Con­trol Joint Dis­ease

De­gen­er­a­tive joint dis­ease, or os­teoarthri­tis, is an ir­re­versible con­di­tion, but care­ful man­age­ment of symp­toms will keep your horse mov­ing freely.

Practical Horseman - - Contents - By Les­lie Threlkeld

Learn how to rec­og­nize and man­age de­gen­er­a­tive joint dis­ease as well as how to plan for your horse’s fu­ture.

Did your horse take a funny step or are you just imag­in­ing it? He seems to be work­ing hap­pily and you checked his feet for stones be­fore mount­ing. Yet he does seem to take a lit­tle longer to warm up for work re­cently. Could some­thing be wrong? When your horse comes up lame or even a bit stiff or lack­adaisi­cal un­der sad­dle, count­less dif­fer­ent ail­ments could be the cause. One likely rea­son for lame­ness or a re­luc­tance to work has to do with sore­ness in the joints. Many joints work to­gether to al­low a horse to ac­com­plish daily ac­tiv­i­ties like walk­ing and graz­ing in the field as well as ath­letic feats like jump­ing a cross­coun­try fence or performing a half-pass in the dres­sage arena. When a joint be­comes painful, a horse’s abil­ity to move com­fort­ably is com­pro­mised.

Sim­i­lar to hu­mans, horses may de­velop arthri­tis in their joints that can lead to de­creased mo­bil­ity. Os­teoarthri­tis, also known as de­gen­er­a­tive joint dis­ease, is one of the most com­mon causes of lame­ness. While it cannot be cured, the symp­toms can be con­trolled so your horse can con­tinue to do his job.

How Joints Work

To un­der­stand os­teoarthri­tis, you must first un­der­stand a

joint’s struc­ture and func­tion. In a joint, two or more bones con­nect and al­low move­ment through the har­mo­nious force of mus­cles, ten­dons and lig­a­ments.

The ends of the bones are con­tained in what is called a joint cap­sule, the health of which is ex­tremely im­por­tant to a horse’s abil­ity to move. In the joint cap­sule, a layer of car­ti­lage on the sur­face of each bone pre­vents the bones from painfully grind­ing against one an­other. Synovial fluid, pro­duced by the synovial mem­brane in the joint lin­ing, fills the joint cap­sule to pro­vide ad­di­tional pro­tec­tion and lu­bri­ca­tion.

The joint main­tains healthy func­tion in an ef­fi­cient wear-and-re­pair process that pro­duces synovial fluid and re­pairs dam­aged or aged car­ti­lage cells. How­ever, if the joint is com­pro­mised through in­jury or overuse, the car­ti­lage will wear away, putting more pres­sure on the bones and caus­ing pain and dis­com­fort. It is the com­bined break­down of car­ti­lage and the re­sult­ing sec­ondary changes in the bony struc­tures of the joint cap­sule, such as bone spurs (os­teo­phytes) or sub­chon­dral (bone be­neath car­ti­lage) de­for­ma­tions, that is known as os­teoarthri­tis. Be­cause lost car­ti­lage cannot be re­grown, the dam­age caused by os­teoarthri­tis is ir­re­versible.

Cause and Ef­fect

Joints will nat­u­rally ex­pe­ri­ence wear and tear over time, but there are sev­eral fac­tors that may lead to the de­vel­op­ment of os­teoarthri­tis. Con­for­ma­tion flaws, such as knock knees, up­right pasterns, sickle and cow hocks or ex­tremely straight hind-leg an­gles, may put ab­nor­mal pres­sure on joints. The chances of de­vel­op­ing os­teoarthri­tis also in­crease with age sim­ply due to many years of hard use and the natural de­gen­er­a­tion of the body. An­other pos­si­ble cause of os­teoarthri­tis is a soft-tis­sue in­jury or in­fec­tion that causes in­flam­ma­tion in a joint. How­ever, the sim­plest ex­pla­na­tion for the de­vel­op­ment of os­teoarthri­tis is use. Horses par­tic­i­pat­ing in a high-in­ten­sity ath­letic ca­reer will be more sus­cep­ti­ble due to repet­i­tive use dur­ing train­ing and com­pe­ti­tion.

