Panosteitis in dogs – growing pains and lameness

Overview

Panosteitis primarily affects the long bones of the limbs, rather than the joint cartilage.

The typical patient is a young, rapidly growing dog of a large or giant breed.

The condition may affect one bone or several bones at the same time.

Episodes may recur over several months before finally settling.

In a study of 100 dogs published in 1970, 49% had signs in more than one limb.

In the same group, more than one bone was involved in 53%.

Nevertheless, some dogs have only one or a few episodes.

The long-term outlook for panosteitis is generally excellent.

Causes

The exact cause of panosteitis has not been established.

Genetics, rapid growth and feeding are considered possible contributing factors.

Stress, metabolism and immune system function have also been suspected as underlying factors.

Normal fatty tissue in the bone marrow begins to break down.

Connective tissue and new bone gradually form in its place.

The changes may also involve congestion of blood vessels in the marrow.

Pressure within the rigid bone increases as the tissues change.

Irritation of pain-sensitive nerve endings in the periosteum, the bone's outer covering, is the likely mechanism of pain.

With more severe changes, the bone's outer cortex and periosteum may also react.

The bone tissue subsequently remodels back to normal or almost normal.

Bacteria have not been established as a usual cause of the disease.

A bone reaction that looks inflammatory therefore does not automatically mean an infection requiring antibiotics.

Initially, protein-rich fluid may leak from marrow blood vessels into the tissues.

Bone-resorbing cells remove some of the existing bony struts.

New bone with an irregular arrangement initially forms in their place.

During recovery, this bone is replaced by more organised lamellar bone.

Risk factors

The usual age at symptom onset is 5–12 months.

A broader typical age range is 5–16 months.

However, symptoms can begin in a puppy as young as two months.

Panosteitis has also been diagnosed in five-year-old dogs.

Males are estimated to be affected about four times as often as females.

German Shepherds are particularly predisposed.

Other predisposed breeds include Dobermanns, Golden Retrievers, Labrador Retrievers, Great Danes, St Bernards and Basset Hounds.

Small size does not rule out the disease: it occurs in Miniature Schnauzers and Scottish Terriers, for example.

In females, the first episode may coincide with the first season.

In older case series, dogs over two years old were estimated to account for 5–11% of diagnosed cases.

In a veterinary hospital database covering 1994–2004, 70% of panosteitis patients were male.

Males accounted for 48% of all patients in the same database.

In the 1994–2004 veterinary hospital data, small breeds accounted for 1.8% of diagnosed panosteitis cases.

Of the 662 panosteitis patients in that database, 57% were 6–12 months old.

Typical symptoms

Lameness usually begins suddenly without an accident or unusual exercise.

Front-leg signs are estimated to occur about four times as often as back-leg signs.

• Your dog is lame in one leg, or later in a different leg from the previous episode.

• Your dog moves less and avoids normal walks.

• With severe pain, your dog is reluctant to put weight on the leg.

• Appetite decreases during a painful episode.

• Your dog seems tired or apathetic.

• A dog in pain may vocalise more than usual.

• Some dogs have a mild fever.

Lameness can range from barely noticeable to extremely severe.

Rest alone does not necessarily resolve lameness caused by panosteitis.

Weight loss can also occur during episodes.

Pain may become worse over the first few days before the episode settles.

Obvious muscle loss is uncommon in typical, short-lived panosteitis.

Pain may be located in the humerus, ulna or radius, or the femur or tibia.

Complications and consequences

Duration and recurrence of episodes

An individual episode often improves within 2–3 weeks with pain relief and gentle exercise.

An episode involving one bone may also last 2–5 weeks.

A symptom-free period of one month or longer may separate episodes.

Recurrent symptoms can occur until 18–24 months of age.

Episodes may also continue until 2–2.5 years of age.

In some breeds, skeletal maturity is reached at about 12 months.

Episodes generally become less frequent and milder as the dog gets older.

Typical panosteitis does not leave permanent functional impairment.

Recurrence in the same bone is rare, at about 1%, although the same leg may show symptoms again.

Successive episodes in different bones explain why the overall disease period can last longer than a single episode.

Diagnosis at the vet

Investigating lameness

The vet considers the dog's age, breed and previous episodes of lameness shifting between legs.

Tenderness when the shaft of a long bone is palpated is a typical finding.

The examination distinguishes bone pain from pain in surrounding soft tissues.

All joints are examined to identify other orthopaedic conditions.

Alternative diagnoses include elbow and hip dysplasia, and osteochondrosis.

Hypertrophic osteodystrophy and immune-mediated arthritis can also resemble panosteitis.

In an older study, another concurrent orthopaedic condition was found in 26% of dogs with panosteitis.

Blood tests, particularly a blood count, may be used to investigate a general inflammatory response.

The white blood cell count is often normal in panosteitis.

An increase in eosinophils, a type of white blood cell, has been reported in only 1–5% of cases.

A blood count can therefore complement the examination, but does not establish the location of bone changes.

X-rays and follow-up

A typical X-ray finding is patchy increased density in the marrow cavity.

