Joint disease can occur even in young animals due to developmental abnormalities. Joint disease is also common in older animals who may develop osteoarthritis where the joints become damaged. 
Help is available in the form of various prescription medications to help pain and inflammation, diets to help and supplements. 
The diets may contain high levels' of' omega-3 fatty acids, glucosamine and chondroitin, antioxidants including vitamin E. 
If you pet is less active, struggles to get up or jump or limps please make a vet appointment for a full assessment. Physiotherapy or hydrotherapy can also help as can providing a soft supportive warm bed, particularly in cold and damp weather.