Engender a reputation for fragility. Circumstancial evidence, such as a knee support or Band-Aid, can reinforce the deception.
Indicate meekly the suggested area of affliction whilst at the same time remaining as unspecific as possible.
Done well, this technique can waste a lot of time, some of it in a reclined position.
The main problem with feigning injury is that, unlike soccer players or
WWE wrestling stars, most martial artists have a stoic and dignified
attitude to pain and damage. Rolling around on the floor blubbing because
you may have scraped your shin is simply not going to cut it, so you have
to fake a reasonably severe ailment if you are going to waste any time
You should be aware that this technique sometimes fails to work if your partner is a perceptive member of the acting or medical professions. It always fails to work if your partner dislikes you enough that they don't care if you are really injured or not.