Based on the history you provided, below are possible causes for your dog’s weakness. Not listed here but a necessary consideration as a possible cause for generalized weakness with pain at this advanced age, is systemic cancer. 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.
Arthritis
Hip dysplasia
Intervertebral disc injury
Medially luxating patella
Cranial Cruciate Ligament Rupture
Older female dog lethargic and when up walking walks in circles to the right