What causes a femur fracture to move once in a cast?

Needs immediate eval: Call the Ortho doctor's office and discuss your concern with them. There may be an error with the the cast itself or you may have misunderstood the instruction given for home care.

Movement: Fractures can move/shift in a cast for many reasons, but the most common reason is that the swelling has gone down. This causes the limb to be "smaller" in the cast, which allows too much room to move around. For this reason, casts are often changed every 2-3 weeks until the fracture has healed.