Bone Structure

While overall body shape influences how an animal moves, the underlying skeleton provides the framework that supports every aspect of locomotion, balance and physical function. Bone structure encompasses the size, density, alignment and proportions of the skeleton, all of which contribute to an animal’s ability to perform the physical demands associated with assistance work.

The canine skeleton consists of more than 300 bones connected by joints, ligaments and muscles that work together to produce efficient movement. Well-balanced skeletal structure allows forces to be distributed evenly throughout the body, reducing unnecessary stress on joints and soft tissues during everyday activities.

Different breeds have been selectively developed with varying skeletal characteristics to perform specialised tasks. Sighthounds possess light, streamlined skeletons that maximise speed, while mastiff-type breeds have heavier bone structure that supports strength and stability. Herding breeds typically possess moderate bone density that balances endurance, agility and manoeuvrability.

No skeletal type is inherently superior. Instead, the most appropriate structure depends upon the intended working role and the individual animal’s overall health and welfare.

Heavy-Boned Dogs

Heavy-boned breeds generally possess larger, denser skeletons with broader joints and greater overall body mass.

Examples include:

• Rottweiler
• Newfoundland
• Bernese Mountain Dog
• Mastiff
• Leonberger
• Saint Bernard

These breeds often demonstrate substantial physical strength and stability, making them capable of performing physically demanding tasks where size and strength are advantageous.

However, increased body weight also places greater mechanical loading on joints throughout life. Consequently, heavy-boned breeds have an increased prevalence of orthopaedic conditions including hip dysplasia, elbow dysplasia, cranial cruciate ligament disease and osteoarthritis.

Many giant breeds also have relatively short average lifespans compared with medium-sized breeds, which should be considered when planning long-term assistance animal partnerships.

Light-Boned and Athletic Dogs

Light-boned breeds possess a more refined skeletal structure with comparatively lower body mass.

Examples include:

• Greyhound
• Whippet
• Italian Greyhound
• Vizsla
• Saluki

These breeds generally demonstrate efficient movement, speed and endurance while placing relatively low mechanical stress on the musculoskeletal system.

However, their lighter skeleton and reduced body fat may increase susceptibility to fractures, soft tissue injury and traumatic skin injuries.

Depending on temperament and behavioural characteristics, many athletic breeds can make excellent assistance animals where agility and endurance are beneficial.

Bone Density and Function

Bone density influences the ability of the skeleton to withstand repeated physical loading throughout an animal’s working career.

Animals expected to perform frequent retrieval tasks, accompany handlers over long distances or negotiate varied environments should possess skeletal strength appropriate for their intended workload.

Conversely, excessive body weight without proportional skeletal support may increase the likelihood of injury, while unnecessarily heavy skeletal structure may contribute to reduced endurance.

The objective is therefore not to select the heaviest or lightest animal, but rather one whose skeletal structure appropriately matches its intended working role.

Coat Types

The coat provides protection from environmental conditions while contributing to temperature regulation, skin health and overall comfort. Coat type also influences grooming requirements, maintenance and suitability for different climates.

Although coat characteristics rarely determine whether an animal is suitable for assistance work, they may affect long-term management requirements and should be considered when matching an animal to an individual handler.

Double-Coated Dogs

Double-coated breeds possess two distinct layers of fur:

• a dense insulating undercoat
• a protective outer coat.

Examples include:

• Labrador Retriever
• Golden Retriever
• Border Collie
• German Shepherd Dog
• Siberian Husky

Double coats provide excellent insulation against both cold and heat when properly maintained. Contrary to common misconception, shaving a double-coated dog generally reduces its natural insulation and may increase susceptibility to heat stress and sunburn.

These breeds require regular grooming to remove dead undercoat and minimise matting, particularly during seasonal shedding periods.

Single-Coated Dogs

Single-coated breeds lack a dense insulating undercoat.

Examples include:

• Boxer
• Great Dane
• Maltese

These dogs generally shed less than double-coated breeds but may provide less protection from extreme temperatures.

Depending on climate, additional environmental management may be required to maintain comfort during very hot or cold conditions.

Curly-Coated Dogs

Curly-coated breeds possess continuously growing hair rather than a traditional shedding coat.

