There are 134 5-letter words starting with J in the ENABLE dictionary — 2% of all 8,636 words at this length. J is worth 8 points in Scrabble and there is only one of it in the bag, which is why it tends to sit on a rack for several turns. A 5-letter word is usually the fastest way to make it pay rather than keep waiting for a longer one.
The list divides into 6 groups by second letter, the largest being the 32 words with ja. Scanning the right group is faster than reading the whole list, which is why it is broken up below rather than run alphabetically.
If you know more than one letter, this page stops being the fast way to find it. Enter what you have in the unscrambler — the Contains, Starts with and Ends with filters combine, and setting both length fields to 5 narrows this list to the handful your letters actually allow.