Find the working area
Turn the sleeve inside out and feel for thinning beyond the hole. Mark the full weak zone while the sleeve is relaxed, then add enough patch margin to reach stable cloth.
Keep the patch clear of the seam and allow it to follow the sleeve’s shape. A square placed across a curved elbow may create unnecessary folds.
Choose a flexible pattern
Open grids, parallel rows and simple repeated motifs can reinforce an elbow without packing the fabric too tightly. Keep the stitch field broad enough to share movement.
Use a thread and needle that pass through the sleeve without excessive drag. Test the bend after a few rows instead of waiting until the patch is complete.
Finish for wear
Secure the patch edges and inspect the inside for catches that could irritate the arm. The reverse should be tidy enough to survive normal dressing and washing.
Wash gently according to the garment and patch instructions, then flex the sleeve again. A repair that remains comfortable is more useful than one that only looks strong when flat.