My question is that is it ok to perform salat(Namaz) in shorts if the length cover the knees.

In the name of Allah, Most Gracious, Most Merciful

Assalaamu `alaykum waRahmatullahi Wabarakatuh

In order for salaah to be valid the satr must be covered. The satr for a male is from the navel till below the knees. This is clearly substantiated in a hadeeth: 

قال النبي صلي الله عليه وسلم :عورة الرجل ما بين سرةه الا ركبته .اخرجه الدار قطني.

(Al Hidaayah V3-4 Pg 460 Shirkat e Ilmiyah)

The shorts covering the knees will fulfil this minimum requirement. However salaah is a means of communication with our creator.  One should adorn such attire that invokes the mercy of Allah Taala.To adorn oneself with the sunnah attire is a mark of respect for Allah Taala.

Therefore to suffice on the shorts is undesirable.

And Allah knows best

Wassalam

Ml. Ebrahim Desai,
Student Darul Iftaa

Checked and Approved by:

Mufti Ebrahim Desai
Darul Iftaa