Since movement therapy, which can also be used on the non-affected side, is likely to be more effective and less costly, this is what would happen.  As for what is the optimal amount of “rehabbing” from a specific side, there are a variety of theories and opinions on this. In a study of the effects of movement therapy on the function, growth, and development of young children with injuries to the arms and legs, the authors concluded:
Our study identified an interesting interaction between the effects of movement therapy on growth of the injured arm and foot. In general, the lower arm muscles were shown to gain more than the upper arm muscles during the therapeutic treatment, with lower limb activities like standing up or walking gaining more than high limb activities. This indicated that, in this special case, the recovery from damage can also be achieved by movements to a more proximal side of the injured limb, which may be achieved with the use of movement therapy  The use of movement therapy to achieve growth of the arm muscles is known in occupational therapy. As a result of this, it may be possible to achieve a better outcome by using movement therapy to strengthen only one side only . 
The same article summarizes the history of the use of movement therapy for limbs with injuries to different side and points to potential problems. This is also illustrated in a recent article by Chiao Pian, et al. which discusses the issues that arise when using different types of movement therapy.  A common issue identified was that of a “lack of integration”. These two issues do not necessarily mean that all types of movement therapy are ineffective. Movement therapy for children with a loss of arm or leg muscle strength needs to have a mix of therapies in order to achieve results and can often overlap with other types of therapies such as exercise therapy and/or exercise therapy for sports injuries. For instance, although Chiao et al. were not able to determine its effectiveness on a small child, they were able to show that the use of movement therapy was not necessarily limited to the injured arm.  In a recent study, Chiang et al. compared movement therapy and physical therapy for joint injury in children with no limbs. The participants were 6 to 8 years old. They did not make use of any medications or other treatment for the injuries. They were compared with 6 to 8 year old children with limbs that had been amputated or had been affected in one way or another by either motor neuron disease, muscular dystrophy, or myasthenia gravis. The authors concluded from this that exercise therapy should not be dismissed as a treatment. Instead, they recommend its use by the parents and care givers of patients with limb loss to assist them in achieving more favorable outcomes. 
The authors were interested in both the use of muscle strengthening exercises to prevent and reduce the development of weakness and chronic pain in the limbs that arise out of injury.  They also showed that both movement interventions can result in greater functional outcomes and greater physical activity. 
Although studies of the use of movement therapy for limb loss are scanty at present, there is much anecdotal evidence to support the use of movement therapy to treat limb loss. Two cases in which movement therapy and exercise therapy for limb loss were combined have been mentioned previously , and another case of a patient who had an amputation and was using movement therapy was referred by a specialist. The patient was successfully treated and his recovery was reported to have been “almost complete” . 
A recent case report has shown the importance of joint mobility and the use of movement therapy to improve function and function following joint injury, in terms of both recovery and quality of life . This case study involved a 46-year-old woman who was a dual-sport athlete who experienced significant problems with mobility in her left and right arms. The woman’s hand and wrist had been fractured when she was a child and were permanently damaged by her playing sports. One arm was paralyzed, while the other arm was not (as the result of a previous fracture). She started using daily exercises and had many positive results. After two or three months the other arm was working much better and she became a personal trainer. She was able to play at the adult level and had become more social and better with her family. She was using movement therapy alone rather than activity therapy as a result of being able to take this approach. She felt this approach had a positive effect not only on her physical performance of sports but also in her mood. 
As discussed, there is evidence that use of particular therapies for leg pain is associated with less treatment and quality of life, but the literature has been mixed.
The use of specific exercises and the use of movement therapy for the treatment of knee pain is a well-known type of movement therapy. A review of various studies, as indicated earlier, suggests that there is a trend for higher benefits with specific exercise programs than with