Objective: A little bit of weight is tolerated by patellar tendon in trans-tibial hybrid socket, yet. Spandex anti-friction pad consists of two layers of fabric which friction between them is close to zero and therefore it may reduce the pressure to some extent on the patella area. In this study, we are trying to evaluate the effect of spandex anti-friction pad within transtibial hybrid socket design on the amount of the walking ability and satisfaction and reduce pain in patellar tendon area. 
Materials and methods: 16 transtibial amputees, who used the hybrid socket and met the study criteria, with convenience sampling method were entered to study. The variables of the study including duration of standing on the prosthetic leg, duration of walking on the treadmill, pain level (VAS scale) and satisfaction (OPUS) were examined. Then the participants used a spandex pad within their prosthetic sockets for one week and after that the variables of study were evaluated again with previous manner.  The Kolmogroph Smirnoff test for normality of data was used. To analyze the data that had normal distribution (satisfaction and duration of walking on the treadmill) paired T-test and for the data that had not normal distribution (pain and duration of standing on the prosthetic leg), the Wilcoxon test was used. The SPSS software version 26 was used to analyze the data.
Results: The participants showed a significant reduction in pain (p<0.001), and also a significant increase of satisfaction (p<0.001) after one week of using the spandex anti-friction pad. Moreover, the results showed a significant effect on the ability of standing on the prosthetic leg (p<0.001) and the ability to walk on the treadmill (p<0.001).
Conclusion: The results of study showed that the use of spandex anti-friction pad by reducing the pressure and friction between the socket and the stump may reduce pain and increases the satisfaction and comfort for the users of transtibial prosthesis. Therefore, it seems that by using the spandex anti-friction pad, transtibial amputees with patellar tendon pain and problem are able to walk more distance and increases their performance, but more future studies need to confirm it.