You have 3 options available to you.
The 1st option is to knit plain stocking stictch socks. This means just knitting around and around and around until you have your required number of rows. If your X number is 16 you can make shorter socks by doing 3X rows (48 rows) or ‘normal’ 4X (64 rows). The above and below socks have both been done using 4X rows.
Option 2 is a rib at the back of the leg. This pattern puts 3 2×2 ribs down the back centre of the leg. As it is easier to start on the knit stitch it will look uneven as you knit it but it WILL end up as the central 3 ribs going down the middle.
Needle 1: K2, P2, K2, P2, Knit to end.
Needle 2: Knit all.
Needle 3: Knit all.
Needle 4: Knit to last 6 stitches, P2, K2, P2.
Knit this pattern around and around and around. If you have a small thin stitch marker (or tie a piece of string as a marker) it is a good idea to place one before you start the ribbing on needle 4- many a time I forgot to do the ribbing and had to go back and do the last stitches again.
Option 3 is a ribbing pattern I am going to try on my socks. I am going to start with 5 2×2 ribs down the back centre of the leg and as I work my way through each X stop them so at Row 17 I will go to 3 2×2 ribs, at Row 33 1 2×2 Ribs then at Row 49 I am undecided whether to continue with 1 2×2 Rib or go to no ribbing.
Therefore Row 1-16 will be Needle 1: K2, P2, K2, P2, K2, P2, K to end.
Needle 4 will be: K till last 10 stitches, P2, K2, P2, K2, P2.
Rows 17-32 will be the same as Option 2.
Rows 33-48 will be N1: K2, P2, Knit to end. N4: Knit to last 2 sts, P2.
Row 49-64 will be either Knit all stitches or same as Rows 33-48.
If you have a different X (not 16) and you would like some help with option 3 please let me know.
Decreasing- When your calf is bigger than your ankle.
My calf is larger than my ankle and foot. To make sure the sock fits around the ankle and is not baggy I will need to decrease from my 72 stitches (X = 18) cuff down to 64 stitches (X = 16). This means I need to decrease 8 stitches. If you need to do this I would recommend doing it in the following way:
Option 1– at halfway through each of the X sections – ie rows 9, 25, 41, 57. (for X=16).
I would start at needle one with a Knit 2 Together (K2Tog)(Video) and end needle 4 with a Slip, Slip, Knit (SSK)(video).
For Option 2– Use the same rows as Option 1.
For Needle 1: K2, P2, K2, P2, K2Tog, Knit to end.
For Needle 4: Knit till 8 Stitches left on needle SSK, P2, K2, P2.
For Option 3 we will probably use the same method as Option 2 but as I have not knitted this option before will may have to edit this text!