EP145 Chronic anterior knee pain following right total knee arthroplasty

<h3>Background and Aims</h3> Neuropathic incisional pain is a recognised complication after TKA, presenting as anterior knee pain with neuropathic descriptors such as dysaesthesia, allodynia, and hyperalgesia over the anterior patella. This case report describes a patient initially referred by orthopaedics to the pain service for a genicular nerve block post-TKA, but cutaneous neuropathic pain features were identified on the day of the procedure, leading to a modified intervention. <h3>Methods</h3> A 74-year-old retired social worker with controlled asthma and an NSAID allergy underwent right TKA on 5 July 2021 under spinal anaesthesia (2.5 mL 0.5% Marcaine), adductor canal block (30 mL 0.25% levobupivacaine), and periarticular infiltration as part of an enhanced recovery programme. Surgery involved a midline incision and medial parapatellar approach for Grade IV osteoarthritis. The patellofemoral joint was normal, ligaments were intact, and a cemented prosthesis was implanted. In November 2023, the patient developed burning anterior knee pain extending to the proximal posteromedial calf (NRS 9/10). Imaging showed no prosthetic loosening. He was referred to the chronic pain service for a genicular nerve block. However, on assessment, neuropathic features were identified, including hyperalgesia, allodynia, and dysaesthesia over the anterior patella, with reduced pinprick and vibration sensation. The procedure was modified to a medial and intermediate femoral cutaneous nerve block (figure 1, figure 2) under ultrasound guidance, with peripheral nerve stimulation confirming the diagnosis by reproducing the pain pattern. A total of 1 mL 0.25% levobupivacaine was injected per nerve. <h3>Results</h3> Post-injection, pain scores improved from NRS 10/10 to 0/10 within 24 hours, with sustained relief at one week and at day 12 follow-up. <h3>Conclusions</h3> Neuropathic incisional pain post-TKA requires targeted treatment. Options include topical agents such as capsaicin or lidocaine patches, neuromodulation (e.g., pulsed radiofrequency), or nerve denervation (e.g., radiofrequency ablation). Injectable therapies such as local anaesthetics, corticosteroids, and botulinum toxin may also be considered.