EQM400 Lameness Evaluation

• Study notes for Lameness Evaluation, EQM400, 2025 edition by Dr. E Hollenbach

Learning Outcomes

• Demonstrate knowledge of distal limb anatomy
• Perform a basic lameness exam and understand investigation tests
• Recognize and define lameness origins
• Develop a diagnostic approach
• Recognize gait deficits like stringhalt, Sweeney, radial nerve paralysis, upward patellar fixation, and flexural deformities
• Perform diagnostic nerve blocks (palmar digital, abaxial sesamoid, low/high 4/6-point, wheat nerve block, DBLPN) to identify lameness
• Demonstrate arthrocentesis knowledge for common sites (coffin, fetlock, carpus, tarsus)

Introduction

• Lameness is any condition impairing limb or axial skeleton function/structure, visible at rest or in motion
• Causes include trauma, congenital/acquired abnormalities, developmental issues, infections, metabolic conditions, circulatory/nerve disorders, or combinations
• Accurate diagnosis requires thorough understanding of equine anatomy, biomechanics, and body forces
• Differentiating pain-related, mechanical, and neurologic gait abnormalities is crucial
• Pain-induced lameness is the most common
• Lameness examination objectives:
• Determine if the horse is lame
• Identify involved limb(s)
• Locate problem site(s)
• Determine the specific cause
• Select appropriate treatment
• Predict recovery prognosis
• Routine lameness examination steps:
• Complete history (signalment/use)
• Visual exam at rest (hands off)
• Musculoskeletal system palpation (hands on)
• Motion observation
• Observation under work/saddle (if needed)
• Manipulation tests (flexion tests)
• Diagnostic anesthesia
• Diagnostic imaging
• Static examination (hands on/off) precedes exercise
• Diagnostic anesthesia/imaging follow to identify pain location, specific cause, injury extent, and recovery prognosis

Adaptive Strategies

• Horses adapt to lameness with compensatory body movements, with most attempting to "unload" the lame limb
• Chronic lameness causes higher vertical loads on the non-lame limb, resulting in a flatter foot
• Consistent compensatory movements include head displacement (forelimb lameness) and sacrum/tuber coxae displacement (hindlimb lameness)
• Overlap can occur but is typical in moderate to severe lameness

Classification

• Primary lameness contributes most to gait abnormalities
• Compensatory/secondary lameness results from overloading other limbs
• Lameness classified by occurrence within the stride:
• Supporting limb lameness occurs during weight-bearing (stance phase), caused by bone, joint, or soft tissue injuries
• Swinging limb lameness is noticeable in motion, affecting upper limbs or axial skeleton
• Mixed lameness is evident in both swing and stance phases, involving any structure combination
• Primary lameness is the most noticeable before tests, with the most severe being typically assessed first
• Compensatory lameness occurs due to uneven weight distribution from pain, frequently observed as forelimb lameness causing opposite forelimb issues
• Hindlimb lameness can mimic forelimb lameness on the same side and/or cause compensatory on opposite side
• Even minor weight-bearing shifts trigger compensatory lameness, especially at high speeds or long distances, commonly affecting feet, suspensory ligaments, sesamoid bones, hocks, and flexor tendons
• Compensatory within the same limb can occur when healthy structures protect a painful region, such as a horse with navicular toe-first landing

Other Factors

• Most lameness is in the forelimbs: bearing 60-65% of the horse's weight (70% w/rider) and absorbing more shock
• Hindlimbs propel but carry less weight/experience less concussion
• Activity matters: dressage, cutting, and reining strain hindquarters, and will cause more hindlimb lameness
• ~95% of forelimb lameness originates distal to the carpus, so examine the distal limb before assuming issues are in the upper limb
• ~80% of hindlimb lameness involves the hock/stifle; assess the foot/lower limb before these regions
• Other contributing factors: improper shoeing, unsuitable footing, and performance-related muscle fatigue
• Young horses are prone to lameness because their musculoskeletal systems are still developing
• Young horses may be raced or shown, therefore experience injuries that would typically be less likely in older horses

History and Hands-Off Examination:

