If you cannot put any weight on an injury, such as if you're recovering from knee or foot surgery, then you'll need one or two crutches (preferably two for improved balance). They'll sustain weight better than canes will, and allow you to get around with only one leg. Most crutches are forearm or underarm crutches. After you've been told by a doctor to use one or the other, the only thing you need to worry about is the fit. For underarm crutches, the top should be an inch or a little more below your armpit and the grips should be even with your hips. Place both crutches on the ground about a foot in front of you, and lean forward slightly. Move as if you're going to step with your injured side, then shift the weight to the crutches and swing forward between them. Come down on your uninjured leg while holding your injured leg elevated so that no pressure is placed on it. Put both crutches together in the hand on your good leg side, like a long and extra sturdy cane. Slowly lower yourself down or up, using the crutches for balance. Start by putting both crutches under one arm, parallel to the floor. Then, you can either hop up or down the stairs on your one good leg, using a banister for assistance. Alternatively, you can lay your crutches down on steps, sit down, and pull them along with you as you use your good leg to sit on the next step.

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Write a summary of the previous text in Chinese:
首先评估你需要多大程度的帮助。 合适的高度。 开始走路。 学习如何坐或拄着拐杖站起来。 学习如何拄着拐杖上下楼梯。