I Have Had Leg Pain For Almost 5 Yrs. Experienced

I have had leg pain for almost 5 yrs. experienced sharp pain in left knee 5 yrs ago & Drs have not found anything & since have constant ache. Can't bend left leg some days have had X-rays on knees, front of legs, MRI on back( no pinched nerve) No nerve damage, no varicose vein issues. No swelling no arthritis. I'm very frustrated. What's next step???MRI on leg/knee??? Could I have injured something years ago & never healed???