the remaining 14 had only mild to moderate lucency or sclerosis of the radial facet of the third carpal bone. The primary abnormalities identified during arthroscopy included a crush fracture of the third carpal bone (7 carpi), an incomplete fracture of the third carpal bone in the...
Owens JG, Kamerling SG, Barker SA.The pharmacokinetic properties of a single intravenous dose of ketoprofen (2.2 mg/kg) in plasma and synovial fluid were compared in four healthy animals and four horses with experimentally induced acute synovitis. Synovitis was induced by the injection of a 1% solution of sterile carrageenan into the left intercarpal joint. Ketoprofen was administered at the same time as carrageenan infection. The plasma disposition followed a biexponential equation or a two-compartment model in most horses. The plasma harmonic mean half-life in healthy horses (0.88 h) was longer than in horses with synovitis ...
Osborne AC, Carter SD, May SA, Bennett D.An investigation was made into the possible contribution of autoimmune mechanisms to equine arthropathies. Serum and synovial fluid (SF) immune complexes and anti-collagen Type II antibodies were measured, by ELISA, in groups of horses with naturally occurring osteoarthritis (OA), osteochondritis dissecans (OCD), bone fracture, traumatised joints, synovitis, infected joints and non-diseased (control) joints. Significantly raised anti-collagen Type II antibodies were found in osteoarthritic (P < 0.02) and traumatised joint synovial fluids (P < 0.01) compared with the control, where ten of...
Major MD, Grant BD, White KK, Ratzlaff MH, Gallina AM, Donati RM.The suspensory apparatus of one forelimb was surgically disrupted in six adult horses by transecting the distal sesamoidean ligaments. A double-braided prosthetic ligament made of aramid yarn was installed to support the flexor surface of the metacarpophalangeal joint. The prosthesis was routed through tunnels in the third metacarpal bone and proximal phalanx, and secured to bone with screws. Evaluation by radiography, synovial fluid analysis, cinematography, and dynamography was performed before surgery and at weeks 16 and 30. Supracondylar cortical lysis and periosteal proliferation were obs...
Welch RD, Watkins JP, DeBowes RM, Leipold HW.The effects of intra-articular administration of dimethylsulfoxide (DMSO) on chemically induced synovitis in the middle carpal joint of 6 weanling horses were evaluated. Following aseptic collection of synovial fluid, the middle carpal joint of each forelimb was injected with 50 mg of Na-monoiodoacetate to induce synovitis. Eight days after injection, synovial fluid was obtained and the right middle carpal joints were injected with 2 ml of 40% DMSO in lactated Ringer solution. The corresponding joints of the left limb (control) were injected with 2 ml of lactated Ringer solution. Sampling and ...
Crawford WH, Houge JC, Neirby DT, Di Mino A, Di Mino AA.The effect of pulsed radio frequency therapy (PRFT) was evaluated on seven ponies with no arthritis and in 28 ponies in which arthritis was created using intra-articular amphotericin B to induce synovitis in the right middle carpal joint. The ponies were divided into five treatment and two control groups. Two levels of arthritis were created and two dosage levels of PRFT were evaluated. The effect of PRFT on arthritic and nonarthritic joints was measured by comparing synovial fluid parameters, the degree and duration of lameness, the range of carpal motion, and carpus circumference, for treate...
Geor RJ, Clark EG, Haines DM, Napier PG.Systemic lupus erythematosus (SLE) was diagnosed in a 2-year-old Standardbred filly. Clinical signs of SLE included weight loss, bilateral symmetric alopecia, seborrhea, oral ulceration, and lymphadenopathy. Abnormal laboratory findings included a Coombs test-positive hemolytic anemia and positive antinuclear antibody test result. Histologic evaluation of multiple skin biopsy specimens revealed interface dermatitis with linear deposition of IgG at the basement membrane zones of the epidermis and hair follicles. The filly did not respond to glucocorticoid treatment and was euthanatized. Necrops...
