when treating hemiplegic gait i feel that the problem is not solely spasticity. it is the abnormal alignment and abnormal movement pattern that result from abnormal tone
first,do gait analysis.find out where exactly is the problem.in some patients lack of hip and pelvis control may affect knee control by altering the biomechanics and in some patients even an exaggerated tone in upper extremity could change the total alignment of the body.
divide the gait into stance and swing and do analysis. if you suspect that a particular posture or movementpattern or tone as the problem in that particular position then work on that.for example if the knee hyperextension is due to poor pelvis control with posterior pelvictilt and lack of guteus max strength then work from proximal.
remember in most of the cases lack of proximal control result in abnormal distal movement patterrns.
it is better to reducate in suitable position.some patients may exhibit good knee control in lying but when gravity acts along with body wt in walking we can see the difficulty.
so, determine where to start training.in case of subacute stroke which is progressing well by finding the problem and addressing it will give you nice results. of course for long term cases proper braces are recquired.
personally i recommend you to abnormal gait in book named motor control.and applybobath techinque