dogs with oa show clinical signs including lameness , increasing immobility , and muscle weakness , which can lead to a reduction in quality of life .
although oa can not be cured , long - term management of the disease can be very rewarding for the veterinarian and pet owner .
managing pain with pain medications is an essential first step , including nonsteroidal anti - inflammatory drugs and chondroprotective drugs .
, physical rehabilitation is a great way to improve mobility and keep dogs active as they age . and
finally there is surgical management , for example , chondrocyte transplantation , arthrodesis , and arthroplasty [ 4 , 5 ] .
rehabilitation protocols in the veterinary field are modeled after those proven to be beneficial in people .
although much research has been published on the use of swimming as physical therapy for humans , there have been few controlled studies on swimming as a treatment protocol for dogs .
however , many reports have shown the advantages of rehabilitation programs for dogs [ 612 ] .
reflect the fact that swimming , walking , and massage are not the only modalities employed in rehabilitation , particularly for oa .
aquatic exercise is suitable for oa patients  dogs and humans as well . the buoyancy , hydrostatic pressure , viscosity , resistance , and surface tension of water increase the efficacy of the exercise .
these properties of water have a positive effect , resulting in increased muscle mass , strength , and endurance , as well as decreased pain during movement [ 14 , 15 ] .
water buoyancy significantly decreases contact force and stress on weight - bearing joints , bones , and muscles , which in turn reduces pain .
due to the lack of effective monitoring methods of joint homeostasis during swimming in oa dogs , this study aimed to determine if swimming could improve the function of oa in canine hip joints .
moreover , two serum biomarkers , chondroitin sulfate epitope wf6 ( cs - wf6 ) and hyaluronan ( ha ) , were used to monitor joint homeostasis during the 8-week swimming program .
a monoclonal antibody cs - wf6 , which recognizes a native epitope in cs chain , and serum ha have been studied as a biomarkers of disease progression , since significantly increased levels were reported in cases of osteoarthritis . for this our hypothesis
is based on that if swimming could improve function of oa joint , clinical signs and biomarker level should improve .
the experimental protocol was approved by the faculty of veterinary medicine and the ethics committee , chiang mai university , thailand .
fifty - five dogs with a body condition score [ 17 , 18 ] between 36 out of 9 , included german shepherd ( n = 3 ) , golden retriever ( n = 12 ) , labrador retriever ( n = 18 ) , beagle ( n = 2 ) , pug ( n = 5 ) , shih tzu ( n = 4 ) , french bulldog ( n = 2 ) , american pit bull terrier ( n = 5 ) , and bangkaew ( n = 4 ) .
twenty - two dogs were in the oa with swimming group ( oa - sw ) , consisting of 9 males and 13 females , 47.62  23.21 months old and 25.52
the healthy with swimming group ( h - sw ) had 18 non - oa dogs consisting of 8 males and 10 females , 48.33  21.26 months old and 26.00  9.14  kg .
the third group , the healthy without swimming group ( h - nsw ) had 15 non - oa dogs consisting of 8 males and 7 females , 38.69  20.73 months old and 19.85  13.20  kg .
the healthy 33 dogs were categorized into swimming group ( h - sw ) and without swimming group ( h - nsw ) using computer program .
dogs with clinical signs of chronic lameness ( more than 1 month ) , stiffness and joint pain , and radiological evidence of oa of the hip were eligible .
dogs were examinated by orthopedic veterinarian to confirm oa , previously entrance to this study .
animals which were grade-4 oa dogs , pregnant , and receiving medication or which had hepatic , cardiovascular , gastrointestinal , or neurological disease were excluded .
dogs with lameness due to lumbosacral instability , infection , immune disease , or fractures and dogs which had previously received drug or dietary supplements for oa treatment were also excluded .
moreover , animals were not allowed to have received nonsteroidal anti - inflammatory drugs ( nsaids ) or chondroprotective drugs for 1 month preexperiment , as well as during the experimental period .
an outdoor pool was used for aquatic exercise , with a water temperature between 3035c .
