As-salamualaikum. One male can't fold his right knee ( Right hip & Knee joints fractured in accident). He desires to join Jumma prayer. How he can join? If, sitting on a chair, where to place the chair. What would be the flashing of the chair with the line of Jamat?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The one who prays sitting on a chair is of two types:

The first type: the one who prays sitting on the chair from the beginning of the prayer to its end; such a person should make his backside when sitting on the chair aligned with the row whether the legs of the chair become a bit forward or a bit backward. Indeed, the scholars stated that what matters about the place of the person led in prayer and who is sitting is his sitting position. The Fiqh encyclopedia reads: “What should be taken into account in being forward or backward for a person who is standing in the prayer is (the position of) his heel and not his ankle, and what should be taken into account in regard to the person who is sitting is (the position of) his backside.”

Indeed, Shaykh Ibn Uthaymeen was asked about someone who prays in the mosque on a chair, would he make the rear legs of the chair aligned with the legs of the congregation, or does he make the front legs of the chair aligned with the legs of the congregation? He replied: “He should make the rear legs of the chair aligned with the legs of the congregation.” He was told: “But if this is the case, when he stands he would be ahead of the row?” He said: "He is not standing, so he should make his backside aligned with the legs of the congregation...” Of course, the statement of the Shaykh applies to the one who prays sitting all along the prayer.

The second type: the one who prays standing but he will sit when bowing down and when prostrating. We have not come across any statement of the former jurists about the position of the praying person in such a case; however, Shaykh Abdur-Rahmaan Al-Barraak was asked about this and he said: "What should be taken into account here is the standing position, so he should be level with the row when standing. In this case, the chair will be behind the row, and it should be placed in such a manner that does not disturb the praying people in the row behind."

It should be noted that a person who has a sound reason for not standing in the prayer and prays while sitting on a chair, then this excuse does not make it permissible for him to sit on the chair and lean forward for bowing down [Ruku’] and prostrating [Sujood] if he is able to perform them, and if he has a sound reason for not performing Ruku’ and Sujood in a proper manner, then this excuse does not make it permissible for him to leave standing and sit on the chair if he is able to stand. The rule about the pillars of the prayer and its conditions is that what a praying person is able to do, he is obligated to do it and what he is unable to do, he is exempted from doing it.

Therefore, if someone is unable to stand, he is permitted to sit on a chair during the standing position of the congregation and he should perform Ruku’ and Sujud in the proper manner, and if he can stand but it is difficult for him to perform Ruku’ and Sujood, then he should pray standing and then sit on the chair when performing Ruku’ and Sujood, but he should make the prostration lower than the bowing.

Allaah Knows best.