Vet clinic Are flex­ion tests a fair judge of sound­ness?

Flex­ion tests can of­fer clues about a horse’s sound­ness, so why are they so con­tro­ver­sial? An­drea Oakes in­ves­ti­gates

Horse & Hound - - News Insider -

THERE’S a par­tic­u­lar point in the pre-pur­chase ex­am­i­na­tion (PPE) where both buyer and seller wait with bated breath.

Af­ter a short pe­riod with one leg held aloft, will the horse trot away sound — or will he show any signs of lame­ness?

The flex­ion test has long had its crit­ics, but it re­mains a valu­able part of both the PPE and lame­ness in­ves­ti­ga­tion. “This is a com­mon pro­ce­dure that can be car­ried out in both fore- and hindlimbs,” ex­plains Hetty Hill MRCVS, who works along­side Dr An­dre Buthe at his sport horse clinic in Marl­bor­ough, Wilt­shire. “The process in­volves man­u­ally flex­ing a horse’s leg for a pe­riod of time be­fore re­leas­ing it and watch­ing him trot away im­me­di­ately af­ter­wards. The idea is to stress the joints and sur­round­ing soft tis­sue struc­tures (the lig­a­ments and ten­dons), to as­sess the horse for any de­te­ri­o­ra­tion in sound­ness.

“The horse is trot­ted in a straight line be­fore and af­ter flex­ion is per­formed, and so the same sur­face must be used to al­low for the most ac­cu­rate com­par­i­son,” she adds.

The BEVA (Bri­tish Equine Ve­teri­nary As­so­ci­a­tion) and RCVS (Royal Col­lege of Ve­teri­nary Sur­geons) PPE guid­ance notes state that flex­ion tests of all four limbs may be car­ried out if the ex­am­in­ing ve­teri­nary sur­geon con­sid­ers it safe and ap­pro­pri­ate to do so. While most vets elect to per­form flex­ions on most horses to gain ad­di­tional in­for­ma­tion to form an opin­ion on the suit­abil­ity of a prospec­tive pur­chase, there are oc­ca­sions when the tests are short­ened or aban­doned.

“Flex­ion may not be pos­si­ble with a young or poorly han­dled horse, or where there are no suitable fa­cil­i­ties,” says Hetty. “We are obliged to record all rel­e­vant find­ings on the PPE cer­tifi­cate. If flex­ion tests are omit­ted, the vet should doc­u­ment why.”


“WHEN the horse trots af­ter flex­ion, the vet will as­sess any changes in gait be­fore grad­ing the re­sponse,” ex­plains Hetty. “The first con­sid­er­a­tion is whether there is lame­ness, or, in the case

of an in­ves­ti­ga­tion rather than a PPE, any wors­en­ing of pre­vi­ous lame­ness. The de­gree of lame­ness is then graded.”

A pos­i­tive flex­ion test gen­er­ally refers to lame­ness that per­sists for a num­ber of strides — usu­ally more than three to five. Con­fu­sion can arise among own­ers, how­ever, for two rea­sons: the way tests are car­ried out and the in­ter­pre­ta­tion of the re­sults. Can re­sponse dif­fer de­pend­ing on the force and an­gle used when flex­ing the leg, for ex­am­ple, or the du­ra­tion?

“Re­search has shown that in­creased force ap­plied and time spent in flex­ion am­pli­fies the horse’s re­sponse, and that a horse’s age and work­load may in­flu­ence re­sults,” says Hetty. “Although most vets will hold the limb for between 30 sec­onds and a minute, there is no agreed time for flex­ion. Nei­ther are there any de­fin­i­tive guide­lines as to how many strides of lame­ness rep­re­sents a pos­i­tive re­sult. This is as­sessed sub­jec­tively by the vet.

“The in­ter­pre­ta­tion of the re­sponse to flex­ion may vary slightly between vets, but this is not a prob­lem pro­vided each in­di­vid­ual is con­sis­tent in his or her ap­proach.”

