Lamness examination procedure

A systematic investigation of a lame horse may be time consuming when the cause is not obvious. The examination benefits from standardized facilities such as a level, firm, nonslip surface for walking and trotting the horse and a soft support area for lungeing and riding the lame horse. The examiner must be knowledgeable in equine anatomy, normal conformation and gaits, regional anesthesia, and imaging techniques and be able to recognize forelimb and hindlimb lameness.

The examination begins with a comprehensive medical history; type, age, and training regimen may give important clues to the lameness as will the time since onset of lameness and interim management. The interval since the last shoeing should be noted, as well as any suggestions that the lameness may improve with either rest or exercise. Response to anti-inflammatory or analgesic medications may provide useful information. Results of hematologic and biochemical analyses may shed light on other problems that influence overall performance.

Visual

• First, visualize the animal at rest and from a distance.  Often this can be done while the owner is giving you a history.  Note the body type and condition, conformation, any shifting in weight or abnormal stances, and the attitude of the animal.
• Second, do a closer visual examination of the animal.  Look for abnormal wear in the feet, hoof cracks, lacerations, swellings in joints or tendons, atrophy or swelling of the muscles, and any other gross changes.
• Third, one must observe the animal during exercise, at the walk, trot, and sometimes at the canter or gallop.  Often, the trot is the most advantageous gait for the exam because of its symmetry.  It can be easiest to look at one set of limbs at a time, usually beginning with the forelimbs.  Try to define which limbs are involved in the lameness, and the degree of lameness.   This examination includes watching the horse move from the front, the side and from behind.  Also, circling the horse or having them perform figure eight's can accentuate a lameness.  Look for head nodding, gait deficits, alterations in the height of the foot flight arc, phase of stride, joint flexion angle, foot placement, and symmetry in gluteal rise and duration.  Be aware that during these examinations, choosing the correct surface is important (i.e. hard surfaces for audible interpretations or gravel surfaces to exaggerate certain lameness'), as well as giving the animal enough room to move freely with the handler. 
• With a forelimb lameness, the head will drop when the sound foot hits the ground and rise when weight is put on the lame leg.   This is logical because the animal is attempting to minimize the stress and weight put on the affected limb.     With a hindlimb lameness, the arc of the foot flight is often reduced.  The pelvis will rise just as the lame foot hits the ground.  If the lameness is severe enough, there will be a head nod down on the contralateral forelimb as the pelvis rises.  Also, in a lame horse's gait, often there are various forms of abnormal limb contact during exercise.
• Finally, one can flex or stress different regions of the the legs to try and accentuate a lameness. 

Palpation and Manipulation

• Foot   

            Note the size and shape of the foot.  Compare the normal with the abnormal.  Look for any abnormal hoof wear, ring formation, heel bulb contraction, hoof wall cracks and swellings, and any other asymmetries.  Palpate the coronary band for heat, swelling and pain on pressure.  Have available a hoof pick, a hoof knife and hoof testers.  Clean out the sole of the foot and search for any abnormalities, including frog atrophy, flat -footedness, or puncture wounds.  Use hoof testers on the entire sole and frog region of the foot.  Try to localize any hoof sensitivity or signs of laminitis.                      

• Pastern  

            Palpate this region for heat and or enlargement.  Compare any suspected abnormalities with the opposite pastern. Check for any thickening of the tendons.  Rotate the joint to test for pain in the collateral ligaments.

• Fetlock   

            Palpate both the dorsal and palmar aspect for any thickening and swelling of the joint capsule.   Palpate the superficial and deep digital flexors for heat, pain or swelling.   Palpate the sesamoid bones and the associated ligaments.  Rotate and flex the fetlock to check the collateral ligaments and range of motion.

• Metacarpus/tarsus

            Palpate the tendons on both the dorsal and palmar surfaces for any swelling, pain or heat.   Also, palpate the length of MC3/MT3 and the splint bones looking for abnormalities.  With the fetlock flexed and raised, check the suspensory ligaments and compare them to the opposite side.

