Use a patch that stretches and recovers in the same direction as the knee fabric. A stiff woven backing on stretchy school trackies can make the knee feel tight and push the strain to the edge of the repair. Check the cloth first; some track pants use woven fabric and will need a different approach.
Compare stretch before cutting
Hold a small area of sound trackie fabric across the leg and gently pull it, then let go. Repeat along the leg. Try the candidate patch in both directions, looking at how readily it moves and whether it returns to its original size. Orient the patch so its main stretch follows the garment’s. Choose a similar weight and a smooth surface against the skin. If the surrounding fabric remains baggy or tears under light handling, a patch may have little sound material to hold.
Baste with both layers relaxed
Turn the leg inside out and place the patch behind the hole, covering the area of weak cloth. Let both fabrics rest flat. If you stitch with one stretched and the other relaxed, the knee can ripple once released. Hold the patch with basting or clips you can remove before the needle reaches them. Check that the opposite side of the leg is free.
Use a stitch that can move
If using a machine, check its manual for the needle and stretch stitch appropriate to the knit. A narrow zigzag or the machine’s recommended stretch stitch can allow the repair to flex. Test the combination on comparable scrap first. Stop if the machine skips stitches, damages loops or stretches the test out of shape. Work around the patch on sound cloth, checking the opening stays flat. Add only enough stitching near the hole to control loose edges; a dense, rigid panel may make the knee less comfortable.
Test the movement before school
Pull the repaired fabric lightly in the direction you checked at the start. The stitches should move with it and return flat. Then have the wearer bend the knee and check for rubbing at the patch edge. If the stitches crack or the patch stops the cloth moving, unpick and adjust the stitch or patch choice before wearing.
References
- Brother — needle choice for stretch fabrics
- The Hills Shire Council — clothing and textile repair demonstrations