## 4 Discussion  
Evidence from the literature show that balance-specific treatment in elderly subjects undergoing knee replacement had positive effects on proprioception, postural control, balance, and coordination [53]. A meta-analysis showed that balance-specific treatment improves motor performance, i.e., balance and walking, compared to conventional (i.e., non-balance-specific) treatment alone [31]: according to the literature, traditional rehabilitation treatment alone would not be sufficient to improve balance in this type of patient [54]. So far, there is no work in the literature using robotic balance rehabilitation for patients with OA, so it is difficult to compare the results obtained from this study with those already published. Data analysis reported that patients undergoing balance-specific treatment with the Hunova(r) showed a significant improvement in dynamic balance and walking, both in terms of walking speed and distance travelled, compared to the group of patients undergoing conventional rehabilitation alone. These data were also confirmed by the results of the instrumental assessment, especially in its dynamic component. In this case, data analysis showed a marked improvement in dynamic balance in the group of patients undergoing rehabilitation with Hunova(r), both compared to baseline and, for some specific parameters, compared to the conventional rehabilitation group. In the latter case, in fact, patients in the Hunova(r) group showed a significant improvement, especially in the reduction of swaying, the reduction of swaying, and the reduction of trunk movements. These results could be due to the fact that through the use of Hunova(r), intervention training based on perturbation, proprioception, and load perception was more effective than conventional rehabilitation intervention alone. The analysis of the results revealed two other interesting things: the first is that patients undergoing a hip replacement and rehabilitation with Hunova(r) showed a significant improvement in symptoms, pain, quality of life, and overall treatment efficacy compared to the group of patients undergoing the same surgery and conventional rehabilitation alone. The second is that when considering fatigue, patients in the Hunova(r) group showed a significant reduction in fatigue in both the motor and cognitive components. These results confirm what [PERSON] and colleagues [55] have already showed, albeit in a different population undergoing robotic rehabilitation with Hunova(r). This study showed that elderly patients who underwent prosthetic hip and knee replacement surgery had a significant improvement in terms of not only walking but also in the reduction of postural oscillations, and consequently showed greater stability during dynamic balance. These elements leading to improved balance performance and a reduced risk of falling. Furthermore, this study shows that fatigue, which can be a contributing factor to falls in elderly subjects, is also reduced in those patients who have undergone specific treatment for balance disorders with the Hunova(r) platform. Several studies have reported that a specific rehabilitation treatment for balance and walking is effective in patients underwent surgery after OA [17; 18; 31; 33]. To the best of our knowledge, to treat those patients, beyond conventional physical therapy, technological rehabilitation is carried out mainly by means of end-effectors and exoskeletons [25; 26; 27; 28]. Some aspects need to be taken into account while analyzing these findings. First of all, because these are preliminary findings, further research will be required to validate the original theory. The sample size is the study's primary limitation. However, as previously mentioned, the [PERSON] rules for Pilot Clinical Trials [51] were used to estimate the inclusion of 12 patients each group, for a total population of 24 people. A further constraint on the research is the absence of post-protocol and post-discharge follow-up.