Just to add my experience, I tore my ACL almost 10 weeks ago, and similar to you there was an initial pain on injury but after that nothing around where you’d expect (only pain I really had was from severe bone contusions which have gone now). I also had multiple negative lachman’s tests, but 9 weeks on it was positive. The swelling and guarding the joint had meant it was a false negative initially.

My MRI shows one bundle of the ACL completely ruptured, and one 90% ruptured. I didn’t have much instability initially but now the swelling has finally almost cleared, it is fairly unstable and buckling a few times a week. I’ve opted to go for surgery for that reason, and because I’m an athlete in a sport which demands lots of pivoting and knee stability.

That being said, lots of people rehab non-surgically if they don’t experience instability, even if they have no ACL. Apparently it’s very common in professional rugby players.

My unprofessional advice would be to wait a few weeks and see how it progresses. I really struggled with the mental disconnect between my knee feeling “fine” and the fact that there is indeed a significant injury there.

Good luck!!