Osteoarthritis

Dogs show joint pain, lameness and reduced activity and mobility, graded from mild to severe clinical stages. The clinical picture is built from an owner questionnaire, observation of posture and gait, and hands-on palpation and manipulation of the joints, then confirmed by radiography, which also reveals underlying developmental disease. Radiographic changes correlate poorly with pain and function. In cats lameness is uncommon; signs develop gradually and are subtle and non-specific, so owners and veterinarians often attribute them to ageing. In horses osteoarthritis presents as lameness in athletic or older animals.

Osteoarthritis is a progressive, degenerative disease of synovial joints, not an infection. Once described as non-inflammatory, it is now understood to involve low-grade chronic inflammation of the cartilage, subchondral bone and synovium. In the joint, pro-inflammatory cytokines such as IL-1 beta and TNF-alpha, raised in synovial fluid, synovial membrane, cartilage and bone, drive synovitis and cause chondrocytes to release matrix metalloproteinases, aggrecanases, reactive oxygen species and prostaglandins that break down cartilage matrix. The joint deteriorates structurally, with articular cartilage loss, osteophyte formation and periarticular tissue change. Persistent pain can lead to peripheral and central sensitisation, affecting mood, sleep and cognition. In dogs most cases are secondary to an earlier joint disorder or injury.

In dogs, osteoarthritis is reported in about 20% of dogs over one year of age in North America, while UK primary-care estimates range from 2.5-6.6% of all dogs to 20% of dogs over a year old. Secondary osteoarthritis is the most common form, often starting early in life from developmental disease such as hip or elbow dysplasia or osteochondritis dissecans, from cranial cruciate ligament disease, patellar luxation or joint trauma. Reported risk factors include higher body weight, neutering, breed (for example Rottweilers and Golden Retrievers), age, unrestricted feeding and certain exercise patterns. Radiographic osteoarthritis is estimated in 90% of cats over 12 years old. In horses it causes up to 60% of lameness cases.

The main alternatives in a dog with joint pain are septic arthritis and immune-mediated arthritis. Both are suppurative, with many neutrophils in synovial fluid and a marked rise in serum C-reactive protein, whereas osteoarthritic joints have no increase in synovial neutrophils and serum CRP is not raised. Radiography identifies developmental joint disease, and further imaging such as arthroscopy, CT or MRI is used to exclude other joint pathology before the diagnosis is confirmed.

Synovial joints: articular cartilage, subchondral bone, synovial membrane and fluid, periarticular tissues; commonly hip, elbow and stifle in dogs

Keep optimal body weight and condition, avoid unrestricted feeding and monitor growth in young dogs, give age- and breed-appropriate exercise avoiding excessive high-impact loading, assess at-risk young dogs, consider preventive surgery.

Incurable and progressive; care aims to limit pain, mobility loss and poor quality of life. Stage-based long-term management gives functional improvement, and total hip replacement gives excellent outcomes in most suitable dogs.