How was Zhu injured before the Battle of Juxianzhuang in Tianlong Babu?

Zhu sneaked into Shaolin Temple and pretended to be a young monk to steal Yijin Sutra. At Shaolin Temple, he met the abbots of Qiao Feng and Xuan Ci. The abbot of Xuan Ci slapped king kong palm hard on the thrown lantern, and the lantern hit by the palm hit Arju, causing internal injuries. After that, he arrived at Juxian Village with the support of Qiao Feng's internal force, and was accurately judged by Xue Shenyi as being injured by king kong palm.