I’ve always gotten a medical clearances for people who have known injuries, and a list of limitations. Even though the client often knows, they don’t always know. I also get a list of exercises from the PT,and stick to those. Many people don’t do their PT exercises, so I incorporate them into their training.
Also, remember they still have the majority of their body to work. One know is important, but still leaves you a lot to work with 🙂
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.
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.