Table 7 Eligibility criteria for dogs to be enrolled in the study

Inclusion criteria

- Age ≥ 12 months

- Body weight ≥ 8 kg and ≤ 60 kg

- Clinical and radiological diagnosis of OA

- OA pain lasting ≥ 3 months

- Pain severity > 11 on HCPI

- At least two of the following HCPI items being described as “difficult” or “very difficult” by the owner (i.e., scored 3 or over): items 5, 7, 8 and 9, corresponding to the ability to trot (5), jump (e.g., in car, on sofa, 7,), lie down (8) and rise from a lying position (9)

- Pain on palpation or lameness being scored > 1 (each on a 0–4 scale) by the veterinary surgeon

- Stable home environment and lifestyle (including physical activity level) throughout the study

- Owner ensured that the same family member was to take the dog to each visit and answered the telephone questionnaire each time

Exclusion criteria

- Persistent or chronic pain due to any cause different from OA (e.g., cancer, neurological disorder)

- Any concurrent disorder interfering with dog’s locomotion, muscle function, physical activity or quality of life (e.g., hypothyroidism, hypo-/hyperadrenocorticism, electrolyte disturbance)

- Contraindications to the use of NSAIDs

- Pregnant or lactating dogs

- Long-acting steroids within 8 weeks before study entry

- Either oral/parenteral steroids or analgesics (e.g., gabapentin, amantadine, SSRIs) within 4 weeks before study entry

- NSAIDs the week before study entry

- Any concurrent treatment (including physical rehabilitation)

- Any surgery less than 12 months prior to the study