Lameness – Part 2: Specific Diseases INAG 120 – Equine Health Management November 2, 2011

Common Lameness Disorders FRONT LIMB Shoulder Knee Fetlock Pastern Navicular HIND LIMB Stifle Hock Fetlock Pastern Joints are used to absorb shock, permit frictionless movement, and effectively bear the weight of the horse’s body. Made up of the two bones on either end covered by articular cartilage. Synovial fluid helps to keep the joint properly lubricated

Front Limb - Shoulder Signs of shoulder lameness: Head lifts when limb moves forward Little flexion of limb (low foot arc) Swinging out of limb to avoid flexion Failure to reach out (shortened cranial phase) Fixation of shoulder joint  inability to move Hard or soft ground often has same effect if level (may be slightly worse on soft ground) Stumbling

Lameness in the Shoulder Arthritis – Usually caused by trauma Persistent lameness In foals, other joints also involved Tx: injections with steroid (usually cortisone) followed by hyaluronic acid

Lameness in the Shoulder Sweeny – Atrophy of muscles around shoulder Paralysis of suprascapular nerve “Popping” of the shoulder when horse walked toward examiner Trauma to the shoulder  damage to the suprascapular nerve that traverses over the top of the neck of the scapula. This nerve innervates the two large muscles of the shoulder blade, the supraspinatus and infraspinatus. If damaged severely enough, nerve quits functioning  loss of function and atrophy of the 2 scapular muscles. Clinical Signs: Pain and inflammation muscular weakness Denervation atrophy (Within two weeks the shoulder muscles become noticeably shrunken and the central ridge of the shoulder blade bone becomes prominent. Muscular denervation atrophy happens much quicker and more pronounced than with atrophy from disuse which may take weeks or months to develop ) Treatment: Wound treatment and reducing inflammation right away (ice packs, DMSO, NSAIDs) absolute stall rest for 14 days Treatment after the first two weeks should be stall rest with hand walking for 10 minutes twice daily for five weeks. Sweeny with no improvement in five weeks may indicate the need for surgery, where a pressure relieving technique involving creating a notch in the neck of the scapula, underneath the nerve, In cases where surgery is not done the horse should be stall rested for up to 18 months with the daily hand walking. This is done until evidence that the muscles of the shoulder are returning at which time turn out is begun slowly. Prognosis: Prognosis = good but may require prolonged rest. Loss of motor function, evidenced by an outward deviation of the shoulder on weight bearing, for longer than two weeks indicates there is probably complete disruption of the nerve and regrowth will be necessary. This generally occurs at the rate of a millimeter a day (1 inch a month). For severe injury this may be as long as 12 to 18 months.

Sweeny

Front Limb - Knee Site of many developmental orthopedic diseases Signs: Stand with knee flexed Failure to reach out in stride Lower foot arc Stiff-legged paddling gait Carpal flexion test, joint blocks good tools for diagnosis

Front Limb - Knee Fractures Common in race horses, jumpers, hunters Factors = speed, immaturity, long limb length, position of rider, distances run, firm surface Most common is chip fracture (also slab or fragmented fractures – less common) Involves only one joint surface Fracture of the 3rd carpal bone (slab) © Clark Equine Clinic

Lameness in the Knee Anatomy of the knee: Two stacked rows of cuboidal bones (6) Three joint spaces All held together by intercarpal ligaments Radius above, cannon below  compressive force! Faulty conformation (back at the knee)  predisposed Decreased incidence in European racehorses as opposed to American  why? European racehorses: Often over at the knee Begin racing as 3-year olds rather than 2-year olds? Race on Turf as opposed to dirt? Run both clockwise and counter-clockwise? Turns are more subtle than American race courses!

The Knee Joint

Front Limb - Fetlock Bones of the Fetlock Joint: Cannon, Proximal Sesamoid Bones (2), Long Pastern Bone Fractures Fairly common! Usually on the medial side of the long pastern bone, less often on end of cannon Former seen in race horses on hard surfaces, latter when training begins Lameness most obvious at trot Gets worse with work Usually can’t produce pain with palpation, but can feel heat Use opposite limb as comparison

Lameness – Fetlock Fracture of sesamoid bones: Common in racing Thoroughbreds, Standardbreds and Quarter Horses Forelimbs most commonly affected in TB and QH, hindlimbs in STB Lameness is very pronounced – often non-weightbearing Swelling, heat, pain Fetlock held rigid during movement This is the most common type of sesamoid bone fracture. These are typically the result of strain placed on the suspensory apparatus at the level of attachment of the suspensory ligament branch. Injury to the suspensory ligament branch may occur concurrently with the fracture. If significant injury to the suspensory branch is present the prognosis will be poorer. Surgical removal of the apical fragment is the treatment of choice for these fractures. Small fracture fragments may be removed with little damage to the attachment of the suspensory branch. The larger the fracture fragment that is removed, the more disruption of the suspensory branch attachment that occurs and the poorer the prognosis.

