The common term for this is “rotundity”, also known as “O-shaped leg”. In medical terms, this is called “inversion of the knee joint”. This is an advanced result of osteoarthritis of the knee joint. It used to be difficult to treat, but now it can be completely cured with an artificial knee replacement.
The patient was 62 years old, had osteoarthritis in both knees for more than 10 years, and had an inversion deformity (rotundity).
This is a comparison of 2 years before and after surgery, and it is completely normal.