The Islamic Ruling on the Extent of a Man's Awrah (Body to Be Covered)

For a man, from the navel up to the knees is the Satr-eAwrat (i.e. covering of the nakedness) It is in the Hadith Shareef:

(For a man) From below the navel up to the knees is the 'Awrah' (nakedness which needs to be covered). (Sunan Daar Qutni Volume 2 page 160/Chapter of Salaah) It is in Fataawa Shaami:

Translation: And for a man, the Satr-e-Awrat (covering of the nakedness) is below the navel upto the knees i.e. covering this is obligatory. Due to this narration of Sunan Daar Qutni, Satr-e-Awrat is below the navel upto the knees for a man. The knee is included in the Satr but there are two possibilities in this that whether a extremities of the knee is included in that portion which is obligatory to cover, or not.

And the caution is that the knee is part of the Satr. The evidence for this is the narration of Hazrat Ali Radi Allahu Anh that the Holy Prophet صلى الله عليه وسلمsaid, "The knee is an Awrah (nakedness which needs to be covered)" ( Fataawa Shaami Volume 2 page 127/ Zia-ul-Qur'an Publications Lahore) Huzoor Sadrush Shariah Alaihir Rahma writes in Bahaar e Shariat: Satr-e-Awrat (i.e. covering of the nakedness), meaning the essential parts of the body which must be covered is Waajib, be it in Namaaz or outside Namaaz. This applies whether one is alone or in the presence of others. It is even impermissible to reveal the nakedness of the body when alone, without a valid reason. To cover the body i.e. the 'Satr' is Fard, in the case of Namaaz and whilst in the presence of others.(Bahaar e Shariat part 3 page 123/Imam Mustafa Raza Research Centre Overport Durban)

In Summary, For a man, From below the navel up to the knees is the Satr-e-Awrat (nakedness which needs to be covered) therefore wearing short pants that show the knees is Makrooh e Tahreemi (disapproved to the point of being forbidden) according to Shariah.