Ihad a arthroscopy a year ago and my kne has locked straight its been like it for a week now, it has happened before but was able to unlock in 4 days?

Need to be evaluated: Locking is not normal in any knee. Locking in extension is more likely a knee cap problem, but could be a torn cartilage. You should have this evaluated by the surgeon who performed surgery on your knee a year ago. You may need physical therapy but you may need further surgery. The surgeon knows what's going on in your knee and would have a better idea of what could be causing your problem.