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

2. 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

3. 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

4. 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

5. 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.

6. Sweeny

7. 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

8. 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

9. 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!

10. The Knee Joint

11. 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

12. 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.

13. 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

14. 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

15. 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”

16. 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

17. Ringbone

18. Front Limb – Navicular Bone
“Navicular Syndrome” aka Podotrochleosis
Most common cause of intermittent, shifting forelimb lameness
Most common in horses 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

19. 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

20. 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)

21. 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

22. 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

23. Locked Stifles
NORMAL
LOCKED

24. 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

25. 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!

26. 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!

27. 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

28. 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!

29. 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

30. 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

31. 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

32. 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).

33. 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

34. 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

35. 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

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