1. http://www.youtube.com/watch?v=XlrFc0BYv3U&feature=youtu.be : I personally don’t think that someone with knee pain ( meniscal tear, ACL or any other ligament injury) would be able to activate Quads effectively, especially during initial phases when done with full weight bearing or unsupported. Firstly, patient may not be able to distribute weight equally on both the limbs due to pain and secondly, there may be associated proprioception/balance issues which may result in fall (especially overweight /elderly patients). I would rather choose supported ( e.g. back against a wall) partial knee squats.With wall support patients will be able to distribute weight more effectively, feels more secured and at the same time recruit quads effectively.
Also, quite often during pain patients have a tendency of gaining momentum (finding a rhythm) and there by not activating the quads properly. I think in the video, she needs to extend the knee completely and hold it for 5-6 seconds and slowly release it.
2. http://youtu.be/mxLXKj3BRyA : Is a very good example of active assisted strengthening quads. Caution: too much resistance may aggravate pain.
3. http://youtu.be/d0pEetxHC6A: good demonstration of quad activation with adequate stability.
4. http://www.youtube.com/watch?v=fZspIJrWAgY&feature=youtu.be : very good demonstration of activating all the muscle groups around hip. Caution : with ACL injury, avoid hyperextention (which he does by hyperextending,when he places his leg over the drum ). Also, for hamstring stretch, I would avoid the sitting stretch initially, because alot of us have a tendency of developing thoracic kyphosis ( may lead to postural deformity, i.e. further compensation ) Rather, have the patient lie down, flex the hip at 90 degrees, hold it either with a towel or by hands & extend the knee towards the ceiling and slowly back down towards the surface along with standing calf stretch .
5. http://www.youtube.com/watch?v=rmHKbWKRvFA&feature=youtu.be: Is a good video along with most of the lower limb stretches. Precaution : with sitting hamstring stretch i.e. avoid kyphosis.