Baird AN, Scruggs DW, Watkins JP, Taylor TS.Sixteen horses were allotted to 4 groups of 4 horses each to evaluate the effect of tendon sheath lavage with 4 solutions (balanced electrolyte solution, 0.1% povidone-iodine, 0.5% povidone-iodine, and 0.5% chlorhexidine). The synovitis caused by 0.1% povidone-iodine lavage was not appreciably worse than that caused by balanced electrolyte solution lavage, but the 0.5% povidone-iodine and chlorhexidine lavages caused severe synovitis, and, therefore, should not be used for tendon sheath lavage.
Foerner JJ, McIlwraith CW.This article attempts to address what the authors consider to be the major orthopedic problems in the racehorse, with particular attention to their treatment and prognosis. These problems include fractures, osteochondral fragments, synovitis, degenerative joint disease, tendinitis, desmitis, osteochondritis dissecans, and subchondral cystic lesions of the joints.
Kannegieter NJ, Burbidge HM.The radiographic and arthroscopic findings in 150 carpal joints in 114 lame horses were compared. Chip, slab, or sagittal fractures were identified in 130 (87%) joints. In 101 (78%) of these there was good agreement between radiographic and arthroscopic findings on the number and position of fractures. In 23 (18%) joints, chip fractures additional to those seen radiographically were found arthroscopically. In one joint a large chip fracture from the craniolateral aspect of the distal radius was identified only by arthroscopy, while in 6 joints fractures were identified only by radiography. Obs...
Goodman NL, Baker BK.Lameness problems constitute a major part of racing Quarter Horse practice. This article considers the diagnosis, prognosis, and treatment of the frequently encountered lamenesses. The main conditions included are synovitis, intra-articular fractures, osteochondritis dissecans, and degenerative joint disease as they relate to the coffin, fetlock, carpal, and tarsal joints. Intra-articular injection techniques and medications are discussed because of the frequency of joint disease. Bucked shins and stress fractures are also reviewed.
Auer DE.The role of oxygen-derived free radicals is considered critical to the etio-pathogenesis of equine inflammatory joint disease. In vivo, the superoxide radical in the joint may be derived either from activated polymorphonuclear leukocytes or from an ischemia/reperfusion cycle. In the presence of ferrous iron, it may generate the highly reactive hydroxyl radical (OH *). Predisposing factors may include synovitis, exercise-induced ischemia and minor traumatic injury to the joints. Unlike other inflammatory mediators, oxygen-derived free radicals may damage tissue directly and these reactive speci...
McIlwraith CW, Vachon A.Treatment of degenerative joint disease (osteoarthritis) is discussed in relationship to pathogenesis of five clinical entities, defined to facilitate discussion:-1) occurring in high motion joints and associated with synovitis; 2) associated with low motion joints; 3) "non-progressive" articular cartilage erosion; 4) secondary to other identified problems (intra-articular fractures, ligamentous damage, wounds, septic arthritis, osteochondrosis); and 5) chondromalacia of the patella. In addition to direct damage to articular cartilage, synovitis and capsulitis and depletion of matrical glycosa...
Sweeney CR, Sweeney RW, Divers TJ.Case records of 48 foals with pneumonia due to Rhodococcus equi were reviewed. Twenty of the 48 foals survived and 28 died or were euthanized. There was no significant difference between the survivors and non-survivors in the age of onset of illness, duration of illness prior to admission, the mean white blood cell (WBC) count, or the mean plasma fibrinogen content. All foals had R. equi isolated from a tracheobronchial aspirate or lung specimens obtained at necropsy. All organisms were susceptible in vitro (Kirby-Bauer) to erythromycin and gentamicin. Susceptibilities to other drugs were: tri...
