When your dog suddenly goes from an obedient pup who sits on command to ignoring the request or struggling to comply, he may be suffering from a hip, joint, leg or anal gland problem that makes it uncomfortable to follow your directives.
Some dog breeds, particularly larger breeds, are prone to hip dysplasia or joint problems such as osteoarthritis. Both can make sitting a difficult, if not impossible, pursuit. If your dog has this condition, in addition to not sitting he likely has a difficult time standing and may walk with a limp. He may also have a noticeable sway in his hips when viewed from behind.
Anal Gland Problems
If your dog has swollen or inflamed anal glands, he likely has a difficult time sitting. Other indicators of this disorder include a red or irritated anal region, a noticeable foul-smelling discharge coming from the area, as well as scooting along the ground, pain with sitting and trouble with defecation. This is an itchy condition, and your dog may lick at the area to try to get relief.
Accident or Injury
Your dog may have trouble sitting if he has an injury due to an accident, fight or even an irritated or infected insect bite. He may have a pulled muscle, a cut, abrasion or painful bruise. Your vet can rule out other more serious possibilities, such as tumor growth.
When to See a Vet
When your dog's behavior suddenly changes and you notice accompanying physical symptoms, it's time to see your vet for an examination. Your vet may be able to assess the problem with a physical exam, or he may require blood tests or X-rays to narrow down the problem. Bone and joint disorders may require surgical correction, or they may be addressed with joint supplements and anti-inflammatory medications. Anal gland problems are typically treated with gland expression and topical or oral antibiotics if infection has set in. Surgery may be recommended in severe and reoccurring cases.