You probably cannot use the cane or crutch while working as a cook. An employer's obligation is only to make "reasonable accomodations" to your disability, which means changes in process/procedure, or the provision or allowance of assistive devices (such as a cane/crutch) which are not too expensive, too disruptive, or expose the employer to too much potential liability. Using a cane or crutch in a restaurant kitchen is a potential liability risk: not just some risk of contamination from the can/crutch, but also the risk of knocking over hot liquids or oils. It does not seem safe enough to require the employer to do it, though that is just a general response based on what you have written. Since every situation is different and the facts are critical, you should consult with an employment law attorney for more details.