The musculoskeletal system in horses encompasses the bones, muscles, tendons, ligaments, and joints that facilitate movement and provide structural support. This system is essential for locomotion, athletic performance, and overall health in equine species. The equine skeleton consists of approximately 205 bones, which are connected by joints and supported by a network of muscles and connective tissues. Tendons connect muscles to bones, while ligaments link bones to other bones, contributing to joint stability. The musculoskeletal system is subject to various conditions, including injuries, degenerative diseases, and developmental disorders, which can impact a horse's mobility and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathology, and treatment of musculoskeletal conditions in horses.
Andrews FM, Spurgeon TL.The histologic and histochemical staining characteristics of the triceps brachii (long head), extensor carpi radialis, gluteus medius, vastus lateralis, biceps femoris, semimembranosus, semitendinosus, and extensor digitorum longus muscles of 8 Thoroughbreds, 2 Quarter Horses, 1 Arabian, 1 Paso Fino, and 1 Shetland Pony are described. Muscle fiber morphology, staining distribution and intensity, amount of IM connective tissue, number of IM blood vessels and IM nerves, calcium-activated adenosine triphosphatase activity (CaATPase), percentage of fibertype population, percentage of relative fibe...
Manohar M.Using radionuclide-labelled microspheres, 15 micron in diameter, we studied blood flow in the respiratory muscles (diaphragm and intercostal muscles), abdominal organs (adrenal glands, kidneys, pancreas, spleen and the small and large intestines), muscles of propulsion (gluteus medius and biceps femoris), and other working (triceps brachii and longissimus dorsi lumborum) and non-working (temporal and masseter) muscles of ponies at rest and during maximal exercise performed on a treadmill. During maximal exercise heart rate, whole body O2 consumption, cardiac output and mean aortic pressure inc...
Riemersma DJ, De Bruyn P.The cross-sectional area, collagen content, dry weight as a percentage of the wet weight and the tendon fibre percentage of the cross-sectional area of the equine hindlimb were determined in the superficial and deep digital flexor tendons and the suspensory ligament at 10, 12 and six sites between tarsus and insertion respectively. The values of each of the four parameters varied between different sites in the same tendon, between different tendons within a horse and between analogous tendons of different horses. Within a tendon the cross-sectional area was inversely proportional to the collag...
Livesey MA, Hulland TJ, Yovich JV.The research article discusses a rare case of colic in two horses, which was attributed to the existence of smooth muscle intestinal tumors. Introduction The article begins by explaining that […]
Powers BE, Stashak TS, Nixon AJ, Yovich JV, Norrdin RW.Specimens of ligamentum flavum, joint capsule, and dorsal lamina were collected at surgery or necropsy from 25 horses with cervical static stenosis. All horses had myelographic evidence of dorsal compression of the spinal cord caused by soft tissue and/or bone in the caudal cervical area, primarily at C6-7. Most horses also had radiographic evidence of degenerative joint disease of articular facets. Histologically 19 horses had osteosclerosis and cartilage retention in the dorsal lamina, and 24 horses had increased fibrocartilage at the ligamentum flavum attachment to dorsal lamina. The ligame...
McEwen SA, Hulland TJ.Thirteen horses with histories of exertional rhabdomyolysis were exercised for 20 minutes to induce clinical signs of lameness, elevated serum creatine kinase (CK), and aspartate aminotransferase (AST) activities and skeletal muscle morphologic lesions. The clinical signs exhibited by affected horses included trembling, sweating, increased rate of respiration, and restricted limb movement. Serum CK reached maximal activity between 4 and 8 hours after the exercise period and serum AST activity peaked between 24 and 48 hours. Histologically, the skeletal muscle lesions in muscle biopsies 24 hour...
Palmer SE.The prevalence of carpal fractures was determined for 211 thoroughbred and 75 standardbred racehorses. Statistically significant differences were found in the location of fractures between the 2 breeds. In the thoroughbred and standardbred groups, total fractures (460) were distributed nearly equally between the left (224) and right (236) carpi. The most common site of fracture in the thoroughbred group was the distal aspect of the radiocarpal bone (112), whereas the most common site of fracture in standardbred horses was the proximal surface of the third carpal bone (61). Slab fractures were ...
Jeffcott LB, McCartney RN, Speirs VC.A safe, non-invasive method for the accurate measurement of bone mineral content in the third metacarpal bone of the horse is described. The technique involves scanning the bone with a single photon beam from an Americium-241 source. Data were obtained from the excised metacarpal bones from both forelimbs of 50 normal and seven lame horses. Measurements were made in vivo on eight normal and seven lame horses and on one experimental horse with osteopenia induced by partial weightlessness in a flotation tank. In the normal horses bone mineral content altered with age, particularly in the first s...
