skip to main content

Femoral Block Motor Weakness — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

ModerateRegional AnaesthesiaFemoral Block Motor WeaknessFRCA Final

A 55-year-old man (ASA II) is day 1 post right total knee replacement. He has a continuous femoral nerve block catheter in situ infusing 0.125% levobupivacaine at 6 mL/hr. He reports excellent pain relief but on physiotherapy assessment he cannot straight-leg raise. Is this expected and what should be done?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Expected – quadriceps weakness occurs but reduce infusion to 4 mL/hr and reassess

Quadriceps weakness (inability to straight-leg raise) is an expected side effect of a femoral nerve block because the femoral nerve supplies the quadriceps. However, this weakness impairs mobilisation and increases fall risk post-TKR. The appropriate response is to reduce the infusion rate (to find the balance between analgesia and motor block) and supplement with multimodal non-regional analgesia. This is why many centres have transitioned from femoral nerve blocks to adductor canal blocks for TKR – preserving quadriceps power while maintaining analgesia.

Reference: RCOA – 2023 – Regional anaesthesia and acute pain module; ERAS – 2020 – Enhanced recovery for TKR