- Klinefelter's syndrome 758.7
- Klinger's disease 446.4
- Klippel's disease 723.8
- Klippel-Feil disease or syndrome (brevicollis) 756.16
- Klippel-Trenaunay syndrome 759.89
- Klumpke (-Déjérine) palsy, paralysis (birth) (newborn) 767.6
- Klüver-Bucy (-Terzian) syndrome 310.0
- Knee - see condition
- Knifegrinders' rot (see also Tuberculosis) 011.4
- Knock-knee (acquired) 736.41
- Knot
- Knots, surfer 919.8
- Knotting (of)
- Knuckle pads (Garrod's) 728.79
- Köbner's disease (epidermolysis bullosa) 757.39
- Koch's
- Koch-Weeks conjunctivitis 372.03
- Koenig-Wichman disease (pemphigus) 694.4
- Köhler's disease (osteochondrosis) 732.5
- Köhler-Mouchet disease (osteoarthrosis juvenilis) 732.5
- Köhler-Pellegrini-Stieda disease or syndrome (calcification, knee joint) 726.62
- Koilonychia 703.8