Legg-Calve-Perthes Disease

TL;DR. Legg-Calve-Perthes disease is a painful condition in young, small-breed dogs where the head of the thigh bone spontaneously loses its blood supply, collapses, and requires surgical treatment to restore pain-free mobility.

Legg-Calve-Perthes disease affects the femoral head—the ball of the hip joint—in young, small-breed dogs.

What is it?

Legg-Calve-Perthes disease, also known as avascular necrosis of the femoral head, is a non-inflammatory, degenerative condition that affects the hip joints of young, small-breed dogs. The hip is a ball-and-socket joint where the top of the thigh bone (the femoral head) fits into the pelvis. In dogs with this condition, the blood supply to this vital portion of the bone is spontaneously interrupted.

Without a consistent blood supply, the bone tissue in the femoral head dies—a process known as ischemia. As the bone degenerates, it loses its structural integrity. Normal daily activities cause tiny cracks, called trabecular microfractures, to develop within the weakened bone. Eventually, the smooth outer layer of the joint (the articular surface) collapses under the dog's weight.

This structural collapse leads to severe joint irregularity, friction, and pain. Over time, the body attempts to heal the damaged joint, resulting in rapid and painful osteoarthritis. Because this process is aseptic, it does not involve any bacterial infection, but it causes significant physical discomfort and progressive lameness.

Causes & risk factors

The precise trigger that causes the blood supply to the femoral head to shut down remains unknown. However, research strongly indicates that genetics play a primary role in the development of Legg-Calve-Perthes disease. It is not caused by trauma, poor nutrition, or active joint infections.

The disease is highly breed-specific, primarily targeting toy, miniature, and small-breed dogs during their rapid growth phase. Symptoms typically begin to emerge when a puppy is between 4 and 12 months of age. Both male and female dogs are affected equally, and while it usually occurs in only one hip, about 10% to 15% of cases involve both hips.

Several breeds have a documented predisposition to this condition. In some, the mode of inheritance has been identified, while in others, it is highly suspected based on clinical frequency.

Signs to watch for

The signs of Legg-Calve-Perthes disease usually develop gradually, starting as a mild favor of one leg and progressing to severe, constant pain. Owners should watch for the following clinical signs:

• Unilateral or bilateral hindlimb lameness (Cardinal): Limping on one or both back legs. This lameness typically starts as a subtle, intermittent limp but steadily progresses to a point where the dog avoids placing any weight on the affected leg.
• Pain on hip extension or abduction (Cardinal): Your dog may cry out, flinch, or attempt to bite when the affected hind leg is gently pulled backward (extended) or moved outward away from the body (abducted).
• Atrophy of the thigh muscles (Common): Because the dog avoids using the painful leg, the muscles of the thigh will rapidly shrink and waste away. When comparing the two thighs, the affected side will feel noticeably thinner and less muscular.
• Crepitus in the hip joint (Occasional): A grinding, clicking, or crackling sensation can sometimes be felt or heard when the hip joint is moved, caused by the rough, collapsed bone surfaces rubbing against each other.

Hindlimb lameness and favoring one leg are cardinal signs of Legg-Calve-Perthes disease.

How vets diagnose it

Your vet will begin with a thorough physical and orthopedic examination. They will watch your dog walk and run to assess the gait, and then carefully palpate the hindlimbs. During this exam, your vet will specifically check for muscle wasting in the thighs, localized pain when manipulating the hip joint, and any grinding sensations within the joint.

The gold standard diagnostic test for Legg-Calve-Perthes disease is pelvic radiography (X-rays). To obtain clear, precise images of the hip joints, your vet may recommend sedating your dog. This ensures your dog remains completely still and comfortable while their hips are positioned for the scan.

On the radiograph, your vet will look for characteristic changes in the femoral head. In the early stages, the bone may appear less dense or patchy. As the disease advances, the X-ray will clearly show flattening, fragmentation, or complete collapse of the femoral head, along with widening of the joint space and secondary signs of osteoarthritis, such as bone spurs.

Treatment options

Conservative medical management is rarely successful on its own because the structural integrity of the bone has already been compromised. However, medical therapies are frequently used to manage pain before surgery or during the recovery phase.

First-Line Medical Management

• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Medications such as carprofen or meloxicam are commonly prescribed to control pain and reduce inflammation within the joint. These medications must only be used under direct veterinary supervision, and regular blood monitoring may be required to ensure your dog's liver and kidneys remain healthy.
• Activity Restriction: Strict crate rest or leash-only walks may be advised temporarily to prevent further microfractures while planning definitive treatment.

Surgical Intervention (Definitive Therapy)

Surgery is the treatment of choice to eliminate the painful bone-on-bone contact and restore mobility.

• Femoral Head and Neck Ostectomy (FHO): This is the most common surgical procedure performed for this condition, especially in small dogs. The surgeon removes the collapsed ball and neck of the thigh bone. Over the following weeks, the dog's body fills the empty space with tough, fibrous scar tissue, creating a "false joint." This false joint prevents painful bone-on-bone rubbing and allows for excellent, pain-free mobility.
• Total Hip Replacement (THR): In some cases, a total hip replacement may be considered. This involves replacing the natural ball and socket with medical-grade prosthetic components. While highly effective, it is technically demanding and typically more costly than an FHO.

Postoperative Physical Rehabilitation

Surgery is only the first step; physical rehabilitation is vital to a successful outcome. Once the painful bone is removed, your dog must be encouraged to use the leg to build up the atrophied thigh muscles and maintain a healthy range of motion in the new joint. Your vet will outline a structured plan that may include controlled leash walks, passive range-of-motion exercises, and professional canine physical therapy.

Prognosis

The long-term prognosis for dogs with Legg-Calve-Perthes disease is excellent following surgical intervention (either FHO or THR) combined with diligent postoperative physical rehabilitation.

Most small dogs adapt remarkably well to an FHO, regaining full, pain-free use of the limb and returning to their normal activity levels. Without surgery, however, the prognosis for comfort and mobility is poor, as the collapsed joint will cause chronic, lifelong pain and progressive, debilitating osteoarthritis.

Prevention

Because Legg-Calve-Perthes disease is an inherited, degenerative condition, there are no lifestyle changes, diets, or joint supplements that can prevent it from developing in a genetically predisposed puppy.

The only effective method of prevention is responsible breeding practices. Dogs that have been diagnosed with Legg-Calve-Perthes disease, as well as their parents and littermates, should be removed from breeding programs to prevent passing the genetic mutation to future generations.

When to call your vet

You should schedule an appointment with your vet if you notice your young dog limping, showing stiffness after resting, or displaying reluctance to jump, climb stairs, or play.

Seek immediate veterinary care if your dog suddenly becomes completely unable to bear weight on a hind leg, displays signs of severe distress (such as panting, shaking, or hiding), or cries out in pain when their hip or hind leg is touched.

For specific breeds

If you own one of the following breeds, you should be especially vigilant for signs of hindlimb lameness during your dog's first year of life:

• West Highland White Terrier: This breed has a proven autosomal recessive genetic inheritance for the disease.
• Manchester Terrier: This breed also has a proven autosomal recessive genetic inheritance.
• Toy Poodle: There is a highly suspected genetic predisposition in this breed.
• Yorkshire Terrier: There is a suspected genetic predisposition in this breed.

Early detection and surgical planning can prevent your puppy from experiencing prolonged joint pain and severe muscle wasting.

Sources

• Standard veterinary orthopedic guidelines and clinical consensus.