The reasons why the cat is lame and cannot touch the ground with one foot:

1. There may be trauma to the legs or foot pads. You need to clean and disinfect the wound in time, cut off the surrounding hair, and apply anti-inflammatory ointment.

2. It may be that the bones or joints are damaged or fractured. At this time, you need to go to the hospital to take X-rays to determine the damage and take appropriate treatment measures.

3. Pluck the cat's hair. It may be that sharp thorns have stuck in its feet or there are parasite bites. If it is stuck by sharp thorns, it needs to be taken out. If it is bitten by parasites, it needs to be removed. If bitten, apply medicine immediately and do a good job of deworming.

4. It may be that the joint position has shifted abnormally, causing dislocation. You should seek medical treatment as soon as possible. The veterinarian will correct the bone back to its original position after administering appropriate anesthesia.

5. It may be chronic arthritis, which is more common in older or obese dogs. It is necessary to supplement joint nutrition in time. If it is really painful, you may need to take painkillers.