all dogs were allowed to swim for a total of 8 weeks in order to collect the data .
swimming times were measured each week over a 2  d period . the daily protocol consisted of three cycles of swimming for 20  min followed by a 5  min resting period .
clinical signs , range of motion , and blood collection were performed before starting exercise program and repeated every 2 weeks until week 8 .
two veterinarians recorded the severity of clinical signs and range of motion ( rom ) using goniometer every 2 weeks using an ordinal scoring system ( table 2 ) [ 20 , 21 ] ; all veterinarians were blinded to animal .
radiographs of the hip joints were taken prior to the study and at the end of the study period at week 8 and were interpreted by the two veterinarians using the scoring system described in table 1 [ 21 , 22 ] which blinded as well .
three ml of blood was collected from each dog 's cephalic vein every 2 weeks for evaluation of the level of biomarkers for oa [ 4 , 21 , 23 ] .
efficacy of the treatment was assessed by means of a clinical scoring system [ 20 , 21 ] which assessed a specific animal 's lameness , joint mobility , pain on palpation , weight - bearing , and overall score of clinical condition .
the dogs walked and trotted 12 meters ( 6 meters for evaluate ) , 3 times each , for evaluation of lameness by two veterinarians .
this was followed by palpation of the hip joint for joint mobility and pain evaluation ; the palpation was performed by two veterinarians 30  min apart .
radiographs were taken for each animal , at enrollment and after 8 weeks of treatment , by the same technician using a standard x - ray machine .
ventrodorsal radiographs were obtained with the dog 's hip and leg in the full extension position .
repositioning of the dog for subsequent radiography was guided by the original film , and the same radiographic settings ( i.e. kv , ma and ms ) were used .
all radiographs in a set ( 2 films ) for each dog were evaluated concurrently by two veterinarians using the criteria in table 1 .
only dogs with hip joint oa of grades 13 were used as subjects of this study .
one ml blood samples from each dog were kept in anticoagulant ( 100  iu / ml heparin ) for a complete blood count ( cbc ) .
two ml blood samples were centrifuged at 10,000  g for 15  min to obtain the serum ; this was kept frozen at 20c until blood chemical tests and biomarker assay were performed .
cbcs and blood chemistry tests were conducted at the small animal hospital , faculty of veterinary medicine , chiang mai university , chiang mai , thailand .
the blood samples were analyzed for cbc , including hematocrit and hemoglobin levels , red blood cell count , white blood cell count ( wbc ) , and platelet count .
two ml of serum was analyzed for blood chemicals , including aspartate aminotransferase ( ast ) , alanine aminotransferase ( alt ) , blood urea nitrogen ( bun ) , and creatinine .
elisa ( enzyme - linked immunosorbent assay ) was used as a biomarker assay , following previous studies performed by our research group [ 4 , 21 , 23 , 24 ] at thailand excellence center for tissue engineering , department of biochemistry , faculty of medicine , chiang mai university , chiang mai , thailand .
a quantitative two - step elisa was developed based on the results from an initial study that characterised the epitopes recognized by the monoclonal antibody wf6 .
diluted canine serum samples , 1  :  5 in 6% bsa - te ( bovine serum albumin - tris / edta ) buffer , were added to 1.5  ml plastic tubes containing an equal volume of monoclonal antibody wf6 ( cell culture supernatant , 1  :  200 dilution in te buffer ) .
the standard used was embryonic shark skeletal cartilage aggrecan ( the a1d1 fraction ) at different concentrations ( 1910,000  ng / ml ) in 6% bsa - te buffer .
after incubation at 37c for 1  h , the samples ( or standard ) mixed with wf6 were added to a microtiter plate previously coated with shark skeletal aggrecan ( the a1 fraction ) ( 100  l / well at 10  g / ml ) ; the samples were blocked with 1% bsa .
the plates were incubated at 37c for 1  h , and the wells were then washed with te buffer .
louis mo , usa ) was then added ( 100  l / well ; 1  :  2,000 dilution in te buffer ) .