“It could be chronic cycli­cal forces over an ath­letic ca­reer that cause stress and in­jury to the car­ti­lage, joint cap­sule and syn­ovium,” ex­plains Dane Tatarniuk, DVM, MS, DACVS-LA, a clin­i­cal as­sis­tant pro­fes­sor at Iowa State Univer­sity’s Col­lege of Vet­eri­nary Medicine. Os­teoarthri­tis is more likely to de­velop in hard-work­ing, weight­bear­ing joints, such as the fet­locks, knees, hocks and sti­fles. How quickly os­teoarthri­tis pro­gresses can vary, how­ever. Ma­jor in­juries like a frac­ture or an in­fec­tion can cause the dis­ease to worsen quickly. Tran­sient or short-lived in­flam­ma­tion in a joint will not nec­es­sar­ily cause os­teoarthri­tis, but it could even­tu­ally be a prob­lem if the rea­son of the in­flam­ma­tion is not ad­dressed.

At the cel­lu­lar level, degrada­tive en­zymes most com­monly be­long­ing to the fam­ily called ma­trix met­al­lo­pro­teinases (or MMPs) in­crease with in­flam­ma­tion. “These MMPs, in higher con­cen­tra­tion com­pared to nor­mal joints, lead to ero­sion of the car­ti­lage,” Dr. Tatarniuk says. “As the in­flam­ma­tion per­sists, the body re­sponds by try­ing to sta­bi­lize the in­flamed joint. This is why the joint cap­sule thick­ens, and in­creased min­er­al­iza­tion and bony changes start to progress. The changes to the bone are a slow phys­i­o­log­i­cal re­sponse to the chronic in­flam­ma­tion present.”

Symp­toms of os­teoarthri­tis range from mild to se­vere joint pain and lame­ness. You may also no­tice heat caused by in­flam­ma­tion. In the early stages of the dis-

* Horses par­tic­i­pat­ing in a high-in­ten­sity ath­letic ca­reer will be more sus­cep­ti­ble due to repet­i­tive use dur­ing train­ing and com­pe­ti­tion.

ease, your horse may seem only to have some stiff­ness in his joints after he’s come out of the stall or be­gun a work ses­sion. On the other hand, he may ex­pe­ri­ence vary­ing de­grees of lame­ness or de­creased per­for­mance and a re­luc­tance to work. Call your vet if your horse is sud­denly or in­creas­ingly sore or lame.

Di­ag­nos­ing the Dis­ease

As with any lame­ness in horses, the first step is to find the source of the pain. The vet will be­gin with a phys­i­cal exam and try to nar­row down the ex­act lo­ca­tion of an in­jury. Some signs he or she will look for are ex­cess fluid, heat, de­creased range of mo­tion and pain as­so­ci­ated with flex­ion tests.

“The hall­mark of di­ag­no­sis that ev­ery vet should start with is thor­ough pal­pa­tion and watch­ing the horse move,” Dr. Tatarniuk says. “We try to iden­tify which legs are lame by watch­ing them trot on a straight line or longe line. Flex­ion tests are com­mon to look for an in­crease in sore­ness and give an idea of which area is hurt­ing. From there, we pal­pate the legs thor­oughly from top to bot­tom.”

In some cases, joint ef­fu­sion—in­creased synovial fluid in the joint cap­sule—sec­ondary to in­flam­ma­tion may in­di­cate dis­ease. “Some­times the fluid is nor­mal in a joint, and it’s the vet­eri­nar­ian’s job to de­ter­mine if the joint is truly sore. But if there is fluid and the joint flexes pos­i­tive, there will be strong sus­pi­cion that that is an area of con­cern.”

