Total knee arthroplasty (TKA) generates moderate to severe pain especially the first postsurgical days – unless the pain is managed efficiently. Multimodal analgesia (MMA) and local anaesthetics can solve the pain problem the critical first 24 postsurgical hours.

The first step of efficient pain management after TKA is MMA: Paracetamol, NSAIDs, intravenous dexamethasone, and escape opioid. The second step is local analgesics. That is mainly a choice between intraoperative local infiltration analgesia (LIA) by the surgeon or peripheral nerve blocks by the anaesthesiologist.

Complete anaesthesia of the genicular innervation would require nerve blockade of the femoral, obturator and sciatic nerves. The femoral nerve innervates the anterior knee region. The obturator and sciatic nerves innervate the posterior knee region.

Complete block of the three nerves would impede ambulation. A better strategy is analgesia of the relevant peripheral nerve branches.¹

The posterior genicular innervation is due to the popliteal plexus (the posterior branch of the obturator nerve and the tibial nerve). It can be anaesthetized either by LIA or an iPACK block or a popliteal plexus block (PPB).

The most important branch of the femoral nerve for TKA is the medial vastus nerve that innervates the medial retinaculum and the capsule. In addition, the anterior femoral cutaneous nerves and the infrapatellar saphenous nerve branch innervate the integumentum of the surgical incisional field. All these femoral nerve branches can be anaesthetized by a proximal femoral triangle block.²

The anterior inferomedial and inferolateral genicular innervation is due to tibial and peroneal nerve branches respectively. They are of occasional relevance for analgesia after TKA.

In summary, effective analgesia after TKA can be conducted by two different strategies:

(a) MMA + LIA + escape nerve blocks.

(b) MMA + nerve blocks (iPACK or PPB for the posterior innervation and proximal femoral triangle block for the anterior innervation)

References

1. Bendtsen TF et al. The optimal analgesic block for total knee arthroplasty. Reg Anesth Pain Med 2016; 41:711–719.

2. Bjørn S et al. Anesthesia of the anterior femoral cutaneous nerves for total knee arthroplasty incision: randomized volunteer trial. Reg Anesth Pain Med 2020; 45:107–116.