• Carpus

            Visualize for swelling on the dorsal and palmar surfaces.  Try to associate any swelling with a particular joint spaces.  Is the swelling diffuse or local?  Palpate all the regions individually.  This evaluation is most affective while the carpus is flexed.   Also, note the degree of flexion and any associated pain.  Evaluate the individual carpal bones and accessory carpal bone with thumb pressure.

• Antebrachium (Forearm)

            Evaluate all the soft tissues for any swelling and inflammation.  Also, palpate the bones of the region (i.e. radius) for any fractures.

• Elbow 

            Palpate the soft tissues of the elbow joint.  One can use a stethoscope to auscult for any crepitation.  Abduct the elbow and carpus to place stress on the medial support structures looking for pain.  Flex and extend the elbow.  Palpate the olecranon, collateral ligaments, and distal humerus.

• Shoulder

              Palpate all the soft tissue of the scapulohumeral joint and look for atrophy or swelling.   Palpate the bicipital bursa region.  Flex, extend, abduct and adduct the shoulder looking for abnormalities.  Look for any atrophy in the region of the scapula.

• Tarsus       

                Evaluate the tarsocrural/tibiotarsal joint for any distension, thickening of the joint capsule, bone proliferation of the distal tarsal joints, distension of the tarsal sheath, inflammation or luxation of any ligaments, or any other abnormalities.  Also, look at the distal intertarsal and tarsometatarsal joints.  Do a hock flexion test (spavin test) where the metatarsus becomes approximately parallel to the ground.    A change in degree of lameness or gluteal rise would indicate a positive result.  Also, while in that region, observe the tibia for any swelling or pain.

• Stifle

            Appreciate any changes in the femoropatellar joint or distension of the joint.  Observe the associated muscles for atrophy or swelling.  Palpate the patellar ligaments.   Note the location of the patella itself, looking for any luxation.  Manipulate the stifle with a patellar displacement test (pushing the patella upwards and outwards in an attempt to engage the medial patellar ligament over the medial trochlea), a cruciate test (evaluating any abnormal craniad or caudad movement of the tibia), and an evaluation of the medial collateral ligament by trying to abduct the limb.

• Femur and Hip

               Examine the muscles of the region for inflammation and/or  atrophy.  Check the femoral artery for the quality of pulsation.  Put pressure on the greater trochanter to check the trochanteric bursa for inflammation. Palpate the femur looking for fractures.   Examine the hip for asymmetry and muscle atrophy.  Measure the distance from the tuber ischiadicum to the greater trochanter, and the tuber sacrale to the greater trochanter.  With any luxation of the hip there may be disparity in these measurements.  Flex and auscult for crepitation.
            

Diagnostic Anesthesia 

            Using appropriate nerve blocks can help localize the causative area of the lameness.  To determine the specific area, begin with a block at the lowest point of the affected limb.  Remember, you DESENSITIZE everything below your nerve block, so it is safest to start distally.  One can choose either an intraarticular(into a joint) or perineural(around a nerve) nerve block.  After the nerve block, the patient is reevaluated for any changes in condition.  When alleviation of lameness is achieved, one can proceed with a diagnostic imaging of the appropriate region.
            A palmar digital nerve block is at the level of the pastern joint or below.  It blocks the palmar/plantar and distal parts of the hoof, PIII, termination of the deep digital flexor and most of the coffin joint.
            An abaxial sesamoid block occurs on the abaxial surface of the base of the proximal sesamoids.   It blocks the entire digit distal to the fetlock, except some areas of skin.
            A low palmar/plantar (or distal metacarpal) block is at the level of the distal ends of the metacarpal bones.  It blocks the fetlock joint, sesamoids, and sesamoid ligaments.
            A high palmar/plantar (or proximal metacarpal) block is at the level of the proximal metacarpal region, just distal to the carpus/tarsus.  It blocks the entire digit and most of the palmar/plantar side of the metacarpal bones.
            A peroneal and tibial nerve block is proximal to the hock.   The injection site for the tibial nerve is about 10cm proximal to the top of the tuber calcis on the medial aspect, and about 10cm proximal to the lateral malleolus for the superficial and deep peroneal nerves.  It blocks deep sensation from the hock and structures distal to it.   Some skin sensation may remain.
    Intraarticular blocks can be performed on most joints at any point during the lameness examination and will be specific to the joint.