SP Case Statement For Adding Innerjoin

I want to add an INNER JOIN based on a condition. If @Sports is not '' then I want to add the inner join statement...

The following doesnt work:

declare @Sports nvarchar(50)
set @sports='1'

SELECT DISTINCT tblUserData.UserName,tblUserData.UserCode,Description,IsDonator,IsVIP,BirthDate,IsMale,ShowAgeOnly,
tblCountries.CountryPicture,
case @LanguageColumnName
 when 'nl' then tblSexuality.nl
 when 'en' then tblSexuality.en
 when 'de' then tblSexuality.de
end
as sexualityname,tblCountries.CountryName,ThumbNailPicture,UserRanking,LastActivityDate,NearestBigCity,DistanceToNearestBigCity,
ROW_NUMBER() OVER (ORDER BY IsVip DESC,UserRanking DESC,LastActivityDate DESC) as RowNum FROM aspnet_Users
INNER JOIN tblUserData ON aspnet_Users.UserId = tblUserData.UserID
INNER JOIN tblCountries ON tblUserData.Country=tblCountries.CountryID
INNER JOIN tblSexuality ON tblUserData.Sexuality=tblSexuality.SexualityID ,
case @Sports
when <>'' INNER JOIN tblUsersAndSports ON tblUserData.UserCode=tblUsersAndSports.UserCode
end