How Imaging Supports Diagnosis In Vet Neurology

Introduction

Hip dysplasia is one of the most common orthopaedic conditions affecting dogs and a frequent reason for referral. It is a developmental disorder in which the hip joint that begins with joint instability, which can lead to abnormal bone development around the hip. Over time, this abnormal movement causes damage to the cartilage and bone, resulting in osteoarthritis. Some dogs develop pain while they are still growing, whereas others do not show clinical signs until later in life when arthritis becomes more advanced.

Pathophysiology

The hip is a ball-and-socket joint, formed by the femoral head (ball) and the acetabulum (socket). Normal stability depends on the close fit between these structures, together with support from the joint capsule, surrounding muscles and the ligament of the femoral head.

In dogs with hip dysplasia, excessive joint laxity develops during the first few months of life. This instability allows abnormal movement between the femoral head and acetabulum, disrupting normal joint development. As growth continues, the femoral head often becomes flattened and the acetabulum becomes shallower, resulting in a poorly fitting joint. This altered biomechanics leads to progressive cartilage wear, remodelling of the underlying bone, and ultimately osteoarthritis.

Although hip dysplasia has a strong genetic component, the severity of disease is also influenced by factors such as body weight, growth rate and exercise during development. Although it is not possible to develop hip dysplasia without the genetic potential, not every dog with the genetic potential will develop hip dysplasia.

Also, not every dog with radiographic hip dysplasia develops clinical signs, but those that do generally fall into one of two groups: young dogs with pain associated with joint instability, and middle-aged to older dogs with pain caused predominantly by secondary osteoarthritis.

Signalment and Clinical Presentation

Hip dysplasia is most commonly recognised in medium to large breed dogs, although it can occur in dogs of any size and in cats, especially in pedigree breeds. Clinical signs may first develop between 6 and 12 months of age, particularly in dogs with marked joint laxity. Other dogs remain comfortable when young but gradually develop stiffness and reduced mobility as osteoarthritis progresses later in life.

Owners often describe reluctance to exercise, difficulty rising after rest, reduced willingness to jump into the car or onto furniture, or a “bunny hopping” gait when running. Some dogs become less active or tire more quickly on walks. On examination, discomfort during hip extension, reduced range of motion and muscle loss over the hindquarters may be identified.

Diagnostic Approach

Diagnosis is based on a combination of the clinical history, orthopaedic examination and diagnostic imaging. Perhaps the most useful part of the investigation is feeling and manipulating the hips when the dog is sedated or anaesthetised, as this allows evaluation of joint stability. Radiography is a useful imaging modality and allows assessment of remodelling of the femoral head and acetabulum, and the presence and severity of osteoarthritis.

Advanced imaging such as computed tomography (CT) is not routinely required in every case but may be useful where additional information is needed, particularly if surgical treatment is being considered or concurrent orthopaedic disease is suspected.

As many dogs have radiographic evidence of hip dysplasia without showing pain, imaging findings should always be interpreted alongside the dog’s clinical signs and orthopaedic examination.

Treatment Considerations

Management is tailored to the individual patient and depends on the dog’s age, clinical signs, degree of osteoarthritis and lifestyle. Many dogs benefit from a combination of medical management and weight optimisation, while surgery may provide the best long-term outcome in selected cases.

Surgical Options

Total hip replacement (THR) is considered the treatment of choice for dogs with severe, persistent hip pain that cannot be controlled adequately with medical management. It is most commonly performed in young adult dogs with painful hip dysplasia, although older dogs with advanced osteoarthritis also benefit. Modern hip replacements are designed to provide excellent long-term function and, in most dogs, are expected to last for life. They can be performed successfully in dogs across a wide range of body sizes.

Where total hip replacement is not appropriate, excision arthroplasty (femoral head and neck excision) may be considered. This procedure removes the painful articulation, allowing a functional false joint to develop through the surrounding muscles and soft tissues. Although limb function is generally inferior to that achieved with total hip replacement, many dogs become comfortable and active following rehabilitation.

Medical Management

Medical management forms an important part of treatment for many dogs and may be the primary approach where surgery is not indicated. Maintaining a lean body weight is one of the most important factors influencing long-term comfort and mobility. Exercise is generally modified rather than stopped completely, with an emphasis on regular, controlled activity.

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used for pain relief, while additional medications may be appropriate depending on the individual patient.

Physiotherapy, hydrotherapy and environmental adaptations can also help maintain muscle mass, improve mobility and maximise quality of life.

Prognosis and Long-Term Outlook

Hip dysplasia is a lifelong condition, and osteoarthritis usually progresses to some extent over time. However, many dogs enjoy an excellent quality of life with appropriate management.

The long-term outlook depends on factors including the severity of joint instability, the degree of cartilage damage, body condition and the treatment chosen. Maintaining a lean body weight throughout life is one of the most effective ways of slowing disease progression and preserving mobility. Dogs undergoing total hip replacement generally have an excellent prognosis, while those managed medically often remain comfortable for many years with appropriate monitoring and adjustment of their treatment plan.

Final Thoughts

Hip dysplasia is a common developmental condition that can affect dogs at many stages of life. Early recognition allows treatment to be tailored to the individual patient before irreversible joint damage becomes advanced.

Referral is worth considering where hindlimb lameness persists beyond four to six weeks, where the source of pain is uncertain, or where surgical options such as total hip replacement are being considered. Individual assessment by a Specialist allows the treatment plan to be tailored to both the dog and the owner’s expectations, helping to achieve the best possible long-term outcome.

Hip Dysplasia in Dogs