Developmental orthopedic diseases (DODs) refer to a range of non-infectious conditions that affect the musculoskeletal system of growing horses.
These conditions arise from an interruption in the normal development of cartilage, bone, or soft tissue (joint capsule, tendon, or ligament).
While some developmental issues are apparent at birth, others occur later as the horse grows. Conditions such as osteochondrosis and physitis can affect any breed of horses and are a common cause of pain and lameness. 
Some developmental orthopedic diseases influence future performance, depending on what part of the horse’s joint is affected. 
Developmental Orthopedic Diseases
The exact percentage of horses affected by DODs is unknown, however, prevalence is known to be high in certain breeds.
In a study of 392 Warmbloods, Standardbreds, and Thoroughbreds, 66.3% of foals were affected by developmental orthopedic diseases. 
Key factors in the development of equine orthopedic disorders likely involve a combination of the following causes: 
- Genetics: Some breeds may be genetically predisposed to DODs
- Nutrition: Lack of complete or imbalanced nutrients provided in the diet of pregnant or lactating mares and foals
- Rapid growth rate in foals and obesity due to excess dietary energy provided in their feeding program
- Trauma or stress exerted on developing cartilage and bones
- Excessive exercise at a young age or a lack of activity
A thorough physical evaluation by a veterinarian is necessary to identify abnormalities of the developing skeletal system in young horses. 
If your veterinarian suspects your horse has a developmental orthopedic disease, diagnostic radiographic or nuclear imaging and blood tests may be required to make an accurate diagnosis.
6 Common Developmental Orthopedic Diseases in Horses
1) Equine Osteochondrosis
Osteochondrosis describes abnormalities in the differentiation and maturation of cartilage. The condition impairs the normal bone formation process in which cartilage is gradually replaced by bone (endochondral ossification). 
Physical signs of osteochondrosis vary according to the joint(s) affected. Common signs include non-painful joint swelling and stiffness and an upright limb conformation.
Foals under six months of age with osteochondrosis may spend more time lying down and have difficulty moving normally. Increased joint stiffness and lameness may become apparent with the start of training.
Physical examination, x-rays, ultrasonography, arthroscopy, scintigraphy, or magnetic resonance imaging (MRI) are often used to diagnose osteochondrosis.
Diagnostic imaging often indicates abnormal cartilage growth and the presence of bone fragments in the joints when osteochondrosis is present.
Treatment of osteochondrosis depends on the severity of the condition and the specific joints affected. Horses with mild cases of osteochondrosis may recover without intervention.
If rapid growth is occurring in horses with osteochondrosis, restricted exercise and dietary modifications that reduce energy intake can help address the condition. Appropriate mineral supplementation is also required to address deficiencies in the diet. 
In some cases, surgery may be necessary to restore joint health. Surgical intervention may be necessary to remove damaged cartilage, osteochondral fragments, and compromised bone present beneath the affected cartilage. 
2) Equine Physitis (Physeal Dysplasia)
Previously referred to as epiphysitis, physitis is a DOD that describes swelling around the cartilaginous growth plates (areas within the bones from which growth or lengthening occurs) of specific long bones. One or multiple growth plates may be affected. 
Physitis is most prevalent in young horses that are growing rapidly and carrying excess weight. If a foal grows faster than its growth plates can develop bone (ossify), the bones can sustain structural damage. 
Potential causes of physitis include poor or imbalanced nutrition, such as imbalanced calcium to phosphorus ratio or mineral deficiencies in the diet.
Overfeeding and rapid growth are not believed to be the only factors that contribute to physitis. Instead, several factors are likely involved in the development of the condition.
Affected joints typically feel warm and firm when touched and have a boxed-shaped appearance.
Radiographs, ultrasound, and MRI help confirm a diagnosis of physitis. The most common sign of the condition is irregular and widened growth plate. To diagnose infection as a cause of physitis, synovial fluid is extracted from the affected joint and assessed. 
In some cases of physitis, the condition resolves on its own as the skeleton matures and growth plates close. However, some horses require treatment to address the condition.
Potential interventions may include feeding grass hay rather than alfalfa hay, avoiding feeding high-energy concentrates, ensuring the diet is balanced in vitamins and minerals, and weaning foals if they are old enough.
Horses with physitis may require restricted exercise to avoid inflicting further trauma on the affected growth plates.
Physitis caused by infection requires treatment with antibiotics and anti-inflammatory medications.
In rare cases, physitis can result in premature closing of affected growth plates, thus causing angular limb deformities.
3) Equine Angular Limb Deformities (ALDs)
Angular limb deformities (ALDs) are a type of DOD found in young, growing horses. This condition results in the development of crooked legs in young horses causing either a knock-kneed or bowlegged appearance. 
- Swelling in affected joints
- Warmth/heat in affected joints
- Inflammation of a growth plate (physitis)
- Ligament laxity
- Excessive wearing of the inside or outside of the hoof wall
- Incomplete bone formation of the knee (carpus) or hock (tarsus)
- Bone collapse within the joints (on radiographs)
ALDs can typically be diagnosed from a physical examination that includes observing the limbs from the front, rear, or side of the horse.
Radiographs are useful for determining the location of the ALD, the degree of deformity, and the condition of the bones and growth plates in an affected joint.
Treatment of an ALD depends on the joints affected and the severity of the condition. Your veterinarian may recommend the following treatments:
Non-surgical: Foals with a mild ALD may require stall rest to reduce stress on the affected joint. Corrective trimming, the use of glue on shoes, and the application of a splint or cast on the affected leg may be necessary to encourage an ALD to correct on its own. 
