Section 6: Orthopaedics & Lameness General Lameness (General) Body conformation of Equine & Bovine Equine Lameness Stringhalt Upward fixation of patella (UFP) Curb Thorough pin Capped elbow Bursitis Hygroma Carpitis Sore shin Wind puff Tendonitis Capture myopathyem exam pov

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Section 6: Orthopaedics & Lameness - Complete Exam Notes

1. LAMENESS (GENERAL)

Definition: Any deviation from normal gait due to pain, mechanical restriction, or neuromuscular dysfunction.

Classification of Lameness

Type	Mechanism	Examples
Supporting limb	Pain on weight-bearing	Foot abscess, fracture
Swinging limb	Pain on protraction	Shoulder lameness
Mixed	Both phases	Upward fixation of patella
Mechanical	No pain - structural	Stringhalt, UFP, fibrotic myopathy
Neurological	CNS/PNS dysfunction	Wobbler syndrome, EPM

Grading of Lameness (AAEP Scale - Equine)

Grade	Description
0	No perceptible lameness
1	Difficult to observe, not consistent
2	Difficult to observe at walk/trot in straight line, consistent under certain conditions
3	Consistently observable at trot
4	Obvious at walk
5	Non-weight-bearing / complete

Examination of Lameness

History - onset, duration, work history, shoeing
Observation at rest - stance, posture, muscle atrophy
Palpation - heat, swelling, pain on pressure
Gait analysis - walk, trot, circle, hard/soft surfaces
Flexion tests - distal/proximal limb flexion
Hoof testers
Nerve blocks (perineural analgesia) - diagnostic
Imaging - radiography, ultrasonography, MRI, nuclear scintigraphy

Key Observation Points

Head nod in forelimb lameness: head goes DOWN when the SOUND limb contacts ground (rises when lame limb bears weight)
Hip hike in hindlimb lameness: hip of lame side rises higher during weight bearing
Toe dragging suggests neurological or mechanical hindlimb problem

2. BODY CONFORMATION - EQUINE & BOVINE

Equine Conformation

Forelimb - Ideal vs Faulty:

Region	Ideal	Fault	Predisposes to
Toes	Straight forward	Toe-in (pigeon-toed)	Interfering, brushing
		Toe-out (splay-footed)	Winging-in, forging
Pastern angle	45-50° (front), 50-55° (hind)	Broken forward (low)	Navicular, DDFT strain
		Broken backward (upright)	Ringbone, coffin joint trauma
Knees	Straight	Over at knee (buck-kneed)	Less serious
		Back at knee (calf-kneed)	Carpal chip fractures

Hindlimb Conformational Faults:

Sickle hock: Excessive hock angulation - predisposes to curb, bog spavin
Cow hocks (valgus): Hocks point inward - predisposes to bone spavin
Straight hock: Excessive straightness - predisposes to upward fixation of patella
Post-legged: Very straight limbs overall - UFP, osteochondrosis

Back Conformational Issues:

Sway-back (lordosis): Predisposes to back pain
Roach back (kyphosis): Predisposes to poor performance

Bovine Conformation

Limb Evaluation:

Viewed from front/behind and side
Claw shape: Key in cattle - wide base, correct angle (~50°)
Hock angle: ~150° ideal
Foot angle parallel - imbalance leads to white line disease, sole ulcers

Common Bovine Conformational Faults:

Fault	Description	Consequence
Sickle hock	Excess angulation	Corkscrew claw, curb
Cow hock	Medial deviation	White line disease lateral claw
Steep pastern	Upright foot	Sole bruising
Low/weak pasterns	Coon foot	Fetlock drop, flexor tendon issues

3. EQUINE LAMENESS (SPECIFIC CONDITIONS)

STRINGHALT

Definition: Involuntary, exaggerated hyperflexion of one or both hind limbs during movement.

