Flexural Deformities, Osteochondrosis, and Physitis in Horses

Flexural Deformities (Contracted Tendons, Club Foot, Knuckling)

Core Definition: The inability to fully extend a limb (contracture) or excessive tendon relaxation (laxity).

- Types and Etiology:
  - Congenital: Result of uterine malposition, genetics, or disparity in length between bone and the musculotendinous unit.
  - Acquired: Typically caused by chronic pain (from physitis, OCD, or injury) inducing a reflex muscle contraction that shortens the flexor unit.
- Anatomical Targets & Key Ages:
  - DIP Joint (Club Foot): Most common; acquired form usually appears at 3–6 months of age.
  - Carpal Joint: Congenital or acquired at 1–6 months.
  - Fetlock Joint (Knuckling): Acquired form usually appears at 9–18 months.

Clinical Findings:

- - Walking on the toe, upright hoof with elongated heel (club foot), or knuckling over at the carpus/fetlock.
  - Progressive worsening, even in foals seemingly healthy at birth.

Treatment Protocols:

- - Medical (Congenital): IV Oxytetracycline (for tendon relaxation), NSAIDs, splints/casts, and stall rest.
  - Conservative (Acquired): Nutritional correction (slowing growth), corrective farriery (toe extensions), and analgesia.
  - Surgical: Inferior check ligament desmotomy (most successful for DIP joint); superior check ligament desmotomy for fetlocks; tenotomy as a salvage procedure.

Osteochondrosis (Osteochondritis Dissecans, OCD)

Core Definition: A failure of endochondral ossification resulting in lesions of articular cartilage or subchondral bone in young horses.

Multifactorial Etiology: Rapid growth, high-carbohydrate diets, mineral imbalances, genetics, and biomechanical trauma.
Clinical Manifestations:
- Nonpainful joint effusion (distention) is the most common sign, particularly in the tarsocrural (hock) and femoropatellar (stifle) joints.
- Lameness may be absent or mild, except in cases involving the shoulder (severe lameness/muscle atrophy) or loose fragments in training yearlings.

Diagnostic Methods:

- Radiography: Primary tool for identifying intra-articular osteochondral fragments.
- Arthroscopy: Required to identify lesions restricted solely to the cartilage that are not visible on radiographs.

Management & Treatment:

- Conservative: Restricting exercise and decreasing feed intake to slow growth; ensuring proper copper/mineral supplementation.
- Surgical (Treatment of Choice): Arthroscopic removal of fragments, debridement of damaged cartilage, and joint lavage.

Physitis (Epiphysitis, Physeal Dysplasia)

Core Definition: Inflammation of the growth plate (physis) in young horses.

Primary Causes: Malnutrition, obesity, excessive exercise, hard/dry ground, and conformational defects.
Anatomical Locations: Most commonly affects the distal extremities of the radius, tibia, and metacarpal/metatarsal bones.

Clinical Indicators:

- Heat, pain, and swelling around growth plates.
- "Boxy" appearance of affected joints due to visible flaring at the growth plate.
- Often associated with mild lameness and contracted tendons.

Treatment and Prevention:

- Nutritional Management: Decrease food intake to slow growth rate; limit protein to <10% of dry matter.
- Mineral Balance: Specifically adjust the Calcium:Phosphorus ratio to 1.6:1.0.
- Environmental Management: Restrict exercise to soft surfaces (sand, deep straw) and ensure frequent, careful hoof trimming.

Flexural Deformities, Osteochondrosis, and Physitis in Horses

Flexural Deformities (Contracted Tendons, Club Foot, Knuckling)

Core Definition: The inability to fully extend a limb (contracture) or excessive tendon relaxation (laxity).

Types and Etiology:

Congenital: Result of uterine malposition, genetics, or disparity in length between bone and the musculotendinous unit.

Acquired: Typically caused by chronic pain (from physitis, OCD, or injury) inducing a reflex muscle contraction that shortens the flexor unit.

Anatomical Targets & Key Ages:

DIP Joint (Club Foot): Most common; acquired form usually appears at 3–6 months of age.

Carpal Joint: Congenital or acquired at 1–6 months.

Fetlock Joint (Knuckling): Acquired form usually appears at 9–18 months.

Clinical Findings:

Walking on the toe, upright hoof with elongated heel (club foot), or knuckling over at the carpus/fetlock.

Progressive worsening, even in foals seemingly healthy at birth.

Treatment Protocols:

Medical (Congenital): IV Oxytetracycline (for tendon relaxation), NSAIDs, splints/casts, and stall rest.

Conservative (Acquired): Nutritional correction (slowing growth), corrective farriery (toe extensions), and analgesia.

Surgical: Inferior check ligament desmotomy (most successful for DIP joint); superior check ligament desmotomy for fetlocks; tenotomy as a salvage procedure.

Osteochondrosis (Osteochondritis Dissecans, OCD)

Core Definition: A failure of endochondral ossification resulting in lesions of articular cartilage or subchondral bone in young horses.

Multifactorial Etiology: Rapid growth, high-carbohydrate diets, mineral imbalances, genetics, and biomechanical trauma.

Clinical Manifestations:

Nonpainful joint effusion (distention) is the most common sign, particularly in the tarsocrural (hock) and femoropatellar (stifle) joints.

Lameness may be absent or mild, except in cases involving the shoulder (severe lameness/muscle atrophy) or loose fragments in training yearlings.

Diagnostic Methods:

Radiography: Primary tool for identifying intra-articular osteochondral fragments.

Arthroscopy: Required to identify lesions restricted solely to the cartilage that are not visible on radiographs.

Management & Treatment:

Conservative: Restricting exercise and decreasing feed intake to slow growth; ensuring proper copper/mineral supplementation.

Surgical (Treatment of Choice): Arthroscopic removal of fragments, debridement of damaged cartilage, and joint lavage.

Physitis (Epiphysitis, Physeal Dysplasia)

Core Definition: Inflammation of the growth plate (physis) in young horses.

Primary Causes: Malnutrition, obesity, excessive exercise, hard/dry ground, and conformational defects.

Anatomical Locations: Most commonly affects the distal extremities of the radius, tibia, and metacarpal/metatarsal bones.

Clinical Indicators:

Heat, pain, and swelling around growth plates.

"Boxy" appearance of affected joints due to visible flaring at the growth plate.

Often associated with mild lameness and contracted tendons.

Treatment and Prevention:

Nutritional Management: Decrease food intake to slow growth rate; limit protein to <10% of dry matter.

Mineral Balance: Specifically adjust the Calcium:Phosphorus ratio to 1.6:1.0.

Environmental Management: Restrict exercise to soft surfaces (sand, deep straw) and ensure frequent, careful hoof trimming.