Surgical treatments aim to either slow or increase the growth rate of one side of the affected bone.
Surgery may also be necessary to correct deformities after affected bones have completed their rapid growth phase and if growth plates have closed. A corrective osteotomy involves removing a wedge of bone and restabilizing the bone with plates and screws. 
4) Equine Flexural Limb Deformities (FLDs)
A DOD that affects foals, flexural limb deformities most commonly occurs in newborns and those up to 14 months of age. 
The condition describes a state in which the tendons are excessively contracted or relaxed.  As a result of these tendon abnormalities, the condition can result in a range of conformation problems.
FLDs may be present at birth (congenital) due to incorrect position of the foal in the uterus, abnormal fetal development, genetic defects, diet (excess energy provided and/or mineral imbalances), and disease or malnutrition in the mare or foal. 
Clinical signs of FLDs in foals can include: 
- Trembling in the joints
- Knuckling (a condition where the fetlock joint is excessively straight)
- Walking on the toes and not bearing weight on the heels
- Clubfoot hooves with concave toes (hooves are excessively upright)
- Inability to stand (occurs with tendon laxity)
- Back-at-the-knee conformation (occurs with tendon laxity)
- Dropped fetlocks (occurs with tendon laxity)
- Walking on the heels (occurs with tendon laxity)
Diagnosis of FLDs is based on a physical examination. Radiographs (x-rays) and other diagnostic imaging strategies may assist in making an accurate diagnosis.
Early recognition and accurate diagnosis are essential for improving treatment outcomes. Treatments for an FLD involving contracted tendons may include: 
Adjunct Therapies: Bandaging, splinting, and physical therapy to aid in promoting/supporting normal conformation.
Regulated exercise: Reduced exercise or stall rest may be necessary to encourage tendon laxity if they are overly contracted.
Foals with overly relaxed tendons may require controlled exercise that is gradually increased as the laxity improves. Shoes (typically a glue-on type) with heel extensions are commonly used.
Therapeutic farriery: Shoeing and trimming may be used to promote proper conformation.
Medication: Intravenous oxytetracycline may be used to promote relaxation in affected tendons. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be administered to reduce inflammation and pain.
Surgery: In severe cases, surgical intervention involving transecting the inferior check ligament (desmotomy) to alleviate tension on the deep digital flexor tendon may be necessary. 
5) Cervical Vertebral Malformation (CVM)
This developmental orthopedic disease affects the nerves and muscles of foals. CVM can also occur in older horses but is only considered a DOD in growing horses.
Cervical vertebral instability: This condition occurs when the neck is flexed due to dynamic spinal cord compression between the third and fifth vertebrae. Horses between four and 18 months of age are most commonly affected.
Cervical static stenosis: This condition occurs in any neck position and is caused by a narrowing of the cervical canal between the fifth and seventh cervical vertebrae. Horses between one and four years of age are most affected.
CMV has been reported in Thoroughbreds, Quarter Horses, and Warmbloods. This condition has not been reported in miniature horses. 
- Feeding a diet that contains excess energy
- Rapid growth
- Physical trauma
- Nutrient imbalances
Signs of wobblers in horses can appear suddenly or have a slow onset.
A diagnosis of CVM can be confirmed with a neurologic examination and diagnostic evaluation completed by a veterinarian. Radiographs of the cervical region are typically taken to confirm damage to the spinal cord.
In some cases, a myelogram may be used as a diagnostic tool. This test is completed while the horse is under general anesthesia.
A myelogram is used to determine if spinal compression is dynamic or static and involves injecting radio-opaque dye near the spinal cord and taking a series of radiographs.
CVM must be distinguished from neurologic diseases such as Equine protozoal myeloencephalitis (EPM), which can cause similar symptoms.
Nutrition and Exercise Management: A diet that provides the correct amount of energy and proper ratios of nutrients is critical for normalizing growth rates to promote bone remodeling in the cervical canal. Exercise may be restricted to prevent injury to the spinal column.
Medication: Osmotic agents and diuretics are administered to reduce swelling in the nerve and brain tissues.
Surgery: Surgical intervention is used to relieve pressure at the site of compression in the spinal column.
Euthanasia: In some cases, euthanasia is an appropriate option for horses with CVM.
6) Scapulohumeral Dysplasia
A condition that affects miniature equine breeds, scapulohumeral dysplasia is a developmental disorder that describes a mismatch in size between the humerus bone and the glenoid socket that holds this bone. 
Scapulohumeral dysplasia results in instability in the shoulder joint and can promote the development of arthritis.
Your veterinarian will conduct a physical exam to confirm a diagnosis of scapulohumeral dysplasia. Radiographs may show osteoarthritis, erosion on the bones of the joint, and variable dislocation of the shoulder joint. 
A bone scan in a horse with scapulohumeral dysplasia may indicate a hot spot in the shoulder joint. 
Prevention of DODs
Horses with signs of a developmental orthopedic disease should be evaluated by a veterinarian. Prompt treatment can help to prevent the condition from worsening.
Proper nutrition should be provided to mares throughout pregnancy and lactation to help prevent developmental orthopedic problems in their foals.
Affected horses should have their nutrition program evaluated by a qualified equine nutritionist and their health monitored by a veterinary professional.
Growing horses need to be fed a balanced diet that restricts excess dietary intake while supplying the recommended amounts of essential nutrients to support bone and joint health.
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