Types:

Feature	Classic (Idiopathic)	Australian (Pasture)
Laterality	Usually unilateral	Bilateral
Cause	Unknown - possibly peroneal nerve	Toxic plants - Hypochoeris radicata (flatweed/dandelion)
Season	Year-round	Late summer/autumn (dry pasture)
Prognosis	Variable	Good if removed from pasture

Signs:

Hind limb snapped upward sharply toward abdomen on each step
Worse when backing, turning, or after rest
Gait looks like an exaggerated "goose-step"
Muscle wasting of lateral digital extensor / peroneus tertius (Australian type)

Pathology:

Axonopathy of the peroneal (fibular) nerve
Demyelination and axonal degeneration

Diagnosis: Clinical gait assessment; EMG; nerve biopsy

Treatment:

Australian type: Remove from pasture - most recover in 6-12 months
Classic type: Lateral digital extensor tenectomy (surgical resection of the tendon) - removes mechanical exaggeration
Phenytoin (100 mg/kg) has been used medically
Prognosis: Guarded for classic; good for Australian if caught early

UPWARD FIXATION OF THE PATELLA (UFP)

Definition: The medial patellar ligament becomes hooked over the medial trochlear ridge of the femur, locking the stifle in extension.

Mechanism:

In horses, the patella locks over the medial trochlear ridge to allow weight-bearing rest (normal "stay apparatus")
UFP = failure to unlock this mechanism
Predisposed by: straight/post-legged hindlimb, poor body condition, young horses, weakened quadriceps

Signs:

Severity	Clinical Presentation
Intermittent	Hind leg drags momentarily then jerks free; "catching"
Permanent	Limb locked in extension - cannot flex stifle or hock

Affected limb held in full extension
Limb dragged with toe on ground
Sudden release with "clunking" sound

Diagnosis: Clinical; palpate medial patellar ligament tightness; manually push patella medially to reproduce/release

Predisposing factors: Straight hindlimbs, poor BCS, rapid growth, young horses, draft breeds

Treatment:

Option	Indication
Exercise and hill work	Mild cases - builds quadriceps
Counter-irritant to medial patellar ligament	Mild-moderate
Medial patellar ligament desmotomy (cutting)	Definitive - most common surgical option
Medial patellar ligament splitting	Newer technique - avoids complications of desmotomy

Complications of desmotomy: Fragmentation of apex of patella (reported in some cases)

Exam Key Point: UFP = mechanical lameness, not pain-based.

CURB

Definition: Thickening/swelling at the plantar aspect of the hock, approximately 4 inches (10 cm) below the point of hock.

Anatomy: Involves the plantar tarsal ligament (also called the long plantar ligament)

Located at the level of the calcaneo-cuboid joint

Cause:

Trauma / strain of the plantar ligament
Predisposed by: sickle hocks, cow hocks

Signs:

Swelling visible on lateral view just below the point of hock
Acute: heat, pain, lameness
Chronic: firm, fibrous swelling; often without lameness

Diagnosis: Clinical inspection (view from the side); radiographs to rule out bone involvement

Differential: Thoroughpin (above hock), capped hock (on point)

Treatment:

Acute: rest, cold hosing, NSAIDs, support bandage
Chronic: usually just a blemish; corrective shoeing
Rarely: corticosteroid injection

THOROUGHPIN (TARSAL SHEATH TENOSYNOVITIS)

Definition: Distension of the tarsal (digital flexor) tendon sheath at the level of the hock.

Anatomy:

Sheath of the deep digital flexor tendon (DDFT) as it passes through the tarsal canal
Swelling appears above and to either side of the point of hock (between the Achilles tendon and the tibial bones)

Differentiating from Bog Spavin:

Feature	Thoroughpin	Bog Spavin
Location	Above point of hock; lateral/medial	Front of hock (tibiotarsal joint)
Structure	Tarsal tendon sheath	Tibiotarsal joint capsule
Can move fluid	Between both sides?	Yes (bog spavin)
Lameness	Rare	Usually minimal

Cause: Trauma, overwork, conformational predisposition (sickle hocks)

Signs:

Soft, fluctuant swelling on both sides of the Achilles tendon region
Usually not lame; cosmetic blemish

Treatment:

Rest, NSAIDs
Corticosteroid/hyaluronate injection
Drainage rarely needed

CAPPED ELBOW (OLECRANON BURSITIS)

Definition: Acquired bursa over the point of the elbow (olecranon), also called "shoe boil."

