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Topic:Musculoskeletal System
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.
Macroscopic changes in the distal ends of the third metacarpal and metatarsal bones of Thoroughbred racehorses with condylar fractures. To determine changes in the distal ends of the third metacarpal and metatarsal bones (MCIII and MTIII) of Thoroughbred racehorses that had sustained a catastrophic condylar fracture during high-speed exercise. Methods: Fractured and contralateral MCIIIs and MTIIIs from 11 Thoroughbred racehorses that sustained a displaced condylar fracture during racing, both MCIIIs from 5 Thoroughbred racehorses euthanatized because of a catastrophic injury other than a condylar fracture, and both MCIIIs from 5 horses of other breeds that had not been professionally trained or raced. Methods: Macroscopic obse...
Speed of sound measurements of the third metacarpal bone in young exercising thoroughbred racehorses. The purpose of this longitudinal in-field study was to evaluate the influence of exercise, age, and gender on superficial cortical bone of the third metacarpal bone (MC III) in young Thoroughbreds by measuring speed of sound (SOS) values with an axial transmission technique (Omnisense, Sunlight Ltd, Israel). Both MC III of 75 racehorses, 2 to 4 years old, were monitored with SOS measurements in 5- to 7-week intervals during a 9- month physical exercise period. Medical data and training programs (slow gallop, canter, and high-speed work) of each horse were recorded. SOS measurements began befor...
Significant exercise-related changes in the serum levels of two biomarkers of collagen metabolism in young horses. To identify metabolic biomarkers that can be evaluated in serum for monitoring the effects of exercise on skeletal development in mammals. Methods: Sera of foals from three groups (box-stall rest, pasture and training) were serially collected over the first 5 months of life and assayed for eight biomarkers of cartilage and bone metabolism. Sub-populations from each group were sampled for an additional 6 months of identical exercise. Results: When expressed as a percentage of baseline values, lower serum levels of the carboxy-terminal propeptides of type II collagen (CPII), and higher serum lev...
Ultrasonography of peripheral nerves in the normal adult horse. A study of the ultrasonographic appearance and size of the sciatic, tibial, peroneal, suprascapular, radial, median, and ulnar nerves and a comparison with the anatomic size and location of these nerves in the normal adult horse is reported. Cadavers and live horses were studied. Landmarks for localization and techniques for nerve identification are described. The depth and diameter of each nerve at various locations and the success rate in imaging each nerve are reported. Statistically significant correlations were found between anatomically and ultrasonographically measured nerve depths and ...
The real response of bone to exercise. This review presents findings made in studies of large mammalian bones, especially from racehorse training experiments (2-8 years old, third metacarpal, tarsal) and human autopsy orthopaedic femoral implant retrievals and other human biopsy and autopsy cases. Samples were cleaned to analyse mineralized matrix in three dimensions, or poly methyl-methacrylate embedded and micromilled to delete topography and study the superficial c. 0.5-microm two-dimensional section using quantitative backscattered electron imaging. With experimental implant studies in rabbits, observations were also made in vi...
Differential expression of equine myosin heavy-chain mRNA and protein isoforms in a limb muscle. The horse is one of the few animals kept and bred for its athletic performance and is therefore an interesting model for human sports performance. The regulation of the development of equine locomotion in the first year of life, and the influence of early training on later performance, are largely unknown. The major structural protein in skeletal muscle, myosin heavy-chain (MyHC), is believed to be primarily transcriptionally controlled. To investigate the expression of the MyHC genes at the transcriptional level, we isolated cDNAs encoding the equine MyHC isoforms type 1 (slow), type 2a (fast...
The regulation of respiratory resistance in exercising horses. Horses display remarkable aerobic capabilities, attaining during muscular exercise a maximal rate of oxygen consumption about 30-fold higher than the resting value, and 2.5-fold higher than that of other mammals of similar body mass. Under these circumstances an enormous mechanical burden is expected to impinge on the equine respiratory pump and regulatory mechanisms aiming to minimize this load may play an important role in determining the adequacy of the respiratory system to the metabolic requirements. The behaviour of the respiratory system has been investigated in horses at rest and durin...
