What is the ruling on the congregants praying entirely while seated, even though their only impediment is in prostrating?

If a worshiper is unable to prostrate, he should gesture for it. He must perform whatever he is capable of from standing and bowing. If he is able to stand and bow but unable to prostrate, he is obligated to stand and bow, and then gesture for prostration. If he is unable to bow and prostrate, he should gesture for both. The rule is that the worshiper performs what he is capable of, and what he is unable to do is waived for him. Obligatory prayers are not valid performed while sitting if one is able to stand. As for supererogatory prayers, they are valid performed while sitting, even if one is able to stand.