Dik KJ.Radiographically, joint ill in foals is subdivided into four different types: Type P - osteomyelitis in the meta- and/or epiphysis adjacent to the physis. Type E - osteomyelitis in the epiphyseal subchondral bone. Type S - synovitis confined to the joint itself. Type T - osteomyelitis in the small tarsal bones. The radiographical features corresponding with the different types, the relationship between the radiological, pathological, bacterial and clinical findings, and the recommended radiographic procedure are discussed in detail.
Gerring EL, Webbon PM.Restriction of free movement of the flexor tendons through the fetlock canal results in lameness. The commonest cause was chronic synovitis of the digital sheath. The condition is characterised by an unremitting lameness, synovial distension and a notch on the caudal aspect of the limb. The condition can be relieved by section of the annular ligament of the fetlock. In a series of 24 cases 16 horses returned to work with no recurrence of lameness, three cases were lost to follow up and five animals remained lame; three of these had intercurrent disease.
McIlwraith CW.Current concepts of pathogenesis, diagnosis, and treatment of equine degenerative joint disease are presented on the basis of recently acquired experimental and clinical knowledge. A number of concepts of pathogenesis need modification and the rationale of some of the newer treatments requires definition. Synovitis and other soft tissue changes are important components of the pathogenesis in addition to direct trauma to the articular cartilage. Loss of glycosaminoglycans constitutes an important biochemical "lesion" in the articular cartilage, making it weak and susceptible to trauma. Recognit...
van Veenendaal JC, Moffatt RE.Eight cases of sessile, intra-articular soft tissue masses originating from the cranio-dorsal attachment of the capsule of the fetlock joint of horses are presented. In 4 of these cases an osteochondral fracture of the first phalanx was also present. Clinically the condition closely resembled villonodular synovitis; however the microscopic changes did not correspond to those reported. The clinical signs included lameness after exercise, joint effusion and pain on manipulation. The offending masses were surgically resected and their histology indicated a chronic proliferative synovitis. The res...
Moore RM, Schneider RK.Arthroscopy was performed in 1 carpal joint unilaterally in 27 horses and either in 2 carpal joints unilaterally or 1 carpal joint bilaterally in 7 horses. All horses were lame, but the cause of lameness could not be determined from radiographs. Twenty-seven carpi did not have radiographically visible abnormalities; the remaining 14 had only mild to moderate lucency or sclerosis of the radial facet of the third carpal bone. The primary abnormalities identified during arthroscopy included a crush fracture of the third carpal bone (7 carpi), an incomplete fracture of the third carpal bone in the...
Osborne AC, Carter SD, May SA, Bennett D.An investigation was made into the possible contribution of autoimmune mechanisms to equine arthropathies. Serum and synovial fluid (SF) immune complexes and anti-collagen Type II antibodies were measured, by ELISA, in groups of horses with naturally occurring osteoarthritis (OA), osteochondritis dissecans (OCD), bone fracture, traumatised joints, synovitis, infected joints and non-diseased (control) joints. Significantly raised anti-collagen Type II antibodies were found in osteoarthritic (P < 0.02) and traumatised joint synovial fluids (P < 0.01) compared with the control, where ten of...
Auer DE.The role of oxygen-derived free radicals is considered critical to the etio-pathogenesis of equine inflammatory joint disease. In vivo, the superoxide radical in the joint may be derived either from activated polymorphonuclear leukocytes or from an ischemia/reperfusion cycle. In the presence of ferrous iron, it may generate the highly reactive hydroxyl radical (OH *). Predisposing factors may include synovitis, exercise-induced ischemia and minor traumatic injury to the joints. Unlike other inflammatory mediators, oxygen-derived free radicals may damage tissue directly and these reactive speci...
Strand E, Martin GS, Crawford MP, Kamerling SG, Burba DJ.The objective of this study was to determine if intraarticular pressure, elastance of the soft tissue forming the dorsal pouch, and range of motion in flexion measurements are significantly different in Thoroughbred metacarpophalangeal joints with clinical evidence of idiopathic synovitis, primary synovitis, synovitis/capsulitis, or osteoarthritis relative to clinically normal joints. Forty-two metacarpophalangeal joints, in 25 active or retired Thoroughbred racehorses, were categorised by palpation and visual inspection of the palmar pouch into one of 4 increasing grades of distention. Intra-...
