Total knee replacement (TKR) is considered the most effective and safe method of radical treatment of late stages of knee osteoarthritis. A well-known problem of TKR is a severe postoperative pain syndrome, which is observed in more than 50% of patients.

Femoral nerve block (FNB) is the "gold standard" for continuous postoperative analgesia after total knee replacement, as it is effective in reducing the frequency of use of opioid analgetics and reduce the duration of hospitalization. At the same time, the negative effect of this method is the motor blockade of the quadriceps femoris muscle which leads to functional impairment and is associated with an increased risk of falling.

Adductor canal block (ACB) provides adequate analgesia comparable to femoral nerve block. Moreover, ACB doesn't affect the motor function of the quadriceps femoris muscle.

The possibility of enhanced recovery after total knee replacement is the reason to compare single-shot adductor canal block and continuous femoral nerve block.

Inclusion Criteria:

• Age ≥ 18
• Planned primary total knee replacement
• Planned neuraxial anesthesia
• Written informed consent

Exclusion Criteria:

• Urgent surgery
• Planned revision total knee replacement
• Known allergic reaction to anesthetics
• Confirmed localized infection at the puncture sites
• Confirmed localized tumor at the puncture sites
• Peripheral neuropathy of the lower extremities
• Parkinson's disease
• Previously enrolled in this trial