Dyson SJ, Greet TR.ALTHOUGH diaphyseal and distal metaphyseal fractures of
the equine humerus have been discussed in the literature
(Johnson, Lowe, Fessler and Amstutz 1974; Vaughan and
Mason 1975; Turner 1984), reports of humeral fractures of
other configurations are rare. Allen and White (1984) described
the successful surgical treatment of a chip fracture of the greater
tubercle of the humerus. This report describes the clinical
features and treatment of a fracture of the deltoid tuberosity.
Speirs VC, Anderson GA, Bourke JM.The efficacy of treating carpal lesions by arthrotomy was evaluated in 210 Thoroughbred racehorses, using survival analysis to compare their racing performances and earnings with those of 840 control horses. The treated horses were significantly inferior with respect to races contested, and wins plus places (P less than 0.001) and races won (P less than 0.01). There was no difference with respect to earnings (P less than 0.1); after adjusting for other factors, arthritis, site of fracture and presence of a displaced chip had no effect on racing performance in horses with a single-site lesion i...
Hildebrand SV, Howitt GA, Arpin D.Atracurium besylate, a recently developed, intermediate-duration acting, neuromuscular-blocking agent, was given to 15 halothane-anesthetized ponies to produce surgical relaxation (95% to 99% reduction of hoof twitch). All 15 ponies were given 3 injections; 8 of the 15 ponies were given 2 additional injections. Initial dosage of 0.11 +/- 0.01 mg/kg (mean +/- SD) and all subsequent injections of 0.052 mg/kg produced desired relaxation. Paralysis phase (maximum twitch reduction to 10% twitch recovery) lasted 24 +/- 5 minutes for the initial injection. Paralysis from subsequent injections lasted ...
MacGregor CM.Radiographic examination of the navicular bones of 258 horses was carried out. Of these 258 horses, 83 were sound (Group A), 151 had been diagnosed clinically as having navicular disease (Group B), and 24 had a forefoot lameness of unknown aetiology (Group C). Seven basic shapes of distal nutrient foramina were identified from these radiographs. A scoring system was then developed based on these different types of distal nutrient foramina. When this scoring system was applied to the radiographs of the 258 horses examined significant differences were found between the mean navicular scores of t...
Merkens HW, Schamhardt HC, Hartman W, Kersjes AW.The ground reaction force patterns from 20 clinically sound Dutch Warmblood horses (Group A) were recorded at the normal walk. The data from four to 10 stance phases of each limb were computer averaged after normalisation to the animal's body mass and to the stance time. This analysis method allowed comparison of data from left and right fore- and hindlimbs within and between horses. The left-to-right symmetry in the reaction force peaks of contralateral limbs of one horse exceeded 90 per cent. The time in the stance phase at which the peaks occur were even more symmetrically distributed. A ch...
Dempsey JA.In summary, we have shown that the design of the pulmonary system from the architectural capacities of the lung parenchyma and respiratory muscles to the remarkable, multi-level neural integration of breathing pattern and respiratory muscle recruitment is clearly intended for the exercising state. Furthermore, the system shows remarkable capability for true adaptation, both phylogenetically and even within only a few generations within a species, when preservation of the organism's ability to survive and function is at stake. At the same time there are limits to the system's homeostatic capabi...
Hauser ML.The diagnostician should be familiar with the normal ultrasound appearance (size, shape, position, and textural quality) of each structure examined. With these factors as reference points, one can describe lesions in the structure involved, the precise location and extent of the lesions, and the degree of structural compromise that is manifested. Documentation of lesions of tendons and ligaments enables one to make an accurate diagnosis and a more precise prognosis. Serial examination during the healing phases allows for a more accurate prediction as to when the structure in question can withs...
Genovese RL, Rantanen NW, Hauser ML, Simpson BS.In our 3 years of clinical experience, we have found that diagnostic ultrasound provides the veterinarian with a valuable diagnostic tool. It allows the clinician to quantify morphologic change that has occurred as a result of soft-tissue injuries, even when the clinical findings are ambiguous or insufficient. In cases in which aggressive postinjury therapy has been instituted prior to presentation, diagnostic ultrasound is often the only noninvasive method that can ascertain the extent of the horse's injury. Diagnostic ultrasound provides the technology to detect injuries before they become p...
Valentine BA, Ross CE, Bump JL, Eng VM.Intramuscular hemangiosarcoma resulting in severe anemia and thrombocytopenia was diagnosed in a 3-year-old Thoroughbred filly. Necropsy revealed multiple tumors within skeletal muscles and multiple pulmonary metastases.
