Dear fysio:
MSK101 makes some very good points. The joint is mechanical and your expertise is in nerurological. The mechanical aspects are compromised with the PCL restraint gone. The mechanical pressure and vectors of force will be to hyperextend the joint.
You might add to the obvious that your client will have muscle loading and recruitment problems in that the muscles will try to splint or brace the joint. You might consider not just strengthening exercises, but also keeping the proper tonus and balance in the muscles over the joint.
My reference to the hip is that knee problems, ie lack of support, create changes in gait that work themselves through the body in less obvious ways. ( see Hoppenfeld and others.) My reference to the hip assessment is that this should not be overlooked.
Sorry about the negative remarks about my research, but the research has gone beyond me as the OGI, or Ola Grimsby Institute is preparing a research paper on it. I am out of the picture on this as the research is being finished in the USA by another person. The relevance of it to your problem is that it will show if your client is having gait and postural adaptions to his weakened stuctural problem.
Hope this is helpful.
My best to you,
Neuromuscular.