Birckhead EM, Das S, Tidd N, Raidal SL, Raidal SR.Septic synovitis and peritonitis are routinely diagnosed in horses based on clinical examination findings and laboratory assessment of synoviocentesis and abdominocentesis samples, respectively. Diagnosis is difficult in some cases because of an overlap in laboratory results for septic and non-septic inflammation. Neutrophil extracellular trap (NET) formation is part of the innate immune response against pathogens. Identifying and quantifying NETs, which have not been explored in clinical samples from horses with septic synovitis and peritonitis, to our knowledge, may be helpful in detecting i...
Everett JB, Menarim BC, Barrett SH, Bogers SH, Byron CR, Pleasant RS, Werre SR, Dahlgren LA.Osteoarthritis (OA) can be debilitating and is related to impaired resolution of synovial inflammation. Current treatments offer temporary relief of clinical signs, but have potentially deleterious side effects. Bone marrow mononuclear cells (BMNC) are a rich source of macrophage progenitors that have the ability to reduce OA symptoms in people and inflammation in experimentally-induced synovitis in horses. The objective of this study was to evaluate the ability of intra-articular BMNC therapy to improve clinical signs of naturally occurring equine OA. Horses presenting with clinical and radio...
Munoz Moran JA.This study was performed to evaluate the efficacy of intra-articular (IA) injections of a combination of platelet rich plasma (PRP) and hyaluronic acid (HA) on joint effusion following arthroscopic removal of OCD in the tarso-crural joint (TCJ) in young Andalusian horses. Methods: Forty Andalusian horses diagnosed with OCD of the distal intermediate ridge of the tibia (DIRT) were included in the study. Horses enrolled in this study had persisting synovial effusion after arthroscopic removal of OCD in the TCJ. A subjective semi-quantitative effusion score was adopted in the study to define the ...
Duggan MJS, Kearney C, Baltrimaite M, Labberté MC, Gibney R, Brama PAJ.The aim of this study was to refine the lipopolysaccharide (LPS)-induced synovitis model in normal carpal joints of Thoroughbred horses by comparing two low LPS doses. A further aim was to investigate the relationship between the induced synovitis and lameness. The study design consisted of two phases using nine horses with a unilateral crossover design and a within-animal saline control. Synoviocentesis was performed at post-injection hour (PIH) 0, 8, 24, 72 and 168, allowing for synovial fluid cytology and biomarker analysis. Objective gait and thermographic analysis were used to objectively...
Foerner JJ, McIlwraith CW.This article attempts to address what the authors consider to be the major orthopedic problems in the racehorse, with particular attention to their treatment and prognosis. These problems include fractures, osteochondral fragments, synovitis, degenerative joint disease, tendinitis, desmitis, osteochondritis dissecans, and subchondral cystic lesions of the joints.
Baird AN, Scruggs DW, Watkins JP, Taylor TS.Sixteen horses were allotted to 4 groups of 4 horses each to evaluate the effect of tendon sheath lavage with 4 solutions (balanced electrolyte solution, 0.1% povidone-iodine, 0.5% povidone-iodine, and 0.5% chlorhexidine). The synovitis caused by 0.1% povidone-iodine lavage was not appreciably worse than that caused by balanced electrolyte solution lavage, but the 0.5% povidone-iodine and chlorhexidine lavages caused severe synovitis, and, therefore, should not be used for tendon sheath lavage.
Geor RJ, Clark EG, Haines DM, Napier PG.Systemic lupus erythematosus (SLE) was diagnosed in a 2-year-old Standardbred filly. Clinical signs of SLE included weight loss, bilateral symmetric alopecia, seborrhea, oral ulceration, and lymphadenopathy. Abnormal laboratory findings included a Coombs test-positive hemolytic anemia and positive antinuclear antibody test result. Histologic evaluation of multiple skin biopsy specimens revealed interface dermatitis with linear deposition of IgG at the basement membrane zones of the epidermis and hair follicles. The filly did not respond to glucocorticoid treatment and was euthanatized. Necrops...
