Knee osteoarthritis (OA) is a progressively degenerative condition commonly associated with the aging population. It is often chronic pain that is the leading catalyst for seeking medical intervention. Radiofrequency (RF) ablation or modulation of the sensory nerve supply to the knee joint has emerged as a therapeutic option to treat chronic knee OA pain for patients who are unresponsive to conservative treatments or are unsuitable candidates for total knee arthroplasty. In the context of knee OA, RF is applied to the sensory innervation surrounding the knee, specifically the genicular nerves (GN). Due to RF novelty and the lack of standardization in procedural techniques across published studies, uncertainty remains with using RF, and currently no established treatment guidelines for knee OA recommend using RF.
To identify and synthesize the clinical data regarding the effectiveness and safety of RF modalities as an alternative therapy for knee OA.
Systematic Search Strategy
Pubmed, Medline, Embase, Cochrane Library databases were searched from inception to August 2018. All studies reporting clinical outcomes and adverse events (AEs) related to RF modalities for knee OA were included.
Used the following key word combinations: [radiofrequency ablation OR radiofrequency] AND [knee osteoarthritis OR knee denervation OR genicular nerves].
1) published RCTs, cohort studies, and case series reporting
clinical outcomes and/ or AEs with minimum 3 month
2) Patients ≥18 years of age with unilateral/bilateral knee OA contingent on radiological imaging
3) utilizing RF in one of the respective study groups as the
Methodological Assessment of Study Quality
The Detsky Scale
• Evaluated RCTs: scores of >75% (16–21), <75%– 50% (11–
15), and <50% (0–10) were considered high, medium, and low quality, respectively.
Newcastle Ottawa Scale (NOS)
• Evaluated nonrandomized studies: scores of 0–3, 4–6, and
7–9 stars represented low, medium, and high quality, respectively.
• pain scores at a minimum of three months of follow-up.
• function, patient satisfaction, quality of life (QOL), AEs at a
minimum of three months of follow-up.
• Descriptive statistics, including measures of central tendency, dispersion, and frequency were used to analyze study and patient characteristics and clinical outcomes.
Thirty-three studies, including 13 RCTs (Table 1) and 20 non-randomized studies were identified (Figure 1). Twenty four of the 33 studies were published within the last three years (Figure 2). Three studies indicated external funding source from companies that manufacture RF equipment.
Investigations were performed in Egypt (n=2), Iran (n=2), Turkey (n=10), China (n=3), India (n=3), United States (n=6), Italy (n=2), South Korea (n=1), Greece (n=1), Spain (n=2), Switzerland (n=1), and Japan (n=1).
General Study Characteristics & Quality Appraisal
• A total of 1,512 patients (mean age = 64.3 years, 32.5% males) were included. All studies were considered as moderate or high methodological quality. Thirteen, 5, and 16 studies used pulsed, cooled, and conventional (CVN) RF, respectively. Patients ranged from level I-IV on the Kellgren-Lawerence (K-L) Scale. Prognostic nerve blocks were used in 11/33 studies before RF therapy. Four and 22 studies utilized ultrasound (US) and fluoroscopy (FS), respectively.
• All 33/33 (100%) studies reported alleviation of OA-related knee pain from baseline up until 3-to-12 months with RF modalities. Six comparative studies reporting 194/296 (65.5%) and 29/150 (19.3%) of RF and control patients achieving greater than 50% pain relief, respectively.
• Twenty-eight studies reported functional outcomes, 27/28 (96%) studies obtaining enhanced functionality from baseline up until 3-to-12 months.
• Three studies reported QOL, with 3/3 studies (100%) achieving improvements in QOL from baseline up until 3-to- 12 months.
Patient Satisfaction