When you cut your finger the platelets in your blood clot to form a protective layer around the injury. They also emit growth factors which help heal your cut. Growth Hormone is one of many growth factors that we know.
PRP uses this mechanism for medicine. We take a small amount of your blood and spin it in a centrifuge to separate the platelets and plasma from the red and white blood cells (these are not responsible for healing). After separation the plasma and platelets are treated with light for 10 minutes and injected exactly where your injury is. This helps your body heal in the long term and in a very healthy way.
Conditions that PRP can be used to treat include orthopaedic conditions, osteoarthritis, bursitis, muscle strain, tendinitis and tendinosis.