campbells7, I mentioned earlier, that it is no surprise that efforts to bring control to your daughter's knee pain by exercising the knee muscles was and will be either a complete or at best, a partial failure. If my original assumptions are true, that is , that she has a common condition known as PFS, then her pain may be of two distinct but linked origins. In the first instance , irritations at the L3 nerve root ( caused , as you will recall ,by protective behaviour there) would give rise to pain in or near the innner aspect of the knee, possibly extending towards the area described as under the knee cap.
The same nerve irritation will lead ultimately to a poor recruitment pattern of the muscle that controls the knee cap during bending , VMO, which will see a worsening of this condition , particularly during effort, such as landing , running, and in extreme cases, walking.
The answers lie not in rest, although it may be said , that a period of no training is of benefit. This is because the nature of spinal protective behaviour, is that it is driven by the ongoing losses of movement that are it's own result. In other words the less you move , the more it holds.
'IT', being the natural non pathological tendency a vertebral spine has , as a feature of it's origins, neuromatrix and essential brain functions, to remain in a pattern of holding, until spinal movements return. It is movement then, of the spine , that has the beneficial effects , that lead to an undoing , as it were, of these normal , ubiquitous behaviours .
I will suggest an exercise that has the potential, to release a certain amount of these protective behaviours.
Done with care , the McKenzie lumbar roll exercise , as I will describe for you, will allow a reduction in paravertebral tone at or near L3. This ought to immediatel;y reduce knee pain, provided, that it is done in a relaxed manner, with no added effects and of course provided that all the foregoing , is as I assert.
Have her lay on a firm warm surface, floor is best. On her back, with knees bent to about 45 degrees. Head supported by a small pillow, abdominal muscles relaxed, head and neck relaxed.
Have her perform a side to side movement of both knees together, such that a gentle pendular swing is maintained at about one swing per second, have her keep this movement going, without any added movements of the upper limbs or head, in a relaxed fashion, no stopping or stretching, for FIVE minutes. This is NOT a stretch, or an activity that requires great effort or any kind of exquisite self control.
Have her repeat this ( Rock and Roll exercise ) two or three times a day.
You will notice, or rather , your daughter will probably notice, that she returns to standing and activity after this with an increased sense of freedom, this includes the knees.
Surgery is an option that ought not to be considered.
PM me and I will direct you further on a method you can easily perform yourself which will have more benefit.
Cheers