Lameness

• Lameness is a clinical sign, [manifesting] signs of inflammation including pain, or a mechanical defect that results in a gait abnormality. There are five “types” of lameness…

  • Supporting limb (stance phase) lameness
  • Swinging limb lameness
  • Mixed lameness
  • Compensatory lameness
  • Induced/artefactual lameness
• Signalment is important, specific age groups often suffer from specific conditions but it is not exclusive…

  • Foals get haematological septic arthritis, lateral luxation of the patella
  • Young, skeletally immature animals get developmental orthopaedic diseases including OCD, stress related injuries (especially TB horses)
  • Older horses get chronic progressive OA, navicular disease
• A “dropped elbow” indicates failure of the triceps apparatus
• asymmetry is often very important in lameness evaluation

  • Muscle atrophy (disuse or neurogenic)
  • Foot size
  • Fetlock height/angle
  • Localised swelling (synovitis, cellulitis, exostosis/callus formation)
  • Bony asymmetry (e.g. scapular height, tuber coxae/sacrale)
• Palpation should include assessment of…

  • Asymmetry
  • Signs of inflammation
  • Pain (by both deep palpation and induced movement)
  • Loss of function e.g. range of movement
  • Crepitus
  • Peripheral pulses
• • Pressure over the thoracic and cranial lumbar region usually results on lordosis
  • Lordosis = sway back = the spine curve downwards
  • Pressure over the caudal lumbar and sacral region results in kyphosis
  • Kyphosis is a curving Of the spine that causes a bowing or rounding Of the back. Which leads to a hunchback or slouching posture.
• A lameness examination should attempt to assess…

  • Baseline lameness (i.e. before provocative tests) or lameness
  • Attempt to identify multiple limb lameness, and also establish whether these are primary or secondary problems, or if they are artefactual
  • Any lameness identified should be graded and immediately recorded to attempt to create a degree of objectivity
• Alternative/mechanical causes of lameness…

  • “stringhalt” excessive upward flexion of the hindlimb that occurs at walk, this is less obvious at trot and even less so at canter.
  • Fibrotic myopathy
  • Upward fixation of the patella
  • “shivers” syndrome
• for the gait assessment, the horse should be walked at a steady pace away from and towards the observer, observe horses carefully during the turn (be sure to turn on both sides). Careful attention should be placed upon foot placement and gait abnormalities (e.g. “dishing”, “plaiting”). Include lateral observation to assess…

  • Foot flight
  • “tracking up”
  • Cranial and caudal phases of the stride
• With forelimb lameness, identification is based on “Head nodding”. Head elevation begins just before the stance phase of the lamb limb and results in reduced ground reaction force (GRF) due to upward acceleration of the head and neck, and caudal movement of the centre of gravity.

  • Consequently, the horse appears to nod down when the “good” leg is in contact with the ground
• Nodding is done to counterbalance weight, by moving the head up they can limit the peak force through the painful limb.
• For hindlimb lameness, relative excursion of the tuber coxae is generally the accepted visual method of assessment, this is often given terms like hip or pelvic “hike”. The limb with the greater degree of movement is the lame limb, visual cues can be improved by placing tape on each hindlimb running between the tuber coxae and tuber sacrale.

  • Hind limb lameness is harder to appreciate than forelimb lameness
• Hindlimb lameness can mimic forelimb lameness at trot, when the lame limb hits the ground the horse moves it centre of gravity cranially to help unload the limb. The two-beat gait means that there will be a head nod down during the stance phase of the contralateral forelimb, therefore the horse appears to be lame on the ipsilateral forelimb to the lame hindlimb.

  • It should be noted that this is generally apparent only if moderate lameness is present
• Additional assessments include…

  • Sound
  • Excluding all visual clues and listening to syncopation can be extremely useful (remembering the beats of the four standard gaits)
  • Fetlock drop
  • At trot, because there is a higher GRF in the sound (less lame limb) the fetlock will drop further
  • Structural disruption of the suspensory apparatus and flexor tendons will typically result in over-extension of the affected limb at walk
  • Duration of stance phase
  • Lunging exercise
  • Ridden exercise
  • flexion tests
• Flexion tests are not specific to one particular structure

  • Aim to flex the limb to a point slightly before a withdrawal response is elicited
  • There are no clear guidelines as to how long flexion should be applied, most clinicians use 30 to 60 seconds. However, it has been shown that 5 seconds of flexion generally produces similar results to 60 seconds in many cases
• Lunging exercise is helpful in ascertaining whether there might be a bilateral component to lameness

