This is nice generic advice Elaine but given a high amount of meniscus tear have concomitant tears of the ligaments it would not be appropriate to do planks due to the shearing knee forces involved.

If your looking for a rehab approach I would be working on counter acting hip antro version and ankle inversion/ over pronation. This is what Elaine is pertaining to I believe.

However locking of the knee is synonymous with a loose body and this can grate against your cartalige generating further pain and damage.

A good practitioner will refer for imagery before boldly pushing you into further direct rehab of the knee.

The approach of supporting the ankle and core certainly does get round this issue.

But my advice to a body builder like you is to stop squats with weight until the structural issue is quantified.

Good luck