Degenerative Joint Disease

Also known as: DJD — Osteoarthritis — Degenerative Arthritis — Osteroarthrosis

Introduction

DJD in a horse (Image sourced from Bristol Biomed Image Archive with permission)

Degenerative joint disease is the progressive deterioration of articular cartilage and is characterised by hyaline cartilage thinning, joint effusion and periarticular osteophyte formation.

Osteophytes form at the junction between synovium and bone. Joint inflammation leads to the release of factors which drive cells to multiply and differentiate into chondroblasts and osteoblasts. There is matrix deposition, mineralisation and growth of the osteophyte. Mineralised osteophytes develop a trabecular structure and retain a cartilage surface, and when mature may become incorporated into the metaphysis itself.

Chondrocyte necrosis is initiated, degradative enzymes are released and synovitis, continued cartilage degradation and inflammation occur. There is loss of proteoglycans and lubrication in the joint.

Normal joint function is altered by abnormal cartilage congruency and joint capsule anatomy.

Pain, lameness and muscle atrophy develop secondary to joint dysfunction.

DJD is the end-stage to many common diseases of small and large animals and therefore prompt diagnosis and management of these diseases is critical in preventing the condition.

Predisposing Factors

These include any condition causing:

joint trauma: repetitive or acute trauma, intra-articular fractures

joint instability/dysplasia: luxations and subluxations, hip dysplasia, elbow dysplasia, cruciate disease

joint incongruity: conformational abnormalities, congenital malformations, osteochondrosis, Calve Legg-Perthe's Disease

Clinical Signs

These include: lameness, pain, joint swelling, muscle atrophy, pericapsular fibrosis, crepitation and decreased range of motion.

Diagnosis

A history of joint disease is common.

Radiography will reveal: joint effusion, periarticular soft tissue swelling, osteophytosis, enthesitis, subchondral bone sclerosis and narrowed joint space. It is important to note that radiographic changes do not always correlate with clinical signs and not all degenerate joints are associated with lameness.

Arthrocentesis is usually unremarkable, but may reveal slight changes in viscosity, colour and volume.

In horses, less severe cases may require arthroscopy for diagnosis.

Treatment

Treatment should rely principally on rest, controlled exercise and pain relief.

In small animals, an important treatment parameter is weight reduction or control.

Exercise modification/physiotherapy: animals should be put on an appropriate exercise regimen, using analgesia initially and to control flare-ups. Some dogs enjoy hydrotherapy.

Drug therapies: should include NSAIDs and opioids in severe pain. In small animals, example include: carprofen and meloxicam systemically. In horses, systemic phenylbutazone can be given as well as intra-articular injections of steroids, hyaluronic acid and glycosaminoglycans. Corticosteroids should only be given to severe, non-responsive cases and never combined with NSAIDs.

New therapies: acupuncture has become more popular in small animals.

Neutraceuticals such as glycosamide sulphate, chondroitin sulphate and pentosan polysulphate might improve signs, however few controlled studies in dogs and horses are available to support any claims.

Surgical treatment options include:

Joint lavage: minimally invasive and may help remove inflammatory mediators and improve clinical signs for several months

Salvage procedures such as:

Excision arthroplasty: in small animals, for example Femoral Head and Neck Excision

Replacement arthroplasty: total hip replacement and total elbow replacement in dogs

Arthrodesis: in all species depending on the joint, carpal arthrodesis in dogs, pastern and hock joint arthrodesis in horses, fetlock as a last resort.

Amputation in small animals in cases of intractable pain or where financial issues prevent any other treatment.

Ultimately, DJD is an incurable disease and conservative treatment will only slow the progression of the disease.

Prognosis

Prognosis depends on the location and severity of the arthropathy, but is usually guarded for return to athletic function.

Degenerative Joint Disease Learning Resources
Flashcards Test your knowledge using flashcard type questions	Equine Orthopaedics and Rheumatology Q&A 10 Equine Orthopaedics and Rheumatology Q&A 13 Small Animal Orthopaedics Q&A 01

References

Kahn, C. (2005) Merck veterinary manual Merck and co

Corr, S. (2009) Locomotor module: osteoarthritis RVC student notes

Lewis, D. (1998) Small Animal Orthopaedics: self-assessment colour review Manson Publishing

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