Roneus B, Andersson AM, Ekman S.Chronic synovitis may cause recurring lameness in competing race horses. Forty-five standardbred horses with recurring lameness secondary to chronic synovitis were studied. Arthroscopic synovectomy was performed in 32 metacarpo-/metatarsophalangeal joints and in 28 intercarpal joints of horses that had previously been treated unsuccessfully with commonly used intraarticular medication The outcome of the synovectomy was evaluated by comparing racing performance before and after surgery. The synovial membrane was microscopically characterized as chronic synovitis of varying severity. Racing perf...
Dik KJ.Radiographically, joint ill in foals is subdivided into four different types: Type P - osteomyelitis in the meta- and/or epiphysis adjacent to the physis. Type E - osteomyelitis in the epiphyseal subchondral bone. Type S - synovitis confined to the joint itself. Type T - osteomyelitis in the small tarsal bones. The radiographical features corresponding with the different types, the relationship between the radiological, pathological, bacterial and clinical findings, and the recommended radiographic procedure are discussed in detail.
Goodman NL, Baker BK.Lameness problems constitute a major part of racing Quarter Horse practice. This article considers the diagnosis, prognosis, and treatment of the frequently encountered lamenesses. The main conditions included are synovitis, intra-articular fractures, osteochondritis dissecans, and degenerative joint disease as they relate to the coffin, fetlock, carpal, and tarsal joints. Intra-articular injection techniques and medications are discussed because of the frequency of joint disease. Bucked shins and stress fractures are also reviewed.
Major MD, Grant BD, White KK, Ratzlaff MH, Gallina AM, Donati RM.The suspensory apparatus of one forelimb was surgically disrupted in six adult horses by transecting the distal sesamoidean ligaments. A double-braided prosthetic ligament made of aramid yarn was installed to support the flexor surface of the metacarpophalangeal joint. The prosthesis was routed through tunnels in the third metacarpal bone and proximal phalanx, and secured to bone with screws. Evaluation by radiography, synovial fluid analysis, cinematography, and dynamography was performed before surgery and at weeks 16 and 30. Supracondylar cortical lysis and periosteal proliferation were obs...
Fukuda K, Mita H, Kuroda T, Tamura N, Kuwano A, Sato F, Takahashi T.To clarify the anti-inflammatory effect of platelet lysate (PL) on equine persistent synovitis by using a model of synovitis induced by monoiodoacetic acid (MIA). Methods: Nonseptic synovitis was induced by administering MIA into both antebrachiocarpal joints of 6 clinically healthy horses on day 0. On days 23, 30, and 37, carpal circumference measurement and synovial fluid collection for assays (leucocytes, LDH, tumor necrosis factor-α, and TGF-β1) were performed, after which PL was injected into 1 antebrachiocarpal joint and saline into the contralateral joint. Synovium and synovial fluid ...
Serpa PBS, Bogers S, Byron C, Cardona G, Patton M.A 1-year-old American Quarter horse was presented with acute onset of right hind lameness. On physical examination, there was synovial effusion of the right tarsocrural joint. Synovial fluid cytology revealed a marked eosinophilic synovitis. Serology indicated evidence of acute and chronic infection with Borrelia burgdorferi, although PCR of the synovial fluid was negative. The filly was treated with phenylbutazone and oxytetracycline, and repeated synovial cytology indicated improvement. The filly was discharged with a prescription of minocycline for 30 days. Despite initial improvement, recu...
Barreira AP, Moreira T, Silva R, Nunes L, Lioi A, Kraus E, Altheman V, Ribeiro M, Leite C, Silva A, Almeida F, Santos Junior G, Lessa D, Alves AL.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 ...
