That’s a really tough question, because the answer will vary depending on the location and severity of the tear.
If it were me, I’d send the client to a physical therapist first, then ask the client to tell the PT to give you a list of exercises that support the therapy. It’s a great collaboration, something I’m just starting to do with my physical therapist (cross-refer clients).
I definitely agree that you should refer your client to a physical therapist. Knowing wether the tear is partial, complete, medial, or lateral would also help. I personally had a complete tear of the medial meniscus. Partial squats (30% of the normal range of motion) helped me to regain strength and stability.
You do not say whether the client has medical clearance to exercise. And particularly if there are any recommendations on exercise. As there are many factors to consider, I would suggest getting back to us with more information and/or clearance updated information. That the client appears to know they have a torn meniscus tells me that they have seen a doctor. And should have some type of imaging to support the diagnosis. So, getting the physicians input should not be a problem. Also, any history of physical therapy will be helpful. Not to mention that the physician and physical therapist can guide you as well.