#abditiveapathy

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Hi!

Without more details like where (rotationally) on the leg this scar is, it's kind of unclear what effect it might have. The knee area, especially on the top and inner side, is pretty bony; some types of scars, if they cause contraction, might affect the ability to bend the knee a little bit, but probably wouldn't cause nerve damage. Honestly, I think tendon damage is probably more likely from a knee injury, especially with more superficial injuries.

Whether crutches or a cane (or one crutch) is a better aid depends mostly on weight bearing ability of the injured leg, and partially on mobility as well.

For single-sided injuries, a cane is a suitable aid if their injured leg can bear at least 75% of their body weight during the part of the walk cycle where the other leg is raised.

Crutches become more suitable when the injured leg cannot properly weight bear. Two crutches can bear up to 100% of a person's body weight, using a three-point gait. A single crutch is technically rated for up to 50% weight bearing, but it can feel insecure or unbalanced, and same as a cane bears a higher risk of stress injury to the weight-bearing wrist or shoulder. So it's often better for unilateral injuries to use two crutches that can each take half the load.

Another thing to consider, especially with nerve damage, is if your character has foot drop, which can happen from pressure on or damage to the peroneal nerve, on the outside of the knee. The hip can accommodate for a lot of knee and ankle problems, but with foot drop, a brace can majorly reduce the strain on the other joints. If the only major symptom of their injury is foot drop, an orthotic brace alone, or a brace and a single cane or crutch, might be the most supportive aids.