Keratan sulfate (KS) is a glycosaminoglycan, distribution of which is confined mostly to hyaline cartilage. As such, it is a putative marker of hyaline cartilage catabolism. In experiment 1, a focal osteochondral defect was made arthroscopically in 1 radial carpal bone of 2 ponies, and in 2 other ponies, chymopapain was injected into the radiocarpal joint to induce cartilage catabolism. Sequential and concurrent plasma and synovial fluid concentrations of KS were measured, up to 13 months after induction of cartilage injury, to determine whether changes in KS concentrations reflected cartilage catabolism. In experiment 2, a large, bilateral osteochondral defect was made in the radial carpal bones of 18 ponies, which were subsequently given postoperative exercise and/or injected intra-articularly with 250 mg of polysulfated glycosaminoglycan (PSGAG). Medication was given at surgery, then weekly for 4 weeks. Blood samples were collected and synovial fluid was aspirated before surgery, when medication was given, and at postmortem examination (postoperative week 17). The KS concentration was measured in these fluids to determine whether changes in KS concentration indicated an effect of joint treatment. In experiment 1, the concentration of KS in synovial fluid was highest 1 day after joint injury, and the concentration in plasma peaked 2 days after joint injury. For ponies receiving chymopapain intra-articularly (generalized cartilage catabolism), a fivefold increase over baseline was observed in the concentration of KS in plasma (peak mean, 1.2 microgram/ml), and a tenfold increase over baseline in synovial fluid (peak mean, 2.0 mg/ml) was observed. On average, these maxima were threefold higher than values in fluids of ponies with osteochondral defects (focal cartilage disease). In experiment 2, nonexercised ponies had lower KS concentration (as a percentage of the preoperative concentration) in synovial fluid than did exercised ponies at all postoperative times, and.

Middle carpal cartilage explants from 4 horses with mild osteoarthritis involving that joint were maintained in tissue culture to test the effects of a polysulfated glycosaminoglycan (PSGAG) on proteoglycan synthesis and degradation. Cultures were exposed to 0.025 or 25 mg of PSGAG/ml for 48 hours, after which the medium was replaced with medium containing similar doses of PSGAG and 35S. Subsequently, the sulfated proteoglycan content of the medium and extracts of the explants was measured. Gel filtration chromatography was used to estimate the size and to purify the principal, large proteoglycan monomer, which was further characterized by digestion, using glycosidic enzymes. In a second experiment, explants were incubated with 35S for 48 hours, and were subsequently exposed to the same concentrations of the PSGAG for an additional 48 hours. The amount of remaining labeled proteoglycan was determined for culture medium and cartilage extracts. Gel filtration chromatography was used to assess the hydrodynamic size of the large proteoglycan monomer. Aliquots of proteoglycans from the second experiment were incubated in high-molecular weight hyaluronate and chromatographed to assess reaggregation. Polysulfated glycosaminoglycan caused a significant (P < 0.04) decrease in sulfated proteoglycan synthesis by cartilage explants. Radioactive proteoglycan content in explants labeled prior to exposure to PSGAG were similar. Large proteoglycan monomer size was similar in both experiments (median partition coefficient [K(AV)] = 0.40), and was not influenced by PSGAG treatment. Prelabeled explants exposed to hyaluronate and chromatographed under associative conditions had similar proportions of the radiolabel eluting as proteoglycan aggregate. Enzymatic digestion of newly synthesized large monomer revealed a mild dose-dependent increase in the proportion of keratan sulfate substitution on core protein. It was concluded that PSGAG in vitro, at the dosages evaluated, caused a decre.

In recent years, exercise on a water treadmill has come to have great relevance in rehabilitation and training centres for sport horses. Its use exploits certain physical properties of water, related to the fundamental principles of hydrodynamics, such as buoyancy, viscosity, hydrostatic pressure, and water temperature. These properties together with deliberate specification of the depth of the water and the velocity of the treadmill provide a combination of parameters that can be varied according to the purpose of the rehabilitation or training programme, the disease to rehabilitate, or the healing phase. In the current article, kinematic adaptations to exercise on a water treadmill and the direct application of such exercise to the rehabilitation of superficial and deep digital flexor tendon and accessory ligament injuries and back and joint diseases are described.

