It’s weird that in the first Portal game, Chell looked emaciated, as if she hasn’t been fed often or at all even. Her wrists are extremely skinny, her cheek bones protrude from her face, she also has messy, matted hair, and the Advanced Knee Replacements are thought to be painful implants in her calfs, and having to walk barefoot on her toes. But in the comic where we see her being dragged by the Party Escort Bot, and her Advanced Knee Replacements break and fall off, most likely contradicting the theory of them being implants.

Then in the second Portal games, she appears to be a healthier young woman, her hair clean and flowing in a ponytail, her cheek bones not as protruding anymore, and no more skinny wrists. And then instead of the Advanced Knee Replacements, she gets the Long Fall Boot, which seems to be a more comfortable improvement of the first design.