• Patient age and use are important considerations

Signalment and Use

• Aged pleasure riding horses are prone to problems associated with the forefeet, low-motion joints and ligaments
• Young racehorses have lameness problems with high-motion joints, sprain/strain of flexor support structures, and stress-related fractures
• Competitive trail or endurance riding horses often sustain sprain/strain injuries, tendonitis, and phalange fractures
• Young horses starting traing can become lame from developmental orthopaedic-related problems.
• Common injuries in specific disciplines:¹
  • TB racehorse (Fatigue-associated repetitive overuse)
    • foot bruising
    • quarter cracks
    • heel pain
    • Forelimb fetlock synovitis and fractures
    • Carpal synovitis and fractures
    • Bucked shins in young horses
    • Fatigue/stress fractures (MC/MT, P1, humerus, tibia, pelvis)
    • SDFT tendonitis
    • Suspensory injuries
    • Catastrophic fractures (PSB, P1, MC/MT, and humerus)
    • Palmar/plantar osteochondral disease (POD)
  • Endurance horse
    • Muscle disorders including tying-up and muscle spasm, cramps, and strains
    • Forelimb and hindlimb suspensory desmitis
    • Foot bruising, P3 osteitis, and laminitis
    • Fetlock synovitis/OA
    • SDFT tendonitis
  • Show/pleasure horse
    • Navicular syndrome/disease
    • Coffin joint synovitis/OA
    • Forelimb and hindlimb PSD
    • Distal tarsitis or bone spavin
    • Lumbar and sacroiliac problems
  • Western performance horses
    • Navicular syndrome/disease including DDFT injuries
    • Phalangeal fractures (primarily P2)
    • Pastern ringbone
    • Fetlock and carpal synovitis/OA
    • Distal tarsitis or bone spavin Stifle synovitis/OA
  • Forelimb and hindlimb PSD
  • Thoracolumbar myositis
  • Hindlimb muscle strains
  • Jumping/dressage/eventing
    • Navicular syndrome/disease including DDFT injuries
    • Suspensory branch injuries
    • Forelimb and hindlimb PSD
    • Fetlock synovitis/OA
    • SDFT tendonitis
    • Distal tarsitis or bone spavin
    • Stifle injuries
    • Thoracolumbar myositis—back problems
    • Sacroiliac problems
  • Draft horses
    • Hoof cracks and laminitis
    • Subsolar abscesses, canker, and thrush Ringbone
    • Sweeny
    • Bone and bog spavin
    • Stifle synovitis/OA
    • PSSM
  • Gaited horses (Hindlimb>Forelimb)
    • Distal tarsitis or bone spavin
    • Stifle synovitis/OA
    • Thoracolumbar myositis/back problems
    • DSLD

History

• Records including the lameness's duration/intensity, specific symptoms, preceding activity, and previous treatments/therapies
  • What activity does the horse perform and did the lameness occur during this activity?
  • How long has the horse been lame? (Acute vs. chronic injury.)
  • Has the horse been rested or exercised during the lameness period? (The horse may not exhibit the same lameness if it has been rested.)
  • Has the lameness worsened, stayed the same, or improved? (May indicate severity of the problem.)
  • Was the cause of the lameness observed? (This should include the character of the lameness at the onset.)
  • Does the horse warm up out of the lameness?
  • When do you notice the lameness most consistently?
  • What treatments have been given, and have they helped? (Response to treatment may help predict the prognosis or may mask the severity of the current lameness)
    • When was the horse last shod or trimmed?
    • What are the abnormalities that the owner or trainer observe or feel when they ride the horse or watch the horse go?

Hands Off Examination

• Visual assessment while the horse stands squarely on a level surface
• Begin from a distance, viewing from multiple angles, and move in for closer inspection
• Assess body type, conformation, body condition, posture changes, weight distribution, and limb positioning
• Any asymmetry or alterations in limb contours need noting
• Forelimbs should bear weight evenly and be opposite each other
• Weight shifting between limbs or extending forelimbs forward may indicate bilateral forelimb discomfort
• Resting one hindlimb consistently or being unable to bear weight indicates lameness
• Any minor stance changes are a potential issue and should be investigated further
• Close inspection for symmetry comparison
• Hooves should be checked for wear, cracks, imbalance, size differences, or contraction
• Joints, tendons, and sheaths should be checked for swelling
• Muscles of limbs, back, and pelvis assessed for atrophy or enlargement
• Comparing left and right sides can detect subtle abnormalities
• Narrower hoof with higher heel and extensor muscle atrophy indicate lameness (especially chronic/bilateral)
• Hindlimb atrophy of middle gluteal/gracilis suggests an underlying problem
• An uneven tuber sacrale/pelvic tilt often corresponds to asymmetric gait pattern, to be evaluated further

Conformation

• Conformation is how a horse is shaped by bones and muscles
• Often assessed subjectively based on breed standards/discipline-specific ideals; "normal" conformation varies
• Some conformational traits increase lameness risk
• Distinguishing which abnormalities contribute to lameness improves understanding of the causes
• Structured conformation evaluation is systematic, focusing on:
• Head/neck
• Forelimbs
• Trunk
• Hindlimbs
• Evaluate each equally; examine specific conformational traits in detail after initial assessment
• Begin with a side profile, assessing balance between forehand and hindquarters
• Observe topline curvature/proportions from poll to gaskin
• Pay attention to how limbs attach, long bone lengths, and wither heights correlate to maintain proportionality across sizes
• Assess limb/hoof alignment, straightness/symmetry, and forearm/chest muscle depth/length from the front
• A side view from the right further confirms balance, topline, and limb angles
• The evaluation from behind insights into back, croup, hips, buttocks, hindquarter, and hindlimb symmetry
• The perspective is used for assessing back muscling, vertebral column alignment, and left-to-right symmetry only if the horse is standing square.