Cause:

Repeated trauma from the shoe or heel of the hoof striking the elbow when lying down
Common in horses that are stabled/tied

Signs:

Soft, fluctuant swelling at the point of the elbow
Usually non-painful, non-lame
May become firm/fibrous chronically

Treatment:

Remove the cause (shoe boil boot, pad)
Acute: drain and corticosteroid injection
Chronic/fibrous: surgical excision

BURSITIS (General)

Definition: Inflammation of a bursa (synovial sac designed to reduce friction over bony prominences).

Types in Horses:

Bursa	Common Name	Location
Olecranon	Capped elbow / shoe boil	Point of elbow
Calcaneal	Capped hock	Point of hock
Navicular bursa	Navicular bursitis	Deep to DDFT, behind navicular bone
Supraspinous	Fistulous withers	Over withers (often Brucella)
Bicipital	Bicipital bursitis	Shoulder region
Poll evil	Atlantal bursa	Poll region (often Brucella)

Septic Bursitis (Fistulous Withers / Poll Evil):

Cause: Brucella abortus (cattle-equine transmission), Actinomyces
Treatment: Long-term antibiotics, surgical debridement; zoonotic risk

General Treatment of Bursitis:

Rest
Cold/heat therapy
NSAIDs
Aspiration and corticosteroid injection
Surgery for chronic/septic cases

HYGROMA

Definition: Acquired bursa formed by repeated trauma over a bony prominence (not a pre-existing bursa).

Common Sites:

Knee (carpus) - "Carpal hygroma" - most common
Hock (calcaneal)

Cause: Repeated trauma from hard floors, falling (especially in cattle on concrete floors)

Bovine Hygroma:

Very common in dairy cattle on hard concrete
Carpal hygroma most frequent
Fluid-filled, soft, non-painful swelling at the front of the knee

Vs. Carpitis:

Feature	Hygroma	Carpitis
Location	Subcutaneous, over carpus	Within carpal joint/tendon sheaths
Lameness	Usually absent	Present
Fluid	Bursal fluid (subcutaneous)	Synovial fluid (intraarticular)

Treatment:

Remove cause (rubber mats, improved bedding)
Aspiration, corticosteroid injection
Chronic: surgical excision/curettage
Do not drain and bandage alone - high recurrence

CARPITIS

Definition: Inflammation of the carpus (knee joint complex in equids).

Also known as: "Popped knee"

Forms:

Type	Description
Acute	Synovitis/capsulitis from trauma or overwork
Chip fractures	Osteochondral fragments, usually dorsal
Chronic proliferative	New bone formation, periosteal reaction

Predisposing conformation: "Back at the knee" (calf-kneed) - excessive loading on dorsal surface

Signs:

Swelling at the front of the knee
Lameness (variable)
Pain on flexion
Crepitus in advanced cases

Diagnosis: Radiography (multiple views including flexed lateral, skyline); ultrasound

Treatment:

Acute: rest, cold therapy, NSAIDs, bandaging
Intra-articular corticosteroids/hyaluronate
Chip fractures: arthroscopic removal
Chronic: may require carpal arthrodesis

SORE SHIN (BUCKED SHINS / DORSAL METACARPAL DISEASE)

Definition: Periostitis of the dorsal cortex of the third metacarpal (cannon) bone. Also called "metacarpal periostitis."

Primarily affects: Young Thoroughbred racehorses (2-3 year olds) in early training

Pathophysiology:

High-intensity training causes microfractures in the dorsal cortex (stress remodeling)
Bone responds with periosteal new bone formation
Cycle: training stress → subperiosteal hemorrhage → periosteal proliferation → "bucked shins"
Can progress to: complete cortical fracture if training continues

Signs:

Pain on palpation of the dorsal cannon bone
Warm, firm swelling on the front of the cannon
Lameness (variable, can be subtle)
Worse after exercise

Diagnosis: Clinical; radiography shows periosteal reaction (may lag 2-3 weeks behind clinical signs); nuclear scintigraphy is most sensitive early

Treatment:

Rest is the cornerstone (4-8 weeks minimum)
NSAIDs
Controlled exercise program
Shock wave therapy
Pin firing / periosteal stripping (controversial, less used now)

Prevention: Gradual training progression; adequate rest between intense works

WIND PUFF (WIND GALL / FETLOCK SYNOVITIS)

Definition: Distension of the digital flexor tendon sheaths or fetlock joint capsule producing soft, fluctuant swellings around the fetlock.