Front Limb – Pastern Joints TWO joints (Long pastern-short pastern and short pastern-coffin bone) Ringbone New bone growth on bones of pastern joint(s) leading to arthritis and fusion of joints High = top joint Low = bottom joint Commonly caused by trauma  strain on collateral ligaments, joint capsule attachments to bone, wire cuts; or direct trauma  leads to trauma to periosteum and bone formation Base-wide conformation  strain on medial surfaces and base-narrow lateral surfaces toe-in or out increases forces

Pastern Joint - Ringbone Articular vs. Non-articular Non-articular due to inflammation of the periosteum Most common in non-speed horses with coarse boxy pasterns Horses with high heels and short toes with trappy gaits Peri-articular  often doesn’t cause lameness; after rest, may also lack heat, pain or swelling; Articular  chronic lameness with variable degrees of swelling heat and pain; lateral movements such as longeing = intensified pain; lack of flexion with high ringbone Nonarticular ringbone doesn’t involve joint surface, most common as high ringbone

Pastern Joint – Ringbone Articular High ringbone Horse used for high speed that make quick stops, short turns or rapid twisting movements Overly upright pasterns  increased concussion on joint Signs of lameness are not specific Fusion of pastern joint common If high articular ringbone – lameness present until fusion takes place. Surgical fusion may be performed (screws + cast from knee to cover foot for 6-7 weeks; then bandage support when fusion is complete, stall confinement for 8 weeks  hand-walking) no free exercise until after 16 weeks (may need up to 1 year, though!) If coffin bone involved  BAD NEWS! Probably never get a sound riding horse Low ringbone may lead to “buttress foot”

Diagnosis: early using thermal imaging (will show increased heat in the pastern); radiology is definitive diagnostic tool. Treatment: guarded prognosis for return to athletic endeavors – pt and modified training (non-articular is obviousy better) Early prior to bone growth – robert jones bandage or light cast; warm moist heat/cold therapy to decrease inflammation; light therapy to increase circulation; proper shoeing and modification of training technique. Chronic cases: pain releiving drugs, stall rest, nerving High articular ringbone: systemic/intra-articular therapies; surgical invovlvement possible (fusing) Chronic articular: surgical fusing and post-surgical casting Rockered toed shoes

Ringbone

Front Limb – Navicular Bone “Navicular Syndrome” aka Podotrochleosis Most common cause of intermittent, shifting forelimb lameness Most common in horses 4-15 years old Most common lameness of horses between 4 and 9 yo Hereditary (small feet, faulty conformation) Highest incidences in Quarter Horses and Standardbreds Geldings > Stallions > Mares Lameness exhibits as heel pain Broad spectrum of conditions which affect the navicular bone

Navicular Syndrome Predisposing factors: @ walk and trot Poor conformation Upright pasterns Inappropriate exercise Resilient surfaces Improper/irregular trimming Long toe-low heel (broken-back axis) @ walk and trot Lands toe first  excessive wear of the toe, bruising Lower limb flexion test  aggravates 80% of horses Stiff shuffling gait with high head and rigid neck When circled, limb on inside will be worse, head held to outside of circle Was originally thought to be an arthiritic condition of the bone itself and it’s consequential effects on the bursa and flexor tendons Horse with laminitis is similar except that it lands heel first! Distinguish from bruising, SSD (sheared heels, etc.) If chronic and long-present -> foot will change shape (heels contract and rise to keep pressure off frog), sole becomes more concave and a narrowing in the quarters; if only one foot affected – it will be smaller Treatment: Corrective trimming and shoeing; drugs that may affect vascularization of foot (isoxuprine and dicumorol); pain alleviation

Hind Limb – Stifle Bones involved: femur, tibia, patella (knee cap) Most commonly mis-diagnosed lameness area (overdiagnosed) Hard to discern differences due to stifle vs. hock Common Problems: DOD … Upward Fixation of the Patella Arthritis and inflammation (gonitis)

Upward Fixation of the Patella Locked Stifles Middle and medial patellar ligaments get “caught” on the femur Patella should be able to slide during movement, if ligaments stuck, patella can’t move May be intermittent or complete Acute = hindlimb locked in extension Stifle and hock can’t flex (but fetlock can) Catching (not complete locking) also possible

