Comparing Local Anesthetic Injections to Nerve Blocks for Pain Control After Total Knee Replacement

Why are we doing this study? People who have knee replacement surgery often feel pain afterward. Doctors use different methods to control this pain. One method is an injection of numbing medicine directly into the knee during surgery, called local infiltration analgesia (LIA). Another method uses a thin tube (catheter) placed near nerves in the leg to continuously deliver numbing medicine, called a nerve block. This study compares these two pain control methods after knee replacement surgery, to find out whether the injection method (LIA) works at least as well as the nerve block method for controlling pain. Who can take part in this study? Adults aged 18 to 90 years who need a first-time (primary) knee replacement because of knee arthritis can take part. Participants must be able to walk before surgery, be in generally stable health, and be able to give informed consent. People with a knee injury (rather than arthritis), people who use a wheelchair, and people unable to give consent were not included. What happens during this study? 78 participants were randomly assigned, like a coin flip, to receive either the injection into the knee (LIA) or the nerve block through a catheter for pain relief after surgery. Both groups also received the same standard pain medicines by mouth or vein as needed. Researchers measured pain levels using a 0-10 pain scale before surgery and at 24, 48, 72, and 96 hours afterward. They also measured knee movement (range of motion), how much extra pain medicine was needed, and how satisfied participants were with their pain control. The study took place at one hospital, the Elisabethinen Hospital in Klagenfurt, Austria, between June 2025 and January 2026.

Inclusion Criteria: * Age 18 to 90 years Primary or secondary knee osteoarthritis (gonarthrosis) Scheduled for elective primary total knee arthroplasty (cruciate-retaining implant) Ambulatory prior to surgery (able to walk unassisted) American Society of Anesthesiologists (ASA) physical status I-III Able to provide written informed consent Exclusion Criteria: * Post-traumatic knee arthropathy (trauma-related indication for surgery) Wheelchair use / inability to ambulate preoperatively ASA physical status IV or higher Lack of capacity to provide informed consent (e.g., legal guardianship/procurator required) Planned unicompartmental (hemi-) knee arthroplasty or revision surgery Known allergy or contraindication to the study medications (ropivacaine, ketorolac, or epinephrine)