A high volume injection is performed to treat painful Achilles tendon (Achilles tendinopathy) and patellar tendon (patellar tendinopathy). In chronic stubborn tendon problems, tiny blood vessels grow into the tendon bringing with them new nerves. These nerves are thought to be related to the sensation of pain in the region. The procedure involves injecting a high volume of a solution of normal saline, local anaesthetic and steroid into the space between the tendon sheath and tendon. The solution pushes the tendon sheath away from the tendon and strips off the new blood vessels and nerve endings that have grown into the tendon. The aim of high volume injections is to reduce pain and allow individuals to move and exercise the tendon comfortably. The procedure is conducted under ultrasound guidance meaning that the needle used is directly visualised throughout to ensure accurate needle placement.