Osteoarthritis (OA) of the metacarpophalangeal joint is the most common articular disease in polo ponies leading to early retirement. A biomarker that would discriminate between pathological and physiological changes secondary to exercise could be helpful in OA prevention. The aim of this study was to investigate the effects of polo training on synovial fluid biomarkers of inflammation and cartilage turnover in polo ponies of different skill levels. Synovial fluid samples were collected from metacarpophalangeal joints of polo ponies before and during the polo season (320 d). Nucleated cells, soluble protein, prostaglandin E2 (PGE2), glycosaminoglycans (GAG), and urea were measured. The main synovial fluid GAG are chondroitin sulphate (CS, ~25 μg/mL) and hyaluronic acid (HA, ~400 μg/mL). After a polo match, a transitory increase in protein and PGE2, but not CS and HA, occurred (expressed as urea ratio), returning to basal levels in 24 h. During the polo season, the number of synovial fluid nucleated cells was always in the normal range. Increases in protein and HA occurred during the initial 40 to 80 d, returning to basal levels afterwards. In contrast, in polo prospects the concentration of CS steadily increased during the season. Long-term follow-up revealed that the synovial fluid CS was significantly higher in polo ponies that developed joint diseases within 24 months following our study. In conclusion, CS seems to be an early marker of articular cartilage damage.

Using arthroscopic technique, identical diameter defects were created in the proximal articular surface of both intermediate carpal bones of 6 horses. One of each pair of defects was deepened to penetrate the subchondral plate. Removed cartilage was assayed for [35S] sulfate incorporation, total hexosamine content, and DNA content. Six weeks later, cartilage was harvested and similarly analyzed from the distolateral portion of the radius directly opposite the created lesions and the distomedial portion of the radius distant from the lesion. The repair tissue filling the full-thickness defect and the cartilage at the periphery of the partial-thickness lesion also were analyzed. There was a marked increase in synthetic activity (35S sulfate incorporation) opposite the full-thickness defect, compared with the cartilage opposite the partial-thickness defect. A marked decrease in glycosaminoglycan content in the cartilage opposite the full-thickness defect was found as compared with that opposite the partial-thickness defect. The repair tissue filling the full-thickness defect was highly cellular, high in synthetic activity, but low in glycosaminoglycan content. Insignificant changes occurred in the cartilage adjacent to the partial-thickness defect. On the basis of these results, we suggest that full-thickness defects at 6 weeks result in more detrimental change to the cartilage opposite it than do partial-thickness lesions of the same diameter.

Four groups of 8 horses each had 1 midcarpal joint injected with 33 colony-forming units (CFU) of viable Staphylococcus aureus plus: 1 ml of saline solution (group 1, control), 250 mg of polysulfated glycosaminoglycan (PSGAG, group 2), 100 mg of methylprednisolone acetate (group 3), or 20 mg of sodium hyaulronate (group 4). Horses were euthanatized, and samples were obtained on the basis of clinical signs of septic arthritis that were nonresponsive to phenylbutazone administration. One group-1 horse, all 8 group-2 horses, 3 group-3 horses, and 4 group-horses 4 were culture-positive for S aureus and had clinical signs, results of synovial fluid analysis, and histopathologic findings that were consistent with sepsis. The addition of 250 mg of PSGAG increased the development of sepsis significantly (P = 0.001), compared with results in control horses. Differences in the development of sepsis between horses injected with methylprednisolone acetate or sodium hyaluronate and control horses were not significant.

Objective-To assess gait abnormalities associated with selective anesthesia of the suprascapular nerve (SSN) achieved by use of perineural catheterization and thereby determine the function of that nerve as it relates to gait in horses. Animals-3 adult horses with no preexisting clinically apparent lameness at a walk. Procedure-Each horse was anesthetized; the right SSN was exposed surgically for placement of a perineural catheter to permit delivery of 1 mL of 2% mepivacaine hydrochloride. Six hours after recovery from anesthesia, each horse was videotaped while walking (50-step data acquisition period) before and after administration of mepivacaine. Videotapes were reviewed and the proportion of abnormal steps before and after selective SSN anesthesia was assessed. A step was considered abnormal if a marked amount of scapulohumeral joint instability (ie, lateral luxation of the proximal portion of the humerus) was observed during the weight-bearing phase of the stride. Results-Clinically apparent gait dysfunction was detected in all 3 horses following perineural administration of the local anesthetic agent. Anesthesia of the SSN resulted in scapulohumeral joint instability as evidenced by consistent lateral excursion of the shoulder region during the weight-bearing phase of gait at a walk. The proportion of abnormal steps before and after SSN anesthesia was significantly different in all 3 horses. Conclusions and Clinical Relevance-These data support the role of the SSN in shoulder joint stability in horses and define SSN dysfunction as 1 mechanism by which the syndrome and gait dysfunction clinically referred to as sweeny may develop.

