Description

The International Association for the Study of Pain (IASP) has recently updated the definition of pain as "An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." This definition is complemented by explanatory notes emphasizing the subjective nature of pain and its modulation by biological, psychological, and social factors. Pain may therefore have detrimental effects on physical function as well as on social and psychological well-being.

Chronic postsurgical pain (CPSP) is defined as pain that develops after a surgical procedure and persists for at least three months following surgery. Historically, the risk of developing CPSP has been underestimated. Available data indicate that the incidence of postsurgical pain ranges from 5% to 85%, depending on the type of surgical procedure. Severe CPSP occurs in approximately 2% to 15% of patients, with reported rates of 17-21% after abdominal surgery, 6-55% after caesarean section, 5-65% after thoracotomy, 27% after hip arthroplasty, and 13-20% after knee arthroplasty. Specifically, after total knee arthroplasty (TKA), pain severity tends to plateau between three and six months postoperatively.

Knee osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage wear, leading to pain, stiffness, and joint swelling. It is highly prevalent in aging populations and is strongly associated with obesity and previous joint injury. OA affects millions of individuals worldwide, with incidence and prevalence increasing markedly with age and resulting in significant functional disability. Approximately 23% of individuals over 40 years of age are affected, with prevalence rising to nearly 80% in older populations. Major risk factors include aging, elevated body mass index (BMI), joint injury, repetitive joint overload, and genetic predisposition. Since the mid-20th century, both prevalence and incidence have doubled, largely due to increased life expectancy and rising obesity rates.

The primary therapeutic goals in the management of knee osteoarthritis are pain reduction and improvement of joint mobility. Treatment follows a stepwise approach, including exercise therapy, weight reduction, physiotherapy, analgesics, nonsteroidal anti-inflammatory drugs, intra-articular corticosteroid or hyaluronic acid injections, arthroscopic procedures, and, in advanced disease, total joint replacement followed by structured rehabilitation.

Total knee arthroplasty is considered one of the most effective surgical interventions for relieving pain and restoring function in patients with severe knee osteoarthritis. Nevertheless, residual pain and limited functional improvement remain the most frequent causes of patient dissatisfaction following TKA. Both patients and surgeons may consider the procedure unsuccessful when long-term pain relief and functional recovery are inadequate. Furthermore, older adults experiencing chronic pain after TKA may suffer from impaired social relationships and social isolation. Chronic pain in this population is also associated with depression, anxiety, sleep disturbances, and long-term opioid use, all of which negatively affect health-related quality of life.

The most relevant variables associated with the development of chronic pain following TKA can be broadly categorized into demographic and preoperative factors. Demographic factors include age and body mass index. Preoperative factors with strong supporting evidence include the severity of preoperative pain, chronic widespread pain, maladaptive health beliefs, sleep disturbances, central sensitization, anxiety, and impaired preoperative function.

Consequently, prevention of chronic pain after TKA relies on a multimodal, patient-centered approach initiated in the preoperative period. This strategy includes optimization of the patient's overall condition, active patient involvement in the surgical pathway, preemptive analgesia (such as peripheral nerve blocks and local anesthesia), optimization of surgical precision thanks to new devices (Rosa - Robotic Surgical Assistant), early initiation of physical therapy, effective management of acute postoperative pain using cryotherapy, limb elevation, and pharmacological treatment, as well as the integration of psychosocial support.

Among the various risk factors, particular attention should be given to the intensity of preoperative pain, which has been identified as a major predictor of CPSP. Strong evidence supporting this association has been reported in a systematic review published in 2024.

Preoperative pain management may be achieved through several approaches, including pharmacological therapy, physiotherapy, ketamine infusion, and locoregional anesthesia techniques such as genicular nerve blocks and adductor canal blocks. Among these modalities, radiofrequency-based interventions appear to provide the most sustained analgesic effects.

Electrical stimulation techniques have long been recognized for their analgesic properties. Among them, radiofrequency is one of the most widely used modalities in the treatment of chronic pain. Two main types of radiofrequency are currently employed: continuous and pulsed. Continuous radiofrequency (CRF) delivers continuous electrical stimulation, generating high temperatures (up to 80°C) at the target nerve or tissue, resulting in neural ablation. With increasing clinical experience, it became evident that effective pain control could also be achieved at lower temperatures. Subsequent research demonstrated that the therapeutic effect of pulsed radiofrequency (PRF) is primarily related to the electrical field generated around the target nerve rather than thermal ablation.

Genicular nerve radiofrequency ablation (GNRFA) has emerged as an innovative treatment option for symptomatic knee osteoarthritis. This technique has been shown to reduce pain and improve function, with clinical benefits often observed as early as one week after treatment. GNRFA consistently provides short-term pain relief (3 to 6 months) and, in some cases, longer-lasting benefits.

Performing GNRFA at least one week prior to TKA, as part of a comprehensive multimodal perioperative strategy, can enhance surgical outcomes by reducing preoperative pain and improving functional status, thereby placing patients in a more favorable condition to undergo surgery.