after incubation at 37c for a further 1  h , the amount of bound peroxidase was determined using opd ( o - phenylenediamine dihydrochloride ) substrate ( sigma - aldrich ) .
an elisa assay was developed for determining hyaluronan ( ha ) in serum , based on previous work with ha - binding proteins .
canine serum samples or standard ha ( healon ) at various concentrations ( 1910,000  ng / ml in 6% bsa - pbs , ph 7.4 ) were mixed with an equal volume of biotinylated habps ( hyaluronan binding proteins ) derived from bovine articular cartilage ( 1  :  200 in 0.05  m tris - hcl buffer , ph 8.6 ) .
after incubation at room temperature for 1  h , the samples ( 100  l ) were added to microplate wells previously coated with human umbilical cord ha ( sigma - aldrich ) ( 100  l / well at 10  g / ml ) ; they were then blocked with 1% bsa ( 150  l / well ) . after further incubation at room temperature for 1  h ,
peroxidase - conjugated anti - biotin antibody ( zymed , south san francisco ca , usa ) ( 1  :  2,000 dilution , 100  l / well in pbs ) was added next .
the plate was incubated at room temperature for a further 1  h , and the bound peroxidase was determined using opd substrate .
nonparametric 2-sample mann - whitney procedure was used to test for differences before and after treatment .
the results of serum cs - wf6 and ha analysis are presented as mean of relative change .
nonparametric 2-sample mann - whitney procedure was also used to test for differences between weeks 0 , 2 , 4 , 6 , and 8 .
relative data were analyzed using the sas version 8.0 software package ; p  0.01 was considered to be significant .
all dogs enrolled in the trial had hemogram and biochemical profile results within the reference range throughout the trial ( data not shown ) .
twenty - two out of 77 dogs withdrew from the study due to various reasons : 10 dogs left because of illness , 5 dogs moved to another province , 2 dogs died from car accidents , and 4 dogs were unable to swim with sufficient frequency .
clinical evaluation of the oa - sw group found that nearly all parameters ( lameness , joint mobility , weight bearing , and overall score ) showed significant improvement ( p < 0.05 ) at week 8 compared to pretreatment , while pain on palpation was significantly improved ( p < 0.05 ) at week 6 ( table 3 ) .
for range of motion ( rom ) evaluation , both extension and flexion of the hip joint were found to be significantly improved ( p < 0.05 ) in the oa - sw and h - sw groups at week 8 compared to pretreatment , while the control group ( h - nsw ) showed no difference ( table 4 ) . all 22 dogs in the oa - sw group had been diagnosed with oa of the hip joint and were classified as grade 1.95  0.67 via a radiographic scoring system . two biomarkers ( cs - wf6 and ha ) were also used to confirm oa by comparing oa and non - oa groups ( figure 1 ) .
the oa group showed significantly ( p < 0.05 ) lower ha ( 31.25  18.52 ) and higher cs - wf6 ( 83.91  35.64 ) levels compared to the non - oa group ( ha = 70.42  27.97 and wf6 = 29.79  24.66 ) .
the relative level of serum cs - wf6 in the oa - sw group was dramatically decreased beginning at week 4 ( 90.52  31.02 ) , but it was found to be significantly different ( p < 0.05 ) compared with preexercise ( 100 ) level at weeks 6 ( 64.44  23.16 ) and 8 ( 40.68  19.71 ) . on the other hand , the relative expression of serum cs - wf6 in the other two groups ( h - sw and h - nsw ) showed no significant change over the 8-week exercise period ( figure 2 ) .
the relative level of serum ha in the oa - sw group increased beginning at week 2 ( 137.50  39.39 ) and then continued to rise steadily : at week 4 , 166.60  69.09 ; week 6 , 257.75  94.83 ; and at the end of week 8 , 470.88  286.96 .
moreover , the levels of serum ha of the h - sw group were significantly ( p < 0.05 ) higher than preexercise level : at week 2 , 169.44  102.44 ; week 4 , 165.06  55.87 ; week 6 , 164.39  75.28 ; and at the end of week 8 , 164.39  29.68 ( figure 3 ) .