Once the vet has iden­ti­fied the limb caus­ing a horse’s lame­ness and fur­ther nar­rowed the lo­ca­tion of pain down to a spe­cific area of the leg, it may be nec­es­sary to block nerves with an anal­gesic like li­do­cain to iso­late the pain. If an area is numbed and the horse’s com­fort im­proves and he moves more soundly, then the vet knows there is in­flam­ma­tion or pain in the numbed area. From there, the vet will use ra­dio­graphs to ex­am­ine the bones of the joint. Car­ti­lage dam­age will not show up on a ra­dio­graph, but as the dis­ease pro­gresses, bone spurs (bony growths on the edges of bones that in­di­cate an area of in­creased force on a joint) may be vis­i­ble. The nar­row­ing of a joint space due to car­ti­lage loss may also be vis­i­ble on an ul­tra­sound. Car­ti­lage acts as a sup­port­ive cush­ion and shock ab­sorber be­tween bones. If the car­ti­lage wears away, there is noth­ing sep­a­rat­ing the bones and al­low­ing smooth move­ment of the joint. Se­vere cases of car­ti­lage loss may re­sult in painful bone-on-bone sit­u­a­tions.

“That’s where we might see os­teo­phytes, or spurs, which are bony pro­lif­er­a­tions or ir­reg­u­lar­i­ties as­so­ci­ated with the joint. That gives us an idea of how far the bony changes have pro­gressed. If we see no ab­nor­mal­i­ties on the ra­dio­graphs, but there are clin­i­cal signs of os­teoarthri­tis, it could just be the early stages of the dis­ease,” Dr. Tatarniuk says.

Ul­tra­sounds are typ­i­cally used to di­ag­nose soft-tis­sue in­juries, but they can also be used to eval­u­ate the mar­gins of the joint. Pa­trick Loftin, DVM, MS, a sur­geon at Tryon Equine Hos­pi­tal in Colum­bus, North Carolina ex­plains that when us­ing ul­tra­sounds, “You can’t see through the bone, but you can start to see if a spur is build­ing and is not fully cal­ci­fied. You can also see if there is ex­cess fluid or if the syn­ovium is thick­ened.” An in­flamed synovial mem­brane is known as syn­ovi­tis and may cause pain and swelling of the joint.

It is pos­si­ble to per­form an MRI (mag­netic res­o­nance imag­ing) for fur­ther ex­am­i­na­tion, but this is a very spe­cial­ized and ex­pen­sive pro­ce­dure. Few vet­eri­nary fa­cil­i­ties have MRI ma­chines, and they are rarely used, es­pe­cially to di­ag­nose arthri­tis, which can usu­ally be ac­com­plished through a phys­i­cal exam and se­ries of X-rays.

Os­teoarthri­tis is not al­ways the cause of joint pain. It is pos­si­ble that the col­lat­eral lig­a­ments or other struc­tures of the joint have been in­jured. “It could be 100 dif­fer­ent things and that’s where your phys­i­cal and lame­ness ex­ams come into play,” Dr. Loftin says. “When we talk about arthri­tis in the horse, it seems like the most com­mon thoughts are of the car­ti­lage and bone spurs, but the joint is a full-func­tion­ing struc­ture. There’s car­ti­lage but also un­der­ly­ing bone, synovial lin­ing and joint fluid that all have to work to­gether to make the joint func­tion nor­mally. You have to think about it as an en­tire struc­ture.”

How to Cope With Joint Dis­ease

De­gen­er­a­tive joint dis­ease cannot be cured. “Once it starts you can’t turn back the clock,” Dr. Loftin says. How­ever, you can man­age the symp­toms and po­ten­tially slow the pro­gres­sion of the dis­ease. It is ideal to catch the signs of dis­ease early so that treat­ment can be­gin. The pri­mary goals when treat­ing os­teoarthri­tis are to re­duce in­flam­ma­tion in or­der to slow the degrada­tive process and sub­se­quently pro­vide the horse with some pain re­lief.

