Probable Partial ACL Ligament Tear In My Right Knee Joint

In early 2016 I was diagnosed as having a partially torn anterior cruciate ligament (commonly referred to as 'ACL') in my right knee joint. This required 4 months to heal; Surgical intervention wasn't necessary. Two days ago my right knee joint popped - clicked followed by pain. The pain sensation and source of pain in my right knee is identical to the diagnosis last year.

At this point I am honestly lost over what knee specific exercises I can do without causing a complete tear. I have very little mobility and have relied on a power wheelchair since December 2009. When this happened last year the overall instruction was just keep my artificial hip joints moving while this healed. This amounted to very gentle movements in the swimming pool. There are two fitness center machines (hip adduction and hip abduction) which are designed for hip strengthening which should also be suitable for use.