High molecular weight (MW) hyaluronate (HA) is an integral part of synovial fluid (SF), regulating many important physiologic and pathophysiologic mechanisms. Many of its effects depend on, or are reflected in, the concentration and MW of HA. High-performance liquid chromatography was used to assess simultaneously the concentration and MW of HA in SF obtained from horses with various arthritides: acute traumatic arthritis; chronic traumatic arthritis, including degenerative joint disease (DJD); and infectious arthritis. The size-exclusion column was calibrated, using appropriate HA concentration and MW standards, before the high-performance liquid chromatographic assays of the SF samples. Calibration of the column disclosed that the maximal limit for MW estimation of HA was around 3 million. In control joints, MW of HA ranged from 2 to 3 X 10(6) (mean 2.5 X 10(6)) and did not differ significantly from MW of HA in SF from horses with acute or chronic traumatic arthritis (mean 2 x 10(6); range 1.5 to 3 x 10(6)). Interestingly, a small amount of HA of moderately high MW (approx 1 to 1.5 x 10(6)) was detected in chromatograms of SF from infected joints. This degree of polymerization of SF HA was significantly (P < 0.01) lower, compared with that for control joints. There was no difference in mean (+/- SD) concentration of HA between control joints and joints with acute or chronic traumatic arthritis (0.33 +/- 0.12 g/L vs 0.18 +/- 0.03 g/L or 0.23 +/- 0.12 g/L), indicating that SF HA concentration probably should not be used as a diagnostic marker for the condition. However, the SF HA concentration was significantly (P < 0.01) lower in joints with infectious arthritis (0.07 +/- 0.03 g/L) and in the joints with radiographic evidence of DJD (0.12 +/- 0.01 g/L), compared with control joints.

The antebrachiocarpal and tarsocrural joints of 10 adult horses were randomly assigned to 1 of 4 groups. Groups were formulated and were treated as follows: group 1, control (arthrocentesis only); group 2, buffered lactated Ringer solution; group 3, 10% dimethyl sulfoxide (DMSO; w/v) in lactated Ringer solution; and group 4, 30% DMSO (w/v) in lactated Ringer solution. Joints were lavaged once with the respective solution. Prior to lavage and on days 1, 4, and 8 after lavage, all horses were evaluated for lameness and joint effusion; synovial fluid total and differential WBC counts, synovial fluid total protein concentration, and mucin clot quality were determined. Horses were euthanatized on day 8, and joints were evaluated grossly, histologically, and histochemically. Significant difference was not observed in effect of lactated Ringer solution, 10% DMSO, and 30% DMSO on any measured variable. At 24 hours after treatment, significant (P < 0.05) difference in synovial fluid WBC numbers and total protein concentration was detected between control and treated joints. Eighty percent of lavaged joints had effusion 24 hours after treatment, compared with 30% of control joints. Gross, histopathologic, or histochemical differences were not detected between treated and control joints. Results of the study indicate that buffered lactated Ringer, 10% DMSO, and 30% DMSO solutions induce similar inflammatory changes in articular structures and significantly greater inflammatory reaction than does arthrocentesis alone.

Polysulfated glycosaminoglycan (PSGAG) recently have been reported to potentiate the infectivity of Staphylococcus aureus in horses with experimentally induced septic arthritis. Four groups of 8 horses each had 1 midcarpal joint injected with approximately 33 viable colony-forming units (CFU) of S aureus plus either 1 ml of saline solution (group 1), 250 mg of PSGAG (group 2), 250 mg of PSGAG passed through a 0.6-micrometer filter (group 3), or 250 mg of PSGAG plus 125 mg of amikacin (group 4). Horses that developed clinical signs consistent with sepsis were euthanatized, and samples were collected at necropsy. Horses that survived had samples obtained by use of arthroscopy at days 13 and 14 after injection. Staphylococcus aureus was isolated from 1 group-1 horse, 8 group-2 horses, and 7 of 7 group-3 horses that met protocol, but was not isolated from any group-4 horses. All 16 aforementioned horses had clinical signs, results of synovial fluid analysis, and gross pathologic and synovial membrane histopathologic findings that were consistent with septic arthritis. Polysulfated glycosaminoglycan (250 mg) increased the infectivity of 33 CFU of S aureus (P = 0.001); filtering the PSGAG had no effect. Intra-articular injection of 125 mg of amikacin immediately after inoculating the joint with 33 CFU of S aureus significantly (P = 0.001) decreased potentiation of infection by the PSGAG.