I Had A Titanium Rod Put In My Leg (tib/fib)

I had a titanium rod put in my leg (tib/fib) 7 years ago, and for the first 6 everything was fine. I was active and basically painless. Over the past few months the pain has gotten progressively worse, to the point where I lie in bed and it feels like it's on fire. Running, not possible. Walking hurts. Everyday tasks are now difficult. I went and saw my doctor and he has no idea what could be wrong with it. Any ideas?