Upward Fixation of the Patella Diagnosis: Catching most noticeable when horse is turned in a tight circle towards affected limb Walk up and down slope – crouched position going up, jerky gait down Toe drag if limb locked Palpation – patella locked in extension Treatment: Training to improve muscle tone Avoid exercise in soft areas Surgery as last resort

Locked Stifles NORMAL LOCKED

Stifle – Arthritis and Gonitis Gonitis = inflammation Many causes Distension of the stifle joint Gluteal muscles may be atrophied Wearing of toes in the hind end (toe drag) More lame when ligaments or cartilage involved Shortened stride (failure to reach forward) Hip hike Arthritis = bony changes

When the stifle flexes the hock also flexes and vice versa! Hind Limb – Hock Bone spavin Bog spavin Fractures Curb Stringhalt Shivers Capped Hock Soft Tissue DOD (Nutrition Course) When the stifle flexes the hock also flexes and vice versa!

The Hock Joint 6 cuboidal bones, tibia, cannon, 4 joints Hock works as a hinge Most movement occurs between the tibia and the tibial tarsal bone Hock is the pivotal hind limb joint – all equine exercise disciplines rely on it for performance The hock absorbs most concussive forces Most common site of stress related injuries!

Hock Lameness First noticeable sign is stiffness/soreness in lumbar region of back Poorly trained chiropractors may “adjust” a horse that really has a primary hock problem! Pain around inside splint bone Swelling and pain in the joint itself

Specific Conditions Bone Spavin: General term for degenerative joint disease or osteoarthritis in the hock joint Often in both hocks History = back stiffness/soreness with lameness that may go away with exercise Excessive wear on the outside of the shoe/hoof Bony enlargement just below and behind the chestnut Flexion test!

Specific Conditions Bog Spavin: Curbed Hock General term for distension of joint capsule Present on inside front of the hock! Usually representative of an underlying hock problem! Curbed Hock Sprain of the ligament that runs down the back of the hock Common in horses with sickle-hocked conformation

Specific Conditions Capped Hock Stringhalt Hematoma at the point of the hock Often due to trauma (kicking walls, etc.) Avoid drainage due to potential for infection Stringhalt Excessive involuntary flexion of the hock joint Usually isolated Causes unknown

Specific Conditions Stringhalt Study in Australia: Appears in Late Summer  peaking in February Associated with droughty summers All breeds affected but TBs more, ponies less Recover when removed from paddocks containing catsear or dandelion Cases appear from late summer with a peak in February and are often associated with drier than normal summers. All breeds may be affected by Australian Stringhalt, although thoroughbreds seem to be more susceptible and ponies less susceptible. Horses will usually recover if moved to a paddock where they are not grazing Catsear or Dandelion. Recovery can take a few days or up to 18 months. The average recovery period is 6-12 months. The anticonvulsant drug Dilantin® does ease the signs of the disease and can help to hasten recovery. Some severe cases that have not responded to being removed from pasture can have a surgical treatment. The surgery involves removing the lateral digital extensor tendon in the hind leg. This treatment has variable results but in some cases has proven to be very worthwhile

Specific Conditions Shivers Involuntary muscle movements of limbs and tail May be caused by EPSM – most other causes unknown Usually most visible when trying to back a horse Jerks foot and holds it above the ground in flexed position EPMS – Equine Polysaccharide Storage Myophathy Usually affects heavy breed horses. EPSM is a genetic predisposition to fail to digest grains properly in the horse. The result leads to damage to muscle tissue during exertion. The Quarter Horse community calls the condition PSSM (Polysaccharide Storage Myopathy).

Treatment Terminology Rest with Controlled Exercise: Out of work (time off!); moderate controlled exercise such as daily hand-walking Physiotherapy: Hydrotherapy COLD – up to 48 hours post-injury to reduce inflammation HOT – 48 hours after injury to reduce tension, relieve pain

Treatment Terminology Joint Lavage: Washing dead tissue out of joint with large amounts of sterile fluid DMSO (dimethyl sulfoxide): Topical application can reduce joint inflammation Wear gloves! Corticosteroids: Anti-inflammatory – helps reduce harmful enzymes in synovial fluid Usually directly injected into joint

Treatment Terminology NSAIDs: Non-steroidal anti-inflammatory  pain relief for soft tissue injuries (Bute, Banamine, Aspirin) Hyaluronic Acid (HA): Natural part of synovial fluid used to treat synovitis injected directly into joint (after steroids) Horses often show immediate, long-lasting relief Joint Fusion: Surgical repair of arthritis

Treatment Terminology Counterirritation: Blistering, firing, ultrasound to speed healing