  • Lunging on different surfaces can also be extremely useful
  • Beware of over-interpretation
  • “soft tissue lameness is worse with the limb on the outside/when lunged on soft ground”
  • Very tight circles on hard ground can evoke forelimb lameness of questionable significance, especially in heavier horses
  • Lunging at canter creates a three beat gait
• • Most lameness results from pain during limb loading therefore horses will attempt to reduce the duration of the stance phase
  • This can be especially useful in the assessment of hindlimb lameness during lunging exercise
• Evocative tests includes…

  • Extension tests
  • Direct palpation and pressure
  • Wedge tests
  • These are often overlooked.
  • To perform, the limb should be placed on the block whilst the contralateral limb is held. A wedge can then be placed to evoke lateromedial or dorsopalmar forces
• acepromazine can be useful in calming fractious horses without providing analgesia.
• Kinetics describes motion (e.g. examines the forces applied)
• Kinematics explains motion (e.g. a geometric description of motion without considering causal forces)
• Nerve blocks = perineural anaesthesia
• Nerve blocks are the normal starting point for most lameness. Some cases will have a clear signposting to a specific region (e.g. pain on flexion and joint effusion), which allows to move straight towards imaging of a specific region. However, a large number of cases don’t and we then have to use nerve blocks to pinpoint where the lameness is localised.

  • The most common nerve blocks, are palmar digital, abaxial sesamoid and low 4 point.
• Use a clean technique to avoid introducing infection with nerve blocks. You need to use a sterile technique when you are injecting synovial structures and can be less stringent when injecting around the nerves, however, several of the nerves are very close to synovial structures, so use a sterile technique in case you accidentally puncture another structure.

  • Wash your hands to remove surface debris and either use alcohol or chlorhexidine on the area of injection.
  • You don’t need to clip the leg unless it is very hairy or dirty.
• what drug is most commonly used for nerve blocks?

  Mepivacaine
• Mepivacaine is used for most nerve blocks, it causes less tissue reaction than lignocaine and comes in small bottles so can be opened and used for single procedures.

  • Bupivacaine can be useful where you want a block to last longer (e.g. a horse which has multi limb lameness and you want to block one and work on others, or an uncooperative horse where you have to sedate to block, and then want the block to last until the sedation has worn off).
• you are attempting to perform a nerve block but you get blood, what angle do you direct the needle?


  towards the dorsal aspect
• when placing a needle for a nerve block, at what angle should you place it?


  down the leg
• if you are in the correct place for a nerve block, it will inject easily

  • If it doesn’t you are either not deep enough, and trying to inject intradermally, or too deep and trying to inject into tendon or bone.
  • If you see synovial fluid coming out, remove the needle immediately
• Do not perform nerve blocks if any of the following are present…

  • Suspected fractures or severe soft tissue injuries (such as DDFT ruptures), as the horse will weight bear once the pain is removed and can have catastrophic consequences
  • You can not perform the block in a safe manner
  • Risk of infection, e.g. existing skin disease, such as mud fever, or if the environment / leg cannot be cleaned adequately
  • If the leg has a skin infection, e.g. mud fever or cellulitis, do not inject through this or you will introduce infection deeper.
• What is most common cause of acute onset severe lameness in the horse?

  pus in the foot
• pus in the foot typical presents as shoulder lameness
• What clinical findings would make you suspicious of pus in the foot?

  Hoof tester positive, pounding pulses, focal area of pus
• what view is this?

  dorsolateral palmar medial oblique

  
• Narrow/pinches heels can occur in chronic pain but also the pressure is greater in the region of the navicular bone
• Feet are the most common site of lameness with front feet lameness being much more common than hind. Lameness may be mild and intermittent or more severe, acute or chronic. 1 or more feet can be affected, it is often bilateral in front limbs.
• The hoof removes our ability to detect signs of inflammation as there is often no heat, pain or swelling. However, you can palpate effusion in the distal interphalangeal joint.
• • Assess how the foot lands, this should be flat not heel / toe / side first
  • Landing on the outside wall can lead to inflammation due to the rocking as they land. Horses may walk like this due to pain on the contralateral side to the pain or a hoof imbalance.
• The neurovascular bundle runs down the abaxial sesamoid bones and down on each side of the flexor tendons and into the foot. For the palmar digital nerve block, the needle should place as low as possible (distally) to aid with desensitisation, if you point it towards the hoof the horses reaction will encourage the needle to go in.

  • 1-2ml of mepivacaine

  This is often the first block done in lameness cases
• fill in the blanks regarding the palmar digital nerve block

  A) dorsal

  B) collateral

  C) sole

  D) P3

  E) distal