How would you know you have a failing hip replacement?

Failing hip surgery: Usually you can tell because after a prolonged period of improved function, you begin having progressive pain on walking. An x-ray will help confirm the diagnosis.

New symptoms: Hip replacements can fail for many reasons, including loosening of the parts, wearing out, muscle dysfunction, or infection. The most likely symptoms would be new pain, increasing weakness, or a leg which is becoming shorter and possibly less stable. Early evaluation of these issues will prevent the problems from progressing and becoming more difficult to treat.