Optimising pain relief after knee joint replacement surgery at Counties Manukau Health; We compare two methods of local anaesthesia (numbing medicine) administration to reduce pain after knee replacement surgery.

Knee replacement surgery is very effective at relieving chronic knee pain, but managing pain in the days after the operation is critical for recovery. One approach is an adductor canal catheter — a thin plastic tube placed near the nerve that supplies sensation to the knee — which delivers local anaesthetic continuously to numb the area and reduce reliance on strong opioid painkillers. This trial is comparing two different ways of delivering that local anaesthetic: a slow, constant drip versus larger doses delivered at regular intervals (called programmed intermittent boluses, or PIB). Researchers want to find out which method provides better pain control, results in greater patient satisfaction, and allows people to engage more effectively with physiotherapy and rehabilitation after surgery. You may be eligible if you are scheduled to have a primary total knee replacement at Middlemore Hospital or Manukau Surgical Centre and are between 18 and 80 years of age. People with significant kidney or liver problems, allergies to the study medications, or those on high doses of opioid medications prior to surgery would generally not be eligible.