The name Leg of Mutton ( or leg ‘o’ mutton ) is the best indication as to what kind of sleeve this is. When fully drafted and sewn, it looks like you have a leg of mutton on your arm. The sleeve has a lot of fullness at the top but when it reaches the hem it is tighter than a normal sleeve hem, which gives it the resemblance to a sumptuous mutton leg. Usually, this is a long sleeve and the tightness can be seen from the elbow to the wrist.
“Sleeve with full top gathered or pleated into armhole and tapered to wrist where it looks like a regular sleeve. Size may vary-in 1895, very full sleeve requiring a yard or two of fabric were popular”. The Fairchild Books: Dictionary of Fashion
The leg of Mutton sleeve was a very prevalent fashion seen in clothes in the 19th century and around. Check out this page for some pictures of this sleeve in action in the fashion of those times.
The puff at the top of the sleeves can have varying degrees of pronunciation depending on the fashion and the figure of the wearer. The top puff was a lot pronounced in earlier fashion than in modern fashion. This full-on fullness was maintained with a lot of external aids like netting, stiff lining etc inside the sleeves. The voluminous top portion was maintained also with stiff horsehair fabric inside. The attractiveness of this fashion was that the voluminous sleeves when combined with a full skirt, made the corseted waists of the ladies appear thinner.
In its modern avatar, it is more streamlined and looks more like the leg of a lamb or even a chicken. This toned down version can be used to great effect on jackets, blouses, low cut gowns etc
Leg of Mutton Sleeve
This sleeve can be designed in two ways: One is the traditional way of having two parts to the sleeve. The top sleeve which ends at the elbows is joined to a separate tightly fitting sleeve portion from elbow to wrist. The other sleeve is in one portion and this is the one described in this pattern tutorial
To draft this sweet sleeve which if designed rightly can look good on kids frocks and tops for adults you will have to take a fabric folded diagonally ie the leg of mutton sleeve is better cut on a bias cloth.
Mark an ordinary sleeve pattern on a paper.
Make a straight line 1″ below the armline of the sleeve and then make a line perpendicular to it from the center of the top edge of the sleeve.
Cut it out. Keep this pattern on another new pattern paper. Open it out and spread it as shown in the picture below – this depends on how much gathers you want.
Draw your new sleeve with this new dimension.
Here is your new Leg of mutton sleeve
Keep your fabric pieces for the sleeves right sides together
Place this paper pattern on the fabric so that it is kept on the bias grain of the fabric.
Mark this new pattern. Make a mark at the center of the top edge – you can clip this – you want this to align this point with the shoulder seam when you stitch the seam
To stitch this new sleeve finish the hem and finish the edges of the top edges with a serger if you want to.
Gather the top edge at the sleeve head with basting stitches. Make two lines of basting stitches for better accuracy.
Keep it right sides down on the shoulder seam, aligning the clip you made earlier with the shoulder seam. Carefully start stitching from the center to both sides of the sleeve top edge. Sew the side seam
A lot more about the Leg of Mutton sleeve can be read here – though it is mentioned by another name Gigot sleeve