Because of the hot weather, we have taken shorter walks lately, which could be a good chance for Penny to rest a sore limb.
When I went out with her yesterday, I think I finally established that she is nodding her head as she steps on her left front leg, which would mean the pain is in the right front leg, according to this site.
Usually a dog will come down heavier on his healthy limb and avoid putting substantial weight on the limb that is bothering him. You can identify this by observing your dog's head when he walks. The comfortable limb will be placed on the ground and his head will go down at the same time. His head will tend to come up when the uncomfortable limb is on the ground.
She'll go to one of our favourite swimming spots, today, because in the water she can exercise without stressing a sore limb.
When she comes home, we'll examine her nails and see if they are longer on one leg, because on this site I read:
Pets with rear leg pain often cary those legs father forward than normal and their hip on the affected side a bit higher. Pets with front led pain are often reluctant to move. When pets favor a leg over time, the toenails on that limb tend to be longer than on the others. That may be enough to identify the limb that is causing its abnormal walk.
Penny is still keen to go for walks and hurries in and out to the backyard when we go outside. She's been chasing toys in the park eagerly for the last few months, a practice we cut back after her surgery for a cruciate tear four years ago. (We throw the toy only a short distance, and along the ground, so that she runs straight with no swerving or sudden stops.)
She's been taking daily doses of Glyde joint supplement for eight years, so here's hoping the limp is only a temporary problem. A friend suggested that sometimes it's a good idea to give a dog a course of pain relief for a week and see if her behaviour changes. If the limp doesn't go away, we'll go to the vet and discuss options.