Body

• Head size/shape are breed-specific and negligibly impact performance/lameness
• The neck acts as a lever and should be long, flexible, and convex
• Longer neck aids balance over jumping fences
• Distal forelimb bears more weight than distal hindlimb
• Forelimbs tend to "bounce", while hindlimbs "slide”.
• Well-muscled forelimbs support 60-65% of the horse's body weight
• Balance helps horses move, improve efficiency, and reduce musculoskeletal system stress

Proportions and Curvature of the Top Line

• Influenced by topline proportions/curvature, loin strength, wither sharpness, croup slope, underline length to back
• Neck is measure from teh poll to the withers
• Back is measure from teh withers to teh caudal end of the loin
• Hip is measure from the caudal loin to point of the buttock
• If shorter, neck limits flexibility/balance
• A too-long back results in a hollow (concave) back
• A short hip leads to reduced propulsion/downhill body configuration
• General guideline: neck length should be equal or greater thna teh back length; hip hould measure at least ⅔ the back length
• Shape depends on the S-curve of cervical vertebrae
• Ideally, the nec rises gracefully without dipping ventrally in front
• The thickest part should be at the ventral limits
• Ewe necks display a long, downward curve, with the neck appearing to attach low on chest
• Shoulder attachment is also important
• A steep one leads to less ideal dorsal to ventral neck ratio.
• Withers blend gently into the back, ending at the midpoint, and are suitable for saddle placement
• Neck/forearm muscles and ligamentum nuchae attach at the highest point of the withers without a dip
• Low withers hinder raising of the back when lowering/extending neck
• Well-sloped shoulders typically indicate properly positioned withers
• Longissimus muscles along the spine should be flat and strong and not sloped since the horse's help counteract gravity and support rider's weight
• Loin, from the last thoracic vertebra to teh lumbosacral junction, which should be mulcusled and short; "Long-backed" horses often have a long, weak loin, putting them at risk of chronic lumbar pain or vertebral damage
• Loin and coupling transfer motion from hindquarters trhough back to forehand
• Strong/well connected lions promote power, which can lack flexibility and may be short
• The Croup from th lumbrosacral to tail, should fairly long to ensure hip and articulation
• A topline that is shorter than the underline creates a balanced combination thta indicats good stride length.

Substance

• The thickness, depth and breadth of tissue
• Evaluating muscle substance considers its type, thickness, length + attachment position
• Important elements are weight, sizes, height and the rib (the degree of curvature; best observed from the rear), and the spring
• Well sprang ribs provide ample space for the heart, lungs, digestive
• Shalllow girth/slab sides = uncomfortable
• Size relates to weight
• Use cannon size, below, to gauge size; 4 cm *100 kg for riding horses -> 500 kg needs 20 cm
• Alignment is essential for movement; the shoulder, arm, forearm, should be proportional
• Straight bones -> Smooth movement, should align with the joints
• High-quality hooves with build

Forelimbs

• Equal length and size; when standing, even length should be seen by dropping a line between limb on the shouulder to ground in a straight line
• Toes and feet should point
• Humus slope - Optimal, humerus is optimal
• Muscle taper at elbow to provide flex
• carpals should be balances
• Devations -> strain -> hinge joints

Lateral View

• Moderate angles for Shock absorption
• Measuring shoulder (Scapular and withers) - angle becomes more upright as horse matures, the shorter angle causes increase of stride
• High performance wants horizontal
• Angle facilitates elbow to ground max extension
• Humerous Length
• Improvments to stirde / Quality
• elbow to fettloc -> straight; misalignment can result in force concentration (Carpus-function)
• Fetlocks
• Straighter hind
• The hoves should be well shaped
• Extreme can raise strain

Conformation Faults

• Can lead cause musculoskelatal injureise

Hindlimbs

• Engine
• .The horses and muscles determine preformacne

Lateral Vieww - hinds

• line from buttocks -> hocks ends behind heel -> standin hindlegs, and camper out
• gluteal msucles and connect back to limb
• hip and length, stride etc
• A foreleg is faster than the hind
• Gaskin to stilthe is the one that should be shorter

From the rear - Hinds - symmetrical/length and equality

Medial / lateral

• relationship in the hoof, with a band
• asymmetry + insight
• Level from front to back
• Straighter inside

Static examination

• Visual assessment of the horse’s back begins with
• observing the muscle contour from
• the side and checking the axial alignment from the rear. The dorsal spinous processes should be palpated
• to evaluate their alignment, as well as to detect any protrusion, depression, or abnormal interspinous distances.

_ Static/Hands on exam

• A systematic approach to avoid missing abnornmalilites
• A foor exam must be done after exam of the mussocletal
• The shape, and see if normal relative size - check for abnormalities - size, cracks, imbalance, etc
• Check after clean

Hands on exam

• Palpate for problems
• With the limb off the ground, pain may be elicited from the distal sesamoidean ligaments and phalanx if a fracture is present.
• Examine for problems/fractures

Carpus

Effective when carpus if flexed

Forelimbs

• check swelling

Tarsus

palpated -> synovitis

Dynamic examination

• is best carried out on a hard, level surface
• Surface (impact)
• A jogger is very important
• Head centered, a constant speed and line, head and neck can be an indicator of health issues
• handler should focus on forelimbs
• Gait changes indicate limb concerns

Character change

• important diagnosis consideration
• when to watch the stride
• head and pelvic

EQM400 2025 is finished