There are some great sites (and YouTube videos) offering information and advice about knee exercises, although they vary quite widely in the content that they cover.
Here is a list of some very good sites that will help the reader to get a good overview of knee rehabilitation exercises and stretches -
A great resource of muscle strengthening exercises for the knee, accompanied by clear and useful explanations and narrated videos. Set up by a senior physiotherapist from the UK.
American Academy of Orthopaedic Surgeons - knee conditioning programme
The first link is to ten printable pages of stretches and strengthening exercises for the knee in .pdf format with clear illustrations, good clear instructions, frequency and repetitions and tips. The second link is less comprehensive, and aimed at knee replacement patients, but the illustrations are good.
A useful resource for patients undergoing total knee replacement, with exercises both before and after surgery. Nice black-and-white photographs and instructions.
Ohio State University Medical Center
Another rehab site aimed at patients with knee replacement, this time focusing on the period after the surgery. The explanations are nice and simple. It is less relevant for younger patients who have had other knee procedures, but the exercises are useful for any knee patient. This is a pdf that looks as though anyone can append it to their website, and in this instance it is appended to the Chester Knee Clinic site.
The Athletic Advisor
The first link is a nice simple and printable aide-memoire with simple illustrations and explanations, but no real context. The second link is to their other set of rehab protocols, aimed at patients who have had a meniscectomy or excision of plica, puts the exercises into context and would be useful for most patients who have had an arthroscopic procedure.
Glasgow Sports Surgery Service
The first link is to a printable .pdf section of their site covering self-treatment of simple knee injuries in the first 48 hours and after, with photographs and explanations of the exercises. The second link is to another printable .pdf, giving a very good overview of ACL issues, including rehab exercises accompanied by photographs and explanations.
Athens Orthopedic Clinic
Six printable pages of simple but clear illustrations of knee rehab exercises, together with explanations.
Sports Injury Clinic
Separate tabbed sections for the different phases of knee rehab. Nice clear photographs but a bit thin on detail.
Why I Exercise
Not really a rehab site, but rather a site for anyone wanting to build up their knee strength. Still, it is very clear and has excellent illustrations.
The Rehab Cycle
Objectives of Rehab
A-Z of Exercises
Ours is a very comprehensive site, with the rehab in three separate sections. The first explains the rehab cycle, and why different exercises are relevant at different stages of rehabilitation after injury or surgery. The second explains what one is trying to achieve during knee rehab. Finally there is a big section of exercises, with explanations, photographs and videos.