Ultrasound vs. X-ray: When Do We Use Each?

Understanding Diagnostic Imaging in Equine Practice

Two of the most commonly used imaging tools are X-rays and ultrasound. While both are essential for diagnosing injury and illness in horses, they’re used to assess very different types of tissues — and knowing when to use each allows us to make accurate, informed decisions about your horse’s care.

Here’s a breakdown of what each tool does, when we use them, and why it matters.

What Are Radiographs (X-rays)?

X-rays use a small amount of radiation to create images of dense tissues, such as bone.

What X-rays are best for:

Bone injuries (fractures, chips, bone bruising)
Joint conditions (arthritis, OCD, bone cysts)
Hoof balance and conformation
Dental disease
Pre-purchase assessments

Because X-rays show changes in bone density and structure, they’re not suitable for imaging tendons, ligaments, or soft tissue swelling — but they’re ideal for identifying bone abnormalities, even subtle ones.

What Is Ultrasound?

Ultrasound uses high-frequency sound waves to produce real-time images of soft tissue structures. It’s non-invasive, radiation-free, and can be performed repeatedly to monitor healing over time.

What ultrasound is best for:

Tendon and ligament injuries (e.g. SDFT, suspensory ligament)
Joint effusion and inflammation
Reproductive exams
Chest and abdominal imaging
Guided injections or aspiration of fluid
Monitoring healing after injury

Ultrasound excels at showing soft tissue texture, fibre alignment, and fluid-filled structures — but can’t penetrate bone, so it won’t show fractures or deeper bone lesions.

So When Do We Use Each?

Here’s a simple comparison to help:

Condition	X-ray	Ultrasound
Fracture	✅ Yes	❌ No
Arthritis	✅ Yes	❌ No
Tendon injury	❌ No	✅ Yes
Joint swelling	🔄 Sometimes	✅ Yes
Hoof pain	✅ Yes	🔄 Sometimes (for navicular bursa)
Lumps & bumps	❌ No	✅ Yes
Breeding work	❌ No	✅ Yes
Abdominal concerns	❌ No	✅ Yes

In many cases, we use both tools together. For example, if a horse presents with a swollen joint and lameness, X-rays might rule out bone involvement, while ultrasound helps us assess the soft tissue structures around the joint.