Auer JA, Watkins JP, White NA, Taylor TS, Rooney JR.Fractures of the fourth carpal bone were diagnosed in 5 horses; 3 fractures were associated with fracture of the intermediate carpal bone. The diagnosis was delayed in all 5 horses, apparently because of the moderate nature of the clinical signs. Open surgical reduction with lag screw type fixation was used in all horses. Because of delayed treatment, transfixation of carpal bones (necessary for stability), and surgical trauma, degenerative joint disease with osteophyte formation occurred in all 5 horses. None of the 5 horses was able to begin or return successfully to work, although 4 of the ...
Verschooten F, Picavet TM.Desmitis of the fetlock annular ligament was diagnosed in 30 horses during a period of eight years. Most of the horses had been lame for a prolonged period and had chronically distended digital flexor tendon sheaths. Air tendograms demonstrated thickened palmar or plantar annular ligaments. In 25 horses the ligament was cut longitudinally; of these, 16 horses returned to full work without any difficulty and one became sound after a second operation. Follow up time varied from three months to seven-and-a-half years. None of the five untreated horses returned to work.
Hago BE, Vaughan LC.Contrast radiography was used to determine the position, shape, relationship and capacity of a number of tendon sheaths and bursae which have clinical significance in the horse. It was possible to establish the normal range of radiographic anatomy for these structures. Some variation in the extent and form of tendon sheaths were found between individual horses and between foals and adults.
Stashak TS.The causes, clinical signs and various approaches to treatment of injuries involving the foot and pastern regions are reviewed, and the prognosis for each type of injury is discussed.
Chopin JB, Wright JD, Melville L, Robinson WF.This report describes traumatic avulsion of the lateral collateral ligament of the humeroradial joint in a horse. The history and diagnostic procedures are included with relevant radiographs and ultrasonographs. The poor prognosis associated with this injury is due to degenerative joint disease.
Aboul-Enein HY, Van Overbeke A, Vander Weken G, Baeyens W, Oda H, Deprez P, De Kruif A.Racemic ketoprofen is a non-steroidal anti-inflammatory drug used to treat musculoskeletal and colic conditions in horses. The enantioselective chiral inversion of ketoprofen administered to horses has been studied by use of cellulose tris(4-methylbenzoate), also known as Chiralcel OJ-R, as chiral stationary phase; acetonitrile - 0.02 M perchlorate buffer (pH 2.0)-methanol, 60:15:25 (v/v/v) was used as mobile phase. Before chromatography, to effect adequate chiral interaction with the chiral stationary phase ketoprofen was derivatized with 9-aminophenanthrene, under acid conditions, after soli...
Hobbs SJ, Mather J, Rolph C, Richards J.Radial strain in normal hooves has been found to vary with strain gauge location, limb posture and sample limb but reported magnitudes were considered to be low. More accurate measurement of radial strain may enhance the understanding of hoof function. Objective: To explore in vitro radial hoof strain in relation other kinetic and kinematic variables that may be related. Methods: Five normal forelimbs were removed at the proximal articular surface of the third metacarpal bone (McIII). The limbs were loaded using a modified Instron test machine. Six calibrated infrared cameras captured movement...
Sullins KE.Indications for performing orthopedic surgery on the standing horse include inability to tolerate general anesthesia, risk of worsening an injury during recovery from anesthesia, and cost. The surgeon should be aware that performing surgery in the standing horse can be more demanding and require more experience than the same procedures when the time and convenience of general anesthesia are available. Improved sedatives and analgesics have allowed more latitude because the horses now are more tolerant than when older agents were used. Common sense should be applied to each situation before the...
McClintock SA, Hutchins DR, Laing EA, Brownlow MA.Six adult horses with normal blood gas values, normal thoracic radiographs and free from overt signs of respiratory disease were confined in flotation tanks for periods from one to seven weeks. With one exception, they all coughed, had a variable amount of nasal discharge and, at autopsy, showed cranio-ventral alterations to their lungs which were characterised by patchy irregular areas of absorption atelectasis with or without an inflammatory reaction and an accompanying alveolar emphysema.
Kotzé SH, Soley JT.Spirally arranged bundles of sub-endothelial smooth muscle enfold the small to medium-sized submucosal veins in the equine ileocecal junction. The muscle bundles, accompanied by the endothelial lining, bulge into the lumen of the vessels, partly occluding the latter. Transmission electron microscopy of the muscle cells reveals features consistent with vascular smooth muscle ultrastructure. It is proposed that the throttling effect of the muscle bundles causes engorgement of the submucosal venous plexus, which then assists in the closing of the ileocecal orifice.
Davidson EJ, Martin BB.Stress fracture of the scapula in two horses is described. Both horses had a history of acute lameness after strenuous exercise. Using elective nuclear scintigraphy focal increased radiopharmaceutical uptake in the affected scapula consistent with a fracture was identified. Standing radiography was nondiagnostic in both horses. Ultrasonographic findings in one horse were consistent with a minimally displaced incomplete fracture. Both horses were treated conservatively and returned to train and race successfully postinjury. Veterinary