Two years ago I tore my ACL and meniscus. There are a few different grades of it and will require different procedures, but until the surgery(if necessary) he will be able to walk normally. The way I see it, there are 3 likely outcomes.
1. It is a relatively minor mensicus tear and does not require surgery, just rehab. This is generally unlikely just because the meniscus doesn't get a lot of blood flow which causes it to be very slow to heal something like this.
2. A small tear, which would require either a minor repair or a partial meniscectomy. The minor repair is what I had, just a single stitch to help it heal together appropriately. That would probably be 2-3 weeks of light work until he can start training fully. A partial meniscectomy requires more time to heal and would be more like 6-12, as well as we would see him in a brace to keep him from bending his knee at all to allow it to heal without the pressure that a bent knee would exert on the meniscus.
3. A large tear which requires significant action to fix. This is a 12 week recovery, just a more invasive and significant repair than the small tear mentioned above, also in a locked-out knee brace.
Scenario 2 is most likely but with our luck it will be 3. No way to tell without a scan. Also, I am not a doctor, just someone with a screwed up knee who has done a lot of research on it.