The first changes often concentrate around the bone's nutrient foramen, the opening for its blood vessels.

An early image may be normal because changes only become visible after a delay of 10–14 days.

If necessary, X-rays are repeated after about two weeks.

In an unclear case, repeat imaging may also be carried out after 2–3 weeks.

An image of the painful limb may be compared with the opposite limb to help interpretation.

The severity of imaging changes does not directly reflect pain severity.

Changes during the increased-density phase usually last 4–6 weeks.

The complete cycle of X-ray changes often lasts 60–90 days.

In some dogs, bone changes may take up to 190 days to disappear.

X-ray findings may therefore remain after symptoms have resolved.

Each recurrence of lameness is reassessed when necessary to rule out other conditions.

The earliest X-ray change may also be a local area of reduced bone density before obvious increased density develops.

Later, the marrow's normal pattern of bony struts may be obscured by denser tissue.

New bone on the outer surface has been described in about 15–25% of patients, particularly in more severe cases.

Different bones in the same dog may be at different stages of change simultaneously.

In exceptional circumstances, a bone scan using a radioactive tracer may help if ordinary X-ray changes are not yet visible.

In the older study of 100 dogs, X-ray changes remained very slight in five dogs.

Comprehensive skeletal imaging may identify more affected bones than visible lameness alone would suggest.

Treatment

Pain relief

The main aim of treatment is to reduce pain while the disease settles on its own.

The vet usually prescribes a non-steroidal anti-inflammatory medicine for the symptomatic episode.

More severe pain may require additional pain relief.

If pain is not controlled, the vet may adjust medication according to the dog's response.

Antibiotics have not proved effective as treatment for panosteitis.

Medication for a severely painful episode may include a vet-prescribed opioid.

Exercise and feeding during an episode

Activity is restricted during a painful episode.

As symptoms improve, normal exercise is resumed gradually.

Light to moderate exercise is suitable between episodes.

Avoid strenuous activity and very long walks.

Food for a dog with a poor appetite should be palatable and nutritionally balanced.

Any concurrent orthopaedic condition is treated according to a separate plan.

Concurrent loss of appetite is assessed and treated as a problem in its own right.

Vitamin and mineral supplements have shown only limited results in treating panosteitis itself.

Prevention

Panosteitis cannot be prevented completely because growth and inherited susceptibility contribute to its development.

A complete puppy food formulated for large breeds is suitable for a large-breed puppy.

Do not unnecessarily add calcium, vitamin D or protein to a balanced complete food.

Adjust the amount of food so that the growing puppy stays lean.

In a lean dog, the ribs can be felt beneath a light layer of fat without pressing hard.

At an appropriate body condition, the waist and abdominal tuck are also visible.

Regular, age-appropriate exercise belongs in a puppy's daily routine.

During rapid growth, avoid forced, repetitive impact activity such as long-distance running on hard surfaces.

Do not replace puppy food with adult food simply to reduce protein or calcium without assessing the diet as a whole.

A growing dog eating a low-energy food may need larger portions to meet their energy requirements.

The larger overall amount of food may also increase total protein and calcium intake.

Important for dog owners

Record lameness shifting from one leg to another in a symptom diary, because this helps describe the course of the disease.

Continuous lameness lasting more than 4–5 weeks without improvement raises suspicion of another bone disease.

Unusually severe or atypical symptoms may require further investigations.

There is no need to press firmly on long bones at home, because palpating the bone during examination can itself cause pain.

Also record appetite, general condition and the effect of pain relief. Agree in advance what to do when a new episode begins and when to review whether medication is adequate. Show the practice changes in your dog's gait even if panosteitis has already been diagnosed.

Frequently asked questions

Is panosteitis the same as ordinary growing pains?

Growing pains is an everyday name used for panosteitis. The condition causes pain in the long bones. However, lameness in a young dog may instead be caused by elbow dysplasia or osteochondrosis, for example. Age alone does not determine the cause. X-rays help investigate why the dog is lame.

How long does lameness caused by panosteitis last?

An individual episode often improves within 2–3 weeks. A painful episode involving one bone may also last 2–5 weeks. Episodes can recur over several months as different bones are affected in turn. There may be a gap of about a month between episodes.

Can an X-ray be normal even if a dog has panosteitis?

Yes. X-ray changes may not become visible until 10–14 days after symptoms begin. Imaging is repeated after about two weeks if necessary. Mild imaging changes do not directly mean that pain is mild either. Conversely, changes may still be visible after pain has gone.

Does panosteitis need painkillers if it resolves on its own?

Yes. Pain relief may be needed because an episode can be very painful despite the condition's self-limiting course. The vet usually prescribes a non-steroidal anti-inflammatory medicine. Severe pain may require other pain relief too. Activity is restricted during a painful episode.

Can I walk my dog between episodes?

Light to moderate exercise is generally suitable during periods with fewer symptoms. Avoid strenuous activity and very long walks. During a painful episode, activity is restricted and then increased gradually as the dog's condition improves. Forced long-distance running on hard surfaces is particularly avoided during growth.