Total knee arthroplasty (TKA) is frequently associated with significant postoperative pain, which may delay early mobilization and negatively affect functional recovery. Peripheral nerve blocks are widely used as part of multimodal analgesia strategies to improve postoperative pain control while minimizing opioid consumption and preserving motor function. Different peripheral nerve block techniques may result in varying analgesic efficacy and mobilization outcomes.

The aim of this prospective observational study is to compare the effects of commonly used peripheral nerve block techniques on postoperative pain control and early mobilization in patients undergoing total knee arthroplasty under spinal anesthesia. Patients receiving fascia iliaca plane block are compared with those receiving a combination of adductor canal block and interspace between the popliteal artery and capsule of the knee (IPACK) block.

The primary outcome is postoperative opioid consumption within the first 24 hours after surgery. Secondary outcomes include postoperative pain scores assessed at predefined time intervals, early mobilization parameters, and opioid-related adverse effects. The findings of this study are intended to contribute to optimizing analgesic strategies and improving early functional recovery following total knee arthroplasty.

Total knee arthroplasty (TKA) is a commonly performed orthopedic procedure associated with moderate to severe postoperative pain that may impair early mobilization and delay rehabilitation. Effective postoperative analgesia is essential to facilitate early functional recovery, reduce opioid consumption, and minimize postoperative complications. Multimodal analgesia strategies incorporating peripheral nerve blocks have become increasingly important in postoperative pain management following TKA.

Peripheral nerve block techniques aim to provide effective analgesia while preserving motor function to support early ambulation. Traditional proximal blocks may provide adequate pain relief but can be associated with motor weakness that limits mobilization. More distal techniques, such as the adductor canal block, are increasingly preferred due to their motor-sparing characteristics. The interspace between the popliteal artery and capsule of the knee (IPACK) block has been introduced to improve posterior knee analgesia without affecting motor function. The fascia iliaca plane block represents another commonly used regional anesthesia technique; however, comparative clinical data regarding analgesic efficacy and mobilization outcomes between these approaches remain limited.

This prospective observational study is conducted in patients undergoing unilateral total knee arthroplasty under spinal anesthesia. Participants receive either fascia iliaca plane block or a combination of adductor canal block and IPACK block as part of routine clinical practice. The study evaluates postoperative outcomes during the first 24 hours following surgery.

The primary objective is to compare total opioid consumption within the first 24 postoperative hours between the two peripheral nerve block techniques. Secondary objectives include assessment of postoperative pain intensity using the Numeric Rating Scale (NRS) at predefined time points, evaluation of early mobilization parameters, and comparison of opioid-related adverse effects.

Pain assessments are performed at 0, 2, 6, 12, and 24 hours postoperatively. Early mobilization is evaluated using standardized functional assessments, including walking ability and motor function tests of quadriceps and ankle dorsiflexor muscles. All patients receive standardized spinal anesthesia and postoperative patient-controlled analgesia to ensure comparable perioperative management.

The results of this study are expected to provide clinical evidence regarding the comparative effectiveness of commonly used peripheral nerve block techniques and to support optimization of postoperative analgesia protocols aimed at improving recovery after total knee arthroplasty.

Inclusion Criteria:

• Adult patients aged 18-80 years
• Scheduled for elective unilateral total knee arthroplasty
• Surgery performed under spinal anesthesia
• American Society of Anesthesiologists (ASA) physical status I-III
• Ability to understand the study procedures and provide informed consent

Exclusion Criteria:

• Refusal to participate
• Contraindications to spinal anesthesia or peripheral nerve block
• Known allergy to local anesthetics
• Chronic opioid use or opioid dependence
• Preexisting neurological or neuromuscular disorders affecting lower extremities
• Cognitive impairment preventing pain assessment
• Infection at the injection site
• Coagulopathy or ongoing anticoagulant therapy contraindicating regional anesthesia

The study population consists of adult patients undergoing elective unilateral total knee arthroplasty at a tertiary care hospital. Eligible participants include patients receiving spinal anesthesia and perioperative peripheral nerve block analgesia as part of routine clinical practice. The population represents individuals undergoing primary knee replacement surgery for degenerative joint disease who are suitable for early postoperative mobilization and standardized postoperative pain management protocols.

Individual participant data collected during this study will not be made publicly available. De-identified data may be shared upon reasonable request to the corresponding author, subject to institutional approval and applicable ethical and legal regulations.