Why do Jack Russells lift one front leg?
It is commonly known as a floating knee. The kneecap moves out of place and causes discomfort for the dog when running. They pull the leg up to prevent discomfort or pain.
How old is my Jack Russell when she breaks her leg?

My jack Russell is five years old. It has never had a health issue. It is female. She has always been physically strong. Today however, she suddenly broke down in the hind leg area. First, her right hind leg was collapsing and was being supported by the left hind leg. As the evening has progressed, both hind legs have given way.
When does Legg lerthes show up in Jack Russells?
Legg Lerthes is a hereditary disease in Jack Russells that often shows up between the ages of 6-12 months and can be corrected surgically. The head of the femur is removed during surgery and the muscles form a false joint for the hip.
Why does my Jack Russell Jump all over the place?

It has an important job. In a normal dog, it is attached above to the main muscle mass at the front of the leg, called the quadriceps, and below by the patellar ligament to the middle of the top of the shin bone or tibia. When the quadriceps muscle contracts, it pulls on the patella which pulls on the tibia and so the leg is straightened.
What are the symptoms of a Jack Russell rupture?
Jacks Russells are prone to developing a cruciate rupture because of their high energy level that leads them to run and jump at every opportunity. Symptoms include: limping, not putting weight on the injured leg, reduction in activity, unusual sitting position and difficulty getting up into a standing position.
My jack Russell is five years old. It has never had a health issue. It is female. She has always been physically strong. Today however, she suddenly broke down in the hind leg area. First, her right hind leg was collapsing and was being supported by the left hind leg. As the evening has progressed, both hind legs have given way.
Jacks Russells are prone to developing a cruciate rupture because of their high energy level that leads them to run and jump at every opportunity. Symptoms include: limping, not putting weight on the injured leg, reduction in activity, unusual sitting position and difficulty getting up into a standing position.
Legg Lerthes is a hereditary disease in Jack Russells that often shows up between the ages of 6-12 months and can be corrected surgically. The head of the femur is removed during surgery and the muscles form a false joint for the hip.
How does wobbler syndrome affect a Jack Russell?
In the most advanced stages, Wobbler syndrome could make it impossible for your Jack Russell to get up, walk or buckle over using their front legs. This stage is usually the onset of paralysis.