Based on the history you provided, below are possible causes for your dog’s weakness. If you still seek further information, please visit our Ask The Vet page to submit a one on one consultation with a licensed veterinarian 24 hours a day, 7 days a week.
Adissons disease
Arthritis
AV block
Diabetes
Intervertebral disc injury
Heart murmur
Hip dysplasia
Hypothyroidism
Intestinal parasites
Medially luxating patella
Myasthenia gravis