It is somewhat controversial whether using knee orthosis reduces the mediolateral moment applied to the knee joint or not [5
]. It is expressed by some researchers that the main influence of unloader brace in most cases is compensation for a portion of the external load [5
]. However, the results of this research showed that the adduction moment applied to the knee joint decreased significantly following the use of a new design of knee brace. It is clear that the two important parameters which influence the moment applied on the knee are the magnitude of the mediolateral force and its moment arm. As can be seen from , the mediolateral force decreased following use of the knee orthosis. Moreover, improvement of the knee joint alignment in the mediolateral direction is the other important finding of this research.
The mediolateral force applied to the knee joint decreased significantly (P
value was less than 0.05) with the use of the knee brace in the current research. However, the results of the research undertaken by Schmalz et al. (2011) showed that using the knee orthosis did not influence the adduction force applied to the foot [21
]. In contrast, in the current research, there was an increase in the magnitude of the vertical force, especially in subject 2. Reduction in the valgus angle of the knee joint was interpreted as the main reason for the decrease in the mediolateral loads transmitted through the medial compartment of the knee.
Most studies reported only a few degrees of varus angle reduction during gait [5
]. The results of the current research study also showed that the valgus angle of the knee joint decreased, particularly during the last part of the stance phase. Therefore, it might be concluded that even though the angular change was small, it seems reasonable that the valgus angle reduction would lead to the decreases in the loads transmitted through the knee joint in the mediolateral plane. To the authors' knowledge, the tibiofemoral angle has been measured in some research studies by use of X-ray in a static quiet standing position. However, we measured the angle of the knee joint in the mediolateral direction during walking, which might be a good alternative method in this regard.
The magnitude of orthosis distal migration was not directly measured in this study. It is clear that the congruency of the anatomical and mechanical knee joints influences the performance of the orthosis. If the orthosis migrates distally during walking, it will decrease the knee joint range of motion in the sagittal plane, and the patient will have problems during walking. However, in the current research, the range of motion of the knee joint was nearly the same while walking with and without orthosis. Therefore, it might be indirectly concluded that the distal migration of our new orthosis was not too much to influence the performance of the subject.
The new design of the orthosis might have the following advantages over the other designs.
- It has a modular structure to allow changing the alignment of the components with respect to each other.
- The distal migration of the orthosis is not too much to influence the function of the orthosis.
- The magnitude of the corrective force can be changed according to the patient's needs.
The followings are some limitations of this research study which need to be acknowledged.
- The number of subjects was too limited. It is recommended to evaluate the orthosis on more OA patients.
- The quality of life of the subjects following the use of orthosis was not evaluated.
- The knee joint pain severity was not evaluated.
Finally, it is recommended that other parameters such as stability of the subjects, energy consumption during walking, and severity of the knee pain be measured in future studies.