Types:

Type	Location	Structure Involved
Articular wind puff	Palmar pouch of fetlock joint	Fetlock (metacarpophalangeal) joint capsule
Tendinous wind puff	On either side of flexor tendons	Digital flexor tendon sheath

Cause: Overwork, repetitive stress; very common in working horses

Signs:

Soft, fluctuant swellings in the palmar/plantar fetlock region
Usually bilateral and symmetric
Usually non-lame (cosmetic)
If unilateral + warm + lame = significant pathology

Exam Key Point: Wind puffs = usually bilateral, symmetrical, non-painful, no lameness. Unilateral + lame = concerning.

Treatment:

If non-lame: rest, support bandaging, cold therapy
Aspiration + corticosteroid if needed
Address underlying cause (shoeing, work surface, workload)

TENDONITIS (BOWED TENDON)

Definition: Inflammation/degeneration of the flexor tendons, most commonly the superficial digital flexor tendon (SDFT).

Also called: "Bowed tendon" (due to the characteristic bulge on the palmar cannon)

Most Common in: Thoroughbred/Standardbred racehorses, eventers

Anatomy - Sites:

Zone	Location
High bow	Upper third of cannon - most common
Middle bow	Mid-cannon
Low bow	Pastern region (pastern ligament involvement)

Pathophysiology:

Repetitive strain → micro-tears → fiber disruption
SDFT bears most load in high-speed work
Acute: hemorrhage and edema → chronic: fibrous (scar) tissue fills defect
Scar tissue is mechanically inferior → high re-injury rate

Signs:

Phase	Clinical Features
Acute	Hot, painful, swollen "bow" on palmar cannon; acute lameness
Chronic	Firm, fibrous enlargement; little lameness; "old bow"

Diagnosis:

Clinical palpation
Ultrasound (gold standard): shows fiber disruption, core lesion, % cross-sectional area affected

Treatment:

Phase	Treatment
Acute	Box rest, cold therapy (ice 20 min q.i.d.), NSAIDs, support bandage
Subacute/chronic	Controlled exercise; tendon splitting (decompression); intralesional treatment
Biological	PRP (platelet-rich plasma), stem cells, IRAP
Surgical	Superior check ligament desmotomy (reduces load on SDFT)

Prognosis:

Return to full athletic use: ~50-60% in racehorses
Re-injury rate is HIGH (up to 80% in racehorses)

4. CAPTURE MYOPATHY

Definition: A stress/exertion-induced myopathy (muscle degeneration) occurring in wild or recently captured animals due to extreme physiological stress and physical exertion.

Also known as:

Exertional myopathy
Transport myopathy
Stress myopathy
Overstraining disease
White muscle disease (when nutritional Se/Vit E component involved)

Species affected: Most commonly wild ungulates (deer, antelope, zebra, gazelle), but also: wild birds, reptiles, some domestic animals under extreme stress

Pathophysiology:

Extreme physical exertion + psychological stress → massive sympathoadrenal activation
Lactic acidosis + ATP depletion → muscle cell membrane failure
Ca²+ influx into muscle cells → mitochondrial damage → rhabdomyolysis
Myoglobinuria → renal failure
Hyperthermia, DIC can follow

Key Biochemical Cascade:

Stress + Exertion
      ↓
Catecholamine surge + anaerobic metabolism
      ↓
Lactic acidosis + hyperthermia
      ↓
Muscle membrane damage → rhabdomyolysis
      ↓
Myoglobinuria → renal tubular necrosis
      ↓
Death (often hours to days later)

Forms:

Form	Onset	Features
Peracute	During capture	Collapse, hyperthermia, death within hours
Acute	Hours after	Stiff, unable to rise, myoglobinuria
Subacute	24-72 hrs	Found dead/moribund in holding
Chronic	Days-weeks	Muscle wasting, fibrosis