Examples include:

• Standard Poodle
• Portuguese Water Dog
• Lagotto Romagnolo

These coats often produce less loose hair in the environment, making them popular with some individuals who have allergies. However, they require routine professional grooming to prevent matting and maintain skin health.

Poor coat maintenance may result in painful matting, restricted movement, skin infections and reduced welfare.

Wire-Coated Dogs

Wire-coated breeds possess coarse outer hairs designed to protect against vegetation and harsh environments.

Examples include:

• Schnauzer
• Wire Fox Terrier
• Airedale Terrier

These coats typically require specialised grooming techniques, including hand stripping in some breeds, to maintain normal coat quality.

Hairless Dogs

Hairless breeds possess little or no protective coat.

Examples include:

• Xoloitzcuintli
• Chinese Crested

While the absence of fur reduces grooming requirements, these breeds require additional protection from sun exposure, cold weather and skin trauma.

Suitability should therefore be considered in relation to the environments in which the animal is expected to work.

Skin

Healthy skin forms the body’s largest protective organ and plays an essential role in immune function, temperature regulation and protection against injury and infection.

Dogs with chronic skin disease may experience discomfort, itching and recurrent infections that reduce their quality of life and ability to work comfortably.

Some breeds are predisposed to:

• allergic dermatitis
• atopic dermatitis
• seborrhoea
• recurrent bacterial infections
• yeast infections
• skin fold dermatitis.

Skin health should therefore be considered alongside overall conformation when selecting prospective assistance animals.

Excessive Skin Folds

Some breeds have been selectively bred to possess prominent skin folds.

Examples include:

• Shar Pei
• English Bulldog
• Bloodhound
• Neapolitan Mastiff

Although these characteristics form part of traditional breed appearance, excessive folds reduce air circulation, trap moisture and create an environment conducive to bacterial and yeast infections.

Repeated skin infections may significantly affect welfare and require lifelong management.

Selection should prioritise healthy skin and functional conformation rather than exaggerated wrinkling.

Tail Structure

The tail is an extension of the vertebral column and plays an important role in balance, movement and communication. During locomotion, the tail assists with stability, particularly when changing direction, climbing uneven terrain or navigating obstacles. It is also one of the dog’s primary methods of communicating emotional state and social intent to both people and other animals.

Tail conformation varies considerably between breeds. While many tail variations have little impact on function, others are associated with inherited spinal abnormalities or chronic health problems that may affect welfare.

Natural Tails

Most dogs are born with a full-length tail consisting of multiple vertebrae.

A natural tail assists with:

• balance during movement
• communication with people and other animals
• body language and emotional expression
• stability during rapid changes in direction.

For assistance dogs working in public environments, clear body language may assist handlers, trainers and members of the public to better interpret the dog’s comfort, confidence and emotional state.

Natural Bobtails

Some breeds naturally possess shortened tails due to inherited genetic mutations.

Examples include:

• Australian Shepherd (Natural Bobtail lines)
• Pembroke Welsh Corgi (some lines)
• Brittany
• Australian Stumpy Tail Cattle Dog

Natural bobtails are not inherently problematic. However, in some breeds the genetic mutation responsible for the shortened tail is associated with congenital spinal abnormalities when inherited in certain combinations.

For this reason, responsible breeding programs undertake appropriate genetic testing and avoid breeding combinations that increase welfare risks.

Docked Tails

Historically, tails were surgically removed from puppies in many working breeds.

Reasons historically given for docking included:

• reducing injury during hunting or herding
• preventing tail damage in dense vegetation
• breed tradition
• cosmetic appearance.

Routine cosmetic tail docking is now prohibited in most Australian jurisdictions except under limited circumstances prescribed by legislation.

While many docked dogs function well throughout life, tail docking permanently removes an important component of canine communication and may slightly alter balance and body language.

Occupational therapists should recognise that many assistance dogs encountered in practice may have naturally short tails or legally docked tails, particularly older animals.

Screw or Corkscrew Tails

Some brachycephalic breeds possess tightly curled or screw-shaped tails.

Examples include:

• English Bulldog
• French Bulldog

These tails are associated with malformed vertebrae and may create deep tail pockets where moisture accumulates.

Affected dogs may develop:

• chronic skin infections
• dermatitis
• pain
• difficulty maintaining hygiene.

