Knee biopsy surgery. Arthroscope being inserted into a patient's knee during a biopsy procedure. An arthroscope is a type of endoscope used to look inside joints. It is a minimally-invasive type of surgery (keyhole surgery) that avoids having to open up the whole knee joint. The rod with the lighted tip (lower centre) will also be inserted into the knee, and will send pictures back to the surgeons. They will be able to assess conditions inside the knee, and use surgical tools attached to the arthroscope to take a biopsy (a tissue sample) for further examination. This patient has rheumatoid arthritis, a condition where the body's own immune system attacks the joints and causes damage and inflammation. Photographed in the UK.