Clinical Signs:

Muscle stiffness, reluctance to move
Recumbency
Trembling, hyperthermia
Dark (port-wine) urine = myoglobinuria
Tachycardia, tachypnoea
Death in severe cases

Gross Pathology:

Pale, white/grey streaked muscles (especially large muscle groups: epaxial, hindquarters)
"White stripes" in myocardium
Kidneys: dark-brown discoloration, tubular necrosis

Histopathology:

Zenker's hyaline degeneration of muscle fibers
Coagulative necrosis
Mineralization of necrotic fibers

Diagnosis:

CK (creatine kinase) - markedly elevated (may be 10,000-100,000+ IU/L)
AST elevated
Myoglobinuria (positive urine dipstick for blood without RBCs)
Metabolic acidosis (lactic acid)
BUN/creatinine elevated (renal failure)
Hypocalcemia, hyperkalemia

Treatment:

Prevention is better than treatment
Minimize stress, rapid processing
Sedation/chemical restraint BEFORE capture stress escalates
Supportive care: IV fluids (saline/Ringer's), bicarbonate (correct acidosis)
Vitamin E + Selenium (if deficiency suspected)
NSAIDs (meloxicam, flunixin)
Corticosteroids (controversial)
Cooling measures
Supportive dark, quiet environment

Prevention (key exam points):

Minimize chase distance and time
Adequate chemical immobilization
Cover eyes (blindfold) after capture - reduces visual stress
Minimize handling time
Keep cool
Avoid capture in hot/humid conditions
Do not capture animals that are already in poor condition

Exam-focused distinction from other myopathies:

Condition	Key Difference
Capture myopathy	Wild/recently captured animals; stress + exertion; rhabdomyolysis
Azoturia (Monday morning disease)	Horses; dietary; glycogen storage; after rest on high grain diet
White muscle disease	Nutritional deficiency (Se/Vit E); young animals; no stress trigger
Malignant hyperthermia	Halothane trigger; genetic; pigs most common

QUICK REVISION TABLE - ALL CONDITIONS

Condition	Key Anatomical Structure	Key Feature	Treatment
Stringhalt	Peroneal nerve/lateral digital extensor	Exaggerated hind limb hyperflexion	Tenectomy / remove from pasture
UFP	Medial patellar ligament	Locked stifle in extension	Medial patellar ligament desmotomy
Curb	Plantar tarsal ligament	Swelling below point of hock	Rest, NSAIDs
Thoroughpin	Tarsal tendon sheath (DDFT)	Swelling above/beside point of hock	Corticosteroid injection
Capped elbow	Olecranon bursa	Swelling at point of elbow	Shoe boil boot, drain/inject
Hygroma	Acquired subcutaneous bursa	Over carpus in cattle; no lameness	Remove cause, mat flooring
Carpitis	Carpal joints	Swelling at front of knee; lameness	Rest, arthroscopy for chips
Sore shin	Dorsal MC3 periosteum	Young racehorses; front cannon pain	Rest 4-8 weeks
Wind puff	Fetlock synovial structures	Bilateral symmetrical; non-lame	Bandage, address workload
Tendonitis	SDFT (palmar cannon)	"Bow"; ultrasound diagnosis	Rest, PRP, check desmotomy
Capture myopathy	Large muscle groups	CK ↑↑↑; myoglobinuria; wild animals	Prevention; fluids; Vit E/Se

HIGH-YIELD EXAM MNEMONICS

"Lameness Head & Hip Rule":

Forelimb lame: Head NODS DOWN on SOUND limb
Hindlimb lame: HIP HIKES UP on LAME side

"CATS get Capture myopathy" (C=CK elevated, A=Acidosis lactic, T=Temperature up, S=Stress trigger)

Swellings around the hock (top to bottom):

Above point = Thoroughpin (tarsal sheath)
ON the point = Capped hock (calcaneal bursa)
Below the point = Curb (plantar ligament)

Wind puff vs pathological effusion:

Bilateral + symmetrical + no heat + no lameness = Wind puff (benign)
Unilateral + warm + lame = Investigate (septic/traumatic synovitis)

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