Re: Post ACL repair... problems straightening knee
Most commonly, inability to straighten the knee is caused by swelling. (Yes, swelling can last years.) Or, there could be a mechanical obstruction. Go to an orthopedist and find out. If it's just swelling or lack of sufficient rehab, you might be able to straighten it out with treatment.
On the other hand, there may be better ways of managing a limited range of motion. I also have trouble straightening my knee sometimes, so I wear a rigid brace with metal. It's a big ugly clunky thing, but somehow it makes my stride more normal and prevents my knee from irritating my back and opposite hip so much.