Hetty ex­plains that there have been var­i­ous sug­ges­tions as to how the flex­ion test method can be reg­u­lated.

“A group of vets from Italy pub­lished a study in 2016 where they used a pres­sure-sen­si­tive glove to stan­dard­ise the force ap­plied dur­ing lower limb flex­ions,” she says. “This has some po­ten­tial to min­imise one of the vari­ables in per­form­ing the test, but it does not elim­i­nate oth­ers — such as the sub­jec­tive na­ture of the vet’s eval­u­a­tion of a re­sponse to flex­ion.

“Equine gait anal­y­sis sys­tems us­ing mo­tion sen­sors are also be­com­ing more widely used in the UK,” adds Hetty. “If used ap­pro­pri­ately, they can pro­vide a means for eval­u­at­ing lame­ness ob­jec­tively and may be used in record­ing re­sponse to flex­ion or nerve blocks dur­ing a lame­ness work-up. These sys­tems may be used more com­monly in PPEs in the fu­ture.”


WHILE there is lit­tle ev­i­dence cur­rently avail­able to link a pos­i­tive flex­ion test with fu­ture lame­ness, var­i­ous stud­ies have tried to bring sci­ence to this rather non-spe­cific pro­ce­dure.

De­spite their short­com­ings, flex­ion tests can be a use­ful “red flag”. The fact that one fore­limb re­sponds dif­fer­ently to the op­po­site one, when tested in the same way, could in­di­cate a prob­lem — but where, ex­actly?

“When flex­ing the fet­lock, for ex­am­ple, the joint it­self is put un­der pres­sure — but so are nu­mer­ous soft tis­sue struc­tures in­clud­ing the sus­pen­sory lig­a­ment branches, the flexor ten­dons and the prox­i­mal sesamoidean lig­a­ments,” says Hetty. “Is­sues with any of these ar­eas may con­trib­ute to re­sult­ing changes in gait.

“It is not straight­for­ward to iso­late spe­cific anatom­i­cal ar­eas with ac­cu­racy when per­form­ing a flex­ion test. This is par­tic­u­larly true in the hind limb, where the re­cip­ro­cal ap­pa­ra­tus en­sures that the sti­fle and hock move to­gether.

“It is fair to say, how­ever, that flex­ion tests play an im­por­tant part in a lame­ness eval­u­a­tion — but only if in­ter­preted along­side other find­ings,” she adds. “Flex­ion can be use­ful in ex­ac­er­bat­ing low-grade lame­ness to aid your vet in a lame­ness work-up, and may give an in­di­ca­tion of where to start with di­ag­nos­tic nerve blocks. But the test is just one piece of the puz­zle, so the horse’s re­sponse must be in­ter­preted in light of other find­ings.

“The way a horse moves or flexes may give your vet ideas about where the prob­lem could be, but flex­ion tests alone can­not pro­vide a di­ag­no­sis,” says Hetty. “They are not a sub­sti­tute for other com­po­nents of an orthopaedic exam, such as man­ual pal­pa­tion of the limbs, dy­namic gait anal­y­sis, nerve blocks and di­ag­nos­tic imag­ing tech­niques.

“Flex­ion tests have a place in the PPE and in orthopaedic as­sess­ments, but their lim­i­ta­tions must be un­der­stood and ac­knowl­edged,” she con­cludes.

“Don’t be afraid to ask your vet to ex­plain their find­ings and to give their opin­ion of how rel­e­vant they think these are for you and your horse.”

A flex­ion test should be done in con­junc­tion with a lame­ness work-up or a pre-pur­chase ex­am­i­na­tion to as­sess the horse’s sound­ness

De­spite their bad press, flex­ion tests, in which thelimb is flexed to stress joints and sur­round­ing softtis­sue to show po­ten­tial is­sues, are a valu­able part of a vet’s lame­ness work-up

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