Sys­temic anti-in­flam­ma­to­ries or a non­s­teroidal anti-in­flam­ma­tory med­i­ca­tion, such as phenylbu­ta­zone, are typ­i­cally the first step in treat­ment. Some horses are sen­si­tive to tak­ing bute for an ex­tended pe­riod of time and may de­velop stom­ach ul­cers or kid­ney prob­lems. There­fore, bute is an ef­fec­tive treat­ment to soothe acute arthri­tis flare-ups, but firo­coxib (Equioxx ) may be a bet­ter long-term so­lu­tion be­cause it is gen­tler on the stom­ach.

Dr. Loftin says that med­i­ca­tions such as hyaluronate sodium de­liv­ered in­tra­venously (LEG­END ) and poly­sul­fated gly­cosamino­gly­can de­liv­ered in­tra­mus­cu­larly (Ad­e­quan ) have good re­sults as far as full-body care, es­pe­cially for horses who have mul­ti­ple joint prob­lems, and can help in­crease joint func­tion be­fore re­sort­ing to in­tra-ar­tic­u­lar joint in­jec­tions.

In­tra-ar­tic­u­lar joint in­jec­tions, or in­ject­ing the joint, de­liver the medicine straight to the af­fected area rather than treat the whole horse with sys­temic drugs. The most com­mon type of in­jectable med­i­ca­tion are cor­ti­cos­teroids, but Dr. Tatarniuk ex­plains that while they are “very good at re­duc­ing in­flam­ma­tion in a joint, they are a lit­tle ir­ri­tat­ing to the car­ti­lage” over time.

“Stud­ies find that long-term use of steroids, although very good at re­duc­ing in­flam­ma­tion, will in­crease the amount of degrada­tive en­zymes in the joint,” Dr. Tatarniuk says. “The short­term gain of re­duc­ing the in­flam­ma­tion in the joint from the cor­ti­cos­te­riod helps elim­i­nate pain and lame­ness. But long-term or repet­i­tive use cer­tainly does not help the degra­da­tion of the joint al­ready hap­pen­ing from os­teoarthri­tis. How­ever, with arthritic joints, the steroids are very ef­fec­tive at re­duc­ing in­flam­ma­tion and im­prov­ing com­fort, so they still act as a very im­por­tant tool in manag­ing arthri­tis. This ra­tio­nale, though, is why pre­ven­tive joint in­jec­tions with a cor­ti­cos­te­riod in a healthy, non-arthritic joint are not rec­om­mended.

Os­teoarthri­tis of­ten de­vel­ops in a horse’s hard­work­ing, weight-bear­ing joints, such as the fet­locks, knees, hocks and sti­fles. Horses par­tic­i­pat­ing in high-level com­pe­ti­tion are of­ten more prone to this dis­ease due to overuse.

Bone spurs (Os­teo­phytes)

In­flamed joint cap­sule

Early stage: thinned car­ti­lage and blis­ter for­ma­tion Ad­vanced stage: sub­chon­dral bone (bone be­neath car­ti­lage) de­for­ma­tion Sub­chon­dral bone ex­posed De­gen­er­a­tive Joint Dis­ease

Cer­tain con­for­ma­tion flaws, such as knock knees, up­right pasterns, sickle and cow hocks (shown) or very straight hind-leg an­gles, may put un­due stress on joints and could con­trib­ute to os­teoarthri­tis de­vel­op­ment.

In or­der to pro­vide an ac­cu­rate di­ag­no­sis, a vet will typ­i­cally con­duct a lame­ness exam, which in­cludes flex­ion tests of the horse’s joints.

A com­mon os­teoarthri­tis treat­ment op­tion is in­ject­ing the joint di­rectly, which de­liv­ers the medicine straight to the af­fected area.

You can help pre­vent joint is­sues in your horse by mon­i­tor­ing his weight and mak­ing sure he has a reg­u­lar ex­er­cise pro­gram that’s ap­pro­pri­ate for his level of fit­ness.

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