Architectural properties of distal forelimb muscles in horses, Equus caballus. Articular injuries in athletic horses are associated with large forces from ground impact and from muscular contraction. To accurately and noninvasively predict muscle and joint contact forces, a detailed model of musculoskeletal geometry and muscle architecture is required. Moreover, muscle architectural data can increase our understanding of the relationship between muscle structure and function in the equine distal forelimb. Muscle architectural data were collected from seven limbs obtained from five thoroughbred and thoroughbred-cross horses. Muscle belly rest length, tendon rest length, m...
Muscarinic receptor subtypes mediate vasorelaxation in isolated horse deep dorsal penile vein. To investigate the effect of acetylcholine (ACh) on horse deep dorsal penile vein and to characterize the muscarinic receptor subtypes involved in this response. Methods: Vein rings were mounted in an organ bath chamber, and the isometric tension was recorded. Results: In phenylephrine-contracted veins, ACh (1 nM to 1 microM) induced endothelium-dependent relaxation. The muscarinic receptor antagonist, atropine, produced parallel rightward shifts of the ACh response curves (pA2 = 10.04; pK(B) = 9.98). Carbachol (10 nM to 100 microM) also evoked relaxation in the vein segments, but showed a low...
Force- and moment-generating capacities of muscles in the distal forelimb of the horse. A detailed musculoskeletal model of the distal equine forelimb was developed to study the influence of musculoskeletal geometry (i.e. muscle paths) and muscle physiology (i.e. force-length properties) on the force- and moment-generating capacities of muscles crossing the carpal and metacarpophalangeal joints. The distal forelimb skeleton was represented as a five degree-of-freedom kinematic linkage comprised of eight bones (humerus, radius and ulna combined, proximal carpus, distal carpus, metacarpus, proximal phalanx, intermediate phalanx and distal phalanx) and seven joints (elbow, radiocarp...
The application of a scintigraphic grading system to equine tibial stress fractures: 42 cases. Tibial stress fractures are an important cause of lameness in the Thoroughbred racehorse. While it is recognised that these injuries can vary in clinical presentation and radiographic or scintigraphic appearance, little has been done to quantify lesion severity. By contrast the scintigraphic grading of tibial stress fractures in human athletes is widely reported and assists in the selection of appropriate management regimes. Objective: To determine the relationship between scintigraphic grade, clinical severity and radiographic appearance of tibial stress fractures. Methods: The current study ...
Radiographic changes in Thoroughbred yearlings. Part 1: Prevalence at the time of the yearling sales. Radiography in presale examinations of TB yearlings has become standard practice in recent years. Objective: To describe the prevalence and distribution of radiographic changes in the fetlocks, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings in central Kentucky when these joints were examined as part of routine pre- and post sale evaluations. Methods: Horses subjected to radiographs included the fore (n = 1127) and hind (n = 1102) fetlocks, carpi (n = 1130), tarsi (n = 1101), stifles (n = 660) and fore feet (n = 300). Radiographic changes were categorised by location and type of ...
Correlation of racing performance with radiographic changes in the proximal sesamoid bones of 487 Thoroughbred yearlings. Proximal sesamoiditis has been a common and confusing radiographic diagnosis in Thoroughbred yearling surveys. This study categorised the radiographic appearance of yearling proximal sesamoid bones and determined their effect on the number of races started and earning potential for racing at ages 2 and 3 years. Objective: Yearlings with moderate to severe proximal sesamoiditis have decreased performance at age 2 and 3 years. Methods: Survey radiographs of 487 Thoroughbred yearlings were reviewed. Proximal sesamoid bones were examined and findings placed into 7 categories, 5 of which measured s...
Meniscal tears in horses: an evaluation of clinical signs and arthroscopic treatment of 80 cases. There is little published information available describing clinical signs, arthroscopic findings and prognosis of meniscal injuries in horses. Objective: To evaluate the effect on the outcome not only of the arthroscopic findings and treatment, but also of the clinical and radiographic signs in these horses. Methods: The following were recorded for each case: the meniscal injury, graded according to severity; clinical and radiographic findings prior to surgery; any concurrent injury in the joint seen at arthroscopy. The effect of these factors and the grade of injury on the outcome were analys...
Preliminary evidence for dormant clostridial spores in equine skeletal muscle. Clostridial myonecrosis is caused by histotoxic or tissue-
destroying clostridia (Allen et al. 1999). Clostridium perfringens
and C. septicum are the most common isolates in horses, followed
by C. chauvoei, C. novyi and C. fallax (McLaughlin et al. 1979;
Westman et al. 1979; Hagemoser et al. 1980; Murphy 1980; Van
Heerden and Botha 1982; Coloe et al. 1983; Valberg and
McKinnon 1984; Rebhun et al. 1985; Perdrizet et al. 1987). The
disease is characterised by a rapid spread of tissue necrosis
combined with a lack of leucocyte infiltration at the site of
infection (Stevens et al. 1987). ...
Dynamic compressive strain inhibits nitric oxide synthesis by equine chondrocytes isolated from different areas of the cartilage surface. Chondrocytes within articular cartilage respond to the mechanical stresses associated with normal joint loading via a series of signalling pathways. Specific biomolecules, such as nitric oxide (NO), have been implicated in these mechanotransduction processes. It has been shown that the synthesis of NO can be inhibited by dynamic compressive strain of chondrocytes in vitro which, in turn, leads to an up-regulation of specific metabolic parameters. Objective: Chondrocytes isolated from different joint locations and seeded in agarose constructs respond in a distinct manner to the application of d...
Use of a dynamic compression plate and a cable cerclage system for repair of a fracture of the radius in a horse. A pregnant 9-year-old Peruvian Paso mare was evaluated because of a fracture involving the left radius. On examination, grade IV/V lameness of the left forelimb was observed; radiography of the limb revealed a longitudinal oblique displaced fracture that extended from the caudal cortex of the radial mid-diaphysis into the humeroradial joint. To minimize the development of degenerative joint disease in the humeroradial joint, repair with internal fixation was recommended. A dynamic compression plate was applied to the cranial aspect of the radius; three 2-mm stainless steel cable cerclages were...
Demographic and clinical characteristics of geriatric horses: 467 cases (1989-1999). To describe the demographic and clinical characteristics of a population of geriatric horses. Methods: Retrospective study. Methods: 467 horses that were > or = 20 years of age. Methods: Medical records of 539 geriatric horses that were evaluated at a university large animal hospital between 1989 and 1999 were reviewed. Data collected included signalment, reason for evaluation, specific diagnoses, surgical procedures, inpatient or outpatient care, duration of hospitalization, and outcome. Results: 467 horses met the criteria for inclusion in the study. Horses that were > or = 20 years of age c...
Molecular cloning of equine muscle-type phosphofructokinase cDNA. The complete coding region sequence of equine muscle-type phosphofructokinase (ePFKM) was obtained from skeletal muscle of a thoroughbred horse. The deduced amino acid sequence of ePFKM showed 97%, 96%, 96%, 96% and 95% identity to canine, human, mouse, rabbit and rat PFKM, respectively. The amino and carboxyl terminal halves of ePFKM presented a structure of tandem repeat, as other mammalian PFKMs. As the amino acid residues constituting various ligand-binding sites were also conserved, it is thought that ePFKM has enzymatic activity similar to PFKM in other mammals.
Are uniform regional safety factors an objective of adaptive modeling/remodeling in cortical bone? It has been hypothesized that a major objective of morphological adaptation in limb-bone diaphyses is the achievement of uniform regional safety factors between discrete cortical locations (e.g. between cranial and caudal cortices at mid-diaphysis). This hypothesis has been tested, and appears to be supported in the diaphyses of ovine and equine radii. The present study more rigorously examined this question using the equine third metacarpal (MC3), which has had functionally generated intracortical strains estimated by a sophisticated finite element model. Mechanical properties of multiple mid...
Prevalence of Sarcocystis infection in horses in Mongolia. Sarcocystis infection was detected in 93% of horses in Mongolia. Using the compress method, sarcocysts were found in the muscles of the diaphragm, heart and tongue in 40 of the 43 horses that were slaughtered at the Makh Impex Meat Company in Ulaan Baatar in July 1998. The muscle of the tongue showed the highest rate (97.5%) of infection. The distribution of sarcocysts in the muscles was positively correlated with horse age; the rate of detection was significantly lower (p=0.01) in the under 10 year old group than the older group. All horses were apparently healthy and were slaughtered for hum...
Investigations into the role of the thyrohyoid muscles in the pathogenesis of dorsal displacement of the soft palate in horses. Contributes to the understanding of the pathogenesis of dorsal displacement of the soft palate during exercise so that management of this condition could be enhanced. Objective: That the thyrohyoid muscles play an important role in the stability of the laryngo-palatal relationship and that dysfunction of these muscles leads to dorsal displacement of the soft palate (DDSP) during exercise. Methods: Ten horses were exercised on a high-speed treadmill under 4 different treatment conditions: control conditions (n = 10), after resection of thyrohyoid muscles (TH, n = 10), after sham-treatment (n = ...
Are the material properties and matrix composition of equine flexor and extensor tendons determined by their functions? Injury to the superficial digital flexor tendon (SDFT) is common in competition horses. The SDFT contributes to locomotory efficiency by storing energy; such tendons have low safety margins. Tendons which merely position the limb, including the opposing common digital extensor tendon (CDET), are rarely injured. The current failure of strategies to prevent or effectively treat injury to the SDFT indicates the importance of understanding how it differs from tendons which are not injury-prone. Objective: That the structural and material properties and matrix composition of the SDFT and CDET diffe...
The sacroiliac joints: evaluation using nuclear scintigraphy. Part 1: The normal horse. Sacroiliac (SI) disease is recognised as a cause of poor hindlimb action but differential diagnosis is often difficult. Objective: That in clinically normal horses there would be a significant difference in the ratio of radiopharmaceutical uptake (RU) between the fifth lumbar vertebra (L5) and each tuber sacrale (TS) and between L5 and each SI joint; and that these ratios would alter with age, but ratios would be bilaterally symmetrical. Methods: Dorsal scintigraphic images of the SI region of 15 horses, selected randomly from the clinic database, were analysed by 2 of the authors, comparing n...
Pain associated with the sacroiliac joint region: a clinical study of 74 horses. There has been no large study of horses with suspected sacroiliac (SI) joint region pain in which the clinical diagnosis has been supported by either abnormal radiopharmaceutical activity in the SI joint region or by periarticular infiltration of local anaesthetic solution. Objective: To describe the clinical features of horses with SI joint region pain, to document the age, breed, sex, discipline, size and conformation of affected horses and to compare these with the author's (SD) normal case population and to document the results of infiltration of local anaesthetic solution around the SI jo...
The equine hind limb is actively stabilized during standing. Horses spend much of their life standing, and they are believed to be able to keep their limbs straight without muscular effort. We tested the hypothesis that the stifle (knee) and hock (tarsal) joints could be stabilized merely with the help of a passive lock mechanism whereby the patella is secured behind a hook, formed by the medial femoral trochlea. In anaesthetized animals and isolated limbs the stifle and hock flex readily under compression. In isolated limbs this collapse was prevented by a small force applied to the patella, mimicking the action of the vastus medialis muscle. In vivo, ...
Computed tomographic anatomy of the equine tarsus. The purpose of this study was to provide a detailed computed tomographic (CT) anatomic reference for the equine tarsus. CT examinations of the tarsal regions from four clinically and radiographically normal adult horses, which were euthanized for reasons not related to musculoskeletal disease, were included in the study. Limbs were removed at the level of midtibia, and 3-mm contiguous transverse CT images were obtained, starting at a level proximal to the tuber calcanei and continuing distally into the proximal metatarsus. Soft tissue and bone windows were used to image different anatomic feat...
Osteon pullout in the equine third metacarpal bone: effects of ex vivo fatigue. An important concept in bone mechanics is that osteons influence mechanical properties in several ways, including contributing to toughness and fatigue strength by debonding from the interstitial matrix so as to "bridge" developing cracks. Observations of "pulled out" osteons on fracture surfaces are thought to be indicative of such behavior. We tested the hypothesis that osteon pullout varies with mode of loading (fatigue vs. monotonic), cortical region, elastic modulus, and fatigue life. Mid-diaphseal beams from the dorsal, medial, and lateral regions of the equine third metacarpal bone were...
Quantitative electromyographic examination in myogenic disorders of 6 horses. Electromyographic needle examination (EMG), including the semiautomatic quantitative analysis of motor unit action potential (MUAP), is an important diagnostic tool for myopathy in humans. The diagnostic possibilities of this technique have not been fully explored in horses; however, recent studies have shown that MUAP analysis can be performed in conscious horses. To determine the diagnostic possibilities of EMG in horses, we compared the EMG results of the subclavian muscle, the triceps, and the lateral vastus muscle in 6 equine patients thought to have myogenic disorders with those in 7 nor...
