Modified genicular nerve diagnostic blocks for persistent pain post total knee arthroplasty: A case report

Persistent pain following total knee arthroplasty (TKA) is a challenging condition to manage. Conceivably, persistent pain may be mediated by residual innervation to the subchondral bone. In the previous anatomical literature, targeting the middle two quadrants of the lateral and medial aspects of the distal femur was suggested to optimize capture of subchondral bone innervation. In this case report, we describe a modified injection protocol at the level of the epicondyle that provided pain relief for a patient with persistent post-TKA pain after failing to respond to genicular nerve diagnostic blocks at the classical target sites.

An 84-year-old female had right TKA in 2023 for severe osteoarthritis. The patient had right genicular nerve diagnostic blocks at the classical target sites for consideration of possible radiofrequency ablation (RFA). A 1 mL volume of contrast was injected at each location, followed by 1 mL of 0.5 % bupivacaine. The patient reported no relief from these diagnostic blocks. The patient subsequently had repeated diagnostic blocks, using a modified protocol, where two injections were performed at each of the superomedial, superolateral, and inferomedial quadrant of the knee. Following the second procedure, the patient reported 100 % pain relief for 5 hours. The patient has been scheduled for an RFA procedure.

In the current case report, a modified genicular nerve diagnostic block protocol provided pain relief for a post-TKA patient after failure of a classical injection technique. This suggests that a modified injection protocol may be necessary to select post-TKA patients for joint denervation. Future anatomical and clinical research is required.