Hi,
Muscle tears, sprains, and strains: Pain, heat and swelling are usually seen at the sight of the injury. This is usually close to, but not involving, a joint. Muscle spasms are also commonly present. The diagnosis is made by ruling out joint disease and ligament tears.
Rheumatoid arthritis is not as common but still an important cause of lameness in dogs. In this disease, the immune system mistakenly attacks joints causing pain and may lead to destruction of the joints. In Erosive Rheumatoid Arthritis, the targeted tissue is cartilage, the bone beneath the cartilage, and the ligaments or tendons. There is no cure, but treatment may result in remission of signs. Toy and small breed dogs are more susceptible. Signs usually include joint swelling, a lameness that shifts from leg to leg, muscle spasms and episodes of fever or lethargy. This may progress to deformities of the joints affected.
I would talk to your vet and ask him about running some tests to determine the cause. You can try massaging the legs after a episode or using warm compresses to alleviate some of the pain. If you notice it happens more frequently when it rains massaging the affected area's prior to the spasm coming on may prevent it or cut down on the severity of the issue. I would also let the vet know when the problem is at it's worst.
Walter
Breeder
Breeder and pet health consultant. Have spent a number of years with dog rescue, training and health