In some cases, surgical intervention is required to manage recurrent infections or chronic discomfort.

Ear Conformation

Ear shape varies widely between breeds and influences hearing, ventilation of the ear canal and susceptibility to ear disease.

Ear conformation alone rarely determines suitability for assistance work. However, chronic ear disease may affect comfort, concentration and overall welfare.

Pendulous (Drop) Ears

Pendulous ears hang alongside the head, partially covering the ear canal.

Examples include:

• Cocker Spaniel
• Springer Spaniel
• Basset Hound
• Bloodhound
• Beagle

Reduced air circulation may increase moisture within the ear canal, creating an environment favourable for bacterial and yeast infections.

Dogs with recurrent otitis externa may require lifelong management including routine ear cleaning and veterinary treatment.

With appropriate care, many breeds with pendulous ears successfully perform assistance work.

Erect (Prick) Ears

Erect ears stand upright and allow greater airflow into the ear canal.

Examples include:

• German Shepherd Dog
• Border Collie
• Australian Kelpie
• Siberian Husky

Improved ventilation generally reduces the frequency of chronic ear infections compared with pendulous ears.

However, erect ears remain susceptible to:

• foreign bodies
• traumatic injury
• insect bites
• haematomas following trauma.

Routine veterinary care remains important regardless of ear shape.

Rose Ears

Rose ears fold backwards, exposing part of the ear canal.

Examples include:

• Greyhound
• Whippet

Rose ears are generally not associated with significant inherited disease and usually require no specialised management beyond routine ear care.

Exaggerated Conformation

Over many decades, selective breeding has produced increasingly exaggerated physical characteristics in some breeds. While these features may conform to breed standards or aesthetic preferences, they do not necessarily improve health, function or welfare.

Examples of exaggerated conformation include:

• extremely shortened muzzles
• excessive skin folds
• exaggerated limb shortening
• extreme angulation of the hind limbs
• disproportionately large heads
• excessively heavy body weight.

These exaggerated traits may contribute to chronic pain, impaired movement, breathing difficulties, recurrent skin disease, reduced exercise tolerance and shortened lifespan.

Modern veterinary medicine and animal welfare science increasingly emphasise functional conformation, whereby physical structure should support comfortable movement, normal physiological function and a good quality of life.

For assistance animals, functional ability is considerably more important than breed appearance.

Animals should be capable of performing required tasks comfortably without chronic pain, respiratory compromise or excessive physical strain.

Functional Soundness

While individual conformational characteristics provide useful information, no single feature determines whether an animal is suitable for assistance work.

Instead, assistance animal selection should consider the overall concept of functional soundness.

Functional soundness refers to an animal’s ability to move efficiently, perform required tasks comfortably and maintain good physical health throughout its expected working life.

A functionally sound assistance animal should demonstrate:

• comfortable, pain-free movement
• efficient breathing
• appropriate endurance for its intended role
• good balance and coordination
• freedom from significant conformational abnormalities that compromise welfare
• the ability to safely perform required assistance tasks.

Importantly, functional soundness extends beyond physical appearance. An animal may closely resemble the ideal breed standard yet still be unsuitable because of inherited disease, poor movement or reduced exercise tolerance. Conversely, an animal that differs slightly from traditional breed appearance may possess excellent health, movement and working ability.

Selection decisions should therefore prioritise function over aesthetics.

This principle aligns closely with the welfare-first approach adopted by contemporary assistance animal organisations, which recognise that an animal’s long-term health and wellbeing are fundamental to maintaining a safe and sustainable assistance animal partnership.

Occupational Therapy Considerations

Occupational therapists are not responsible for assessing canine conformation or diagnosing orthopaedic or inherited conditions. However, a foundational understanding of how body structure influences movement, endurance and long-term welfare enables occupational therapists to participate more effectively in interdisciplinary discussions regarding assistance animal selection.

When discussing prospective assistance animals with clients, occupational therapists should encourage decisions based on functional ability, health, temperament and welfare, rather than breed popularity or appearance alone. Appreciating how conformational characteristics may influence an animal’s working capacity also assists occupational therapists to set realistic expectations, facilitate appropriate referrals to qualified assistance animal professionals and veterinarians, and support the development of sustainable human–animal partnerships that prioritise the wellbeing of both members of the team.