first , because this was a clinical study the animals could not be controlled by using the same breed , sex , and/or age . moreover , not all dogs in the study had the same oa grade . however , we tried to maximize the number of animals ( 22 ) included in the oa with swimming group .
this is because all dogs in this study were pets with oa hip problems and had been brought to a small animal hospital by their concerned owners ; for ethical reasons , it was felt that these animals should not be deprived of treatment to relieve pain .
third , since this study used an outdoor swimming pool , we were unable to do a long - term study ( 4 to 6 months or more ) because the rainy season in the north of thailand would overlap with the study period .
some animals swam for longer than 2 months , but only a small number which was insufficient for statistical analysis .
so we established a 2-month cutoff period for studying the effects of the swimming program .
( however , we have recently constructed an indoor swimming pool for future studies on the long - term effects of swimming on oa dogs . )
fourth , the total number of animals in this study was not large , particularly because many dogs ( n = 22 ) withdrew from the study due to various problems : illness ( 10 dogs ) , moving out of the study area ( 5 ) , death ( 2 ) , and inability to swim frequently ( 12 ) .
another possible limitation of the study is that we measured only the hip and no other joints .
human studies have found that water temperature is another factor affecting physiology during aquatic exercise , for example , heart rate or blood pressure .
previous human studies showed higher heart rates during swimming in water with a temperature of 33c versus 27c or lower [ 25 , 26 ] .
although there are no existing reports on the effect of water temperature on canine physiology during swimming , our study was performed in water with a temperature between 3035c to avoid this effect of water temperature .
another limitation in this study is that we did not have a force plate analysis instrument .
evaluation of clinical signs and range of motion of the hip joint were performed by two veterinarians via blind technique .
our trial found that the swimming program had a slow effect on clinical signs ( lameness , joint mobility , weight bearing , and overall score ) , with improvement at week 8 ; only the pain on palpation score showed significant improvement earlier , at week 6 .
to evaluate the motion of the hip joint , passive rom was measured every 2 weeks by two independent veterinarians .
swimming was found to improve the rom of the hip joint not only in oa dogs but also in healthy dogs as well , with a significant improvement shown at week 8 .
however , some research reports have had a different result . in 2003 ,   reported no significant effect of a 20-week aquatic training program on children with juvenile idiopathic arthritis . but that research had several limitations , for example , a limited number of patients , low intensity and frequency of exercise , and in - home assessment .
another advantage of swimming , from a recent study using a mouse model , is increased muscle mass , function and metabolic profile . based on the present results
, it can be concluded that swimming 2 to 3 times per week for 8 weeks continuously can improve the rom of the hip joint by about 5% , not only in oa dogs but also in normal dogs as well .
a human study found that aquatic exercise for 6 weeks can improve the rom of the hip joint by 10.9% .
a study comparing the therapeutic benefits of treadmill walking and swimming found that dogs that swam had significantly greater stifle rom compared with dogs that exercised by walking on a treadmill .
moreover , we used radiographic images to compare the pathology of oa joints between pre- and postexercise .
radiographic findings between weeks 0 and 8 in the oa - sw group showed no significant change .
however , radiographic images can not provide as much information as an mri or ct , but we did not have these facilities for animal use at our institute .
when the levels of serum biomarkers were compared between the oa and non - oa groups , a significantly lower level of serum ha and a higher level of serum cs - wf6 were found in oa dogs compared with non - oa dogs .
this result was similar to our previous study on dogs with hip dysplasia , which showed that the serum levels of cs - wf6 increased , while ha levels decreased . taken together with other reports [ 4 , 21 ] , this demonstrates the usefulness of these biomarkers to predict the progress of oa .
an increase in the wf6 epitope may reflect a catabolic response , while a decrease may reflect a blockage of the catabolic pathways ; this may be helpful for the diagnosis or prognosis of disease .
the ha concentration in the joint fluid and serum of animals with diseased joints has been reported to be lower than normal because of a decrease in the synthesis mechanism via synoviocytes and chondrocytes [ 23 , 32 ] .
hip joints are diarthrodial joints , which are freely moveable joints containing synovial fluid within a connective tissue joint capsule that allows for low - friction and low - wear articulation of the cartilaginous ends of long bones .
joint movement is very important for homeostasis in the joint environment because it helps articular cartilage absorb synovial fluid . in oa animals ,
joint movement is restricted because of pain , which in turn decreases the absorption of synovial fluid by articular cartilage .
this will lead to decreased nutrients and an accumulation of waste products in cartilage . shortly after exercise ,
an elevation of serum levels of cartilage oligomeric matrix protein ( comp ) was found in patients with oa , suggesting an effect on cartilage metabolism .
a recent study found an exercise - induced increase in interleukin-10 levels in the ( peri-)synovial fluid of patients with knee oa , to which anti - inflammatory and chondroprotective properties are ascribed .
a novel monoclonal antibody , wf6 , which recognizes an epitope in native cs chains , was decreased after swimming .
the finding of decreased levels of serum cs - wf6 after exercise reflects an alteration in the metabolism of the cartilage . in chronic oa , the level of cs - wf6 is higher than normal because the native cs chain in cartilage is degraded and released into the blood stream [ 23 , 24 ] .
the decrease of cs - wf6 in this study indicated that swimming could increase the anabolism and decrease the catabolism in oa joints .
it is also possible that swimming could increase the blood supply to the joint , thus increasing the metabolism in cartilage and surrounding tissue .
this is supported by the serum ha results in the present study ; ha levels increased in both swimming groups , but to a greater extent in oa dogs than in normal dogs .
although ha is widely distributed throughout the body ( umbilical cord , nasal cartilage , vitreum , cutis , and lymph nodes in the thorax ) , the highest concentration is found in synovial fluid and also in connective tissue such as the synovial membrane .
our results found that , after 8 weeks of a swimming regimen , the rate of ha synthesis was higher in oa dogs than in normal dogs .
it is possible that swimming induced ha synthesis by synoviocytes and chondrocytes from increased blood supply to the joint . in human studies , blood flow during maximal exercise
compared to resting conditions has been found to increase up to 20-fold on average , and in predominantly white muscles increases up to 80-fold have been reported .
one disadvantage of this study was that we could not measure biomarker levels in synovial fluid during swimming , which could provide useful information for further research , for example , on the levels of other serum biomarkers or gene expression . in conclusion
, the present study demonstrates that it is possible to evaluate the effects of exercise on articular cartilage .
we discovered a significant change in serum biomarker levels in the group that performed swimming compared to the nonswimming group .
swimming appears to be a useful strategy for regaining movement and function in with oa joint .
 this study aimed to determine whether swimming could improve function of osteoarthritic joints in canine hip oa . 
 fifty - five dogs were categorized into three groups . the oa with swimming group ( oa - sw ; n = 22 ) , the healthy ( non - oa ; n = 18 ) with swimming group ( h - sw ) , and the healthy ( non - oa ; n = 15 ) without swimming group ( h - nsw ) . 
 all animals were allowed to swim for a total of 8 weeks ( 2-day period , 3 cycles of swimming for 20 minutes , and resting period for 5 minutes in each cycle ) . 
 three ml of blood was collected every 2 weeks for evaluation of the levels of biomarkers for oa , including chondroitin sulfate epitope wf6 ( cs - wf6 ) and hyaluronan ( ha ) . 
 clinical evaluation of the oa - sw group found that most parameters showed improvement ( p < 0.01 ) at week 8 compared to pretreatment , while pain on palpation was improved ( p < 0.01 ) at week 6 . 
 the relative level of serum cs - wf6 in the oa - sw group was found to be significantly different ( p < 0.01 ) at weeks 6 and 8 compared with the preexercise . 
 the levels of serum ha of the h - sw group in weeks 28 were significantly ( p < 0.01 ) higher than preexercise . 
 conclusion , swimming over 2-day period , 8 weeks continually , can improve the function of oa joint . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion