Read about Kaposi's sarcoma, a rare type of cancer caused by the human herpesvirus 8 (HHV-8) virus. It affects the skin, mouth and sometimes the internal organs.
Read about keratosis pilaris, which is a common, harmless condition where the skin becomes rough and bumpy, as if covered in permanent goose pimples.
Read about Klinefelter syndrome - a condition in which male babies are born with an extra X chromosome. Find out about the symptoms, causes and treatments.
Sudden knee pain is often caused by overusing the knee or injuring it. Find out what you can do to treat it yourself and when to get medical help.
A person with knock knees (genu valgum) has a large gap between their feet when they're standing with their knees together. It usually corrects itself as a child grows, but sometimes treatment may be needed.
Find out about kwashiorkor, a severe form of malnutrition that most commonly affects children in developing regions of the world where there's a limited food supply.
Kawasaki disease is a condition that mainly affects children under the age of five. It is also known as mucocutaneous lymph node syndrome.
Find out about kidney cancer, including what the symptoms are, how it's treated and what the outlook is.
A kidney infection (pyelonephritis) is a painful and unpleasant illness caused by bacteria travelling from your bladder into one or both of your kidneys.
Information about kidney stones, including symptoms, causes, treatment and prevention.
Read about kidney transplants, including who can have them, what they involve and what the risks are.
Read about how an anterior cruciate ligament (ACL) injury is caused, and the considerations when deciding whether to have reconstructive surgery.
Read about knee replacement surgery (arthroplasty), a procedure to replace a damaged, worn or diseased knee with an artificial joint.
Kyphosis is a condition where the top of the back is excessively curved and appears more rounded than normal.
A knocked-out tooth can usually be saved by putting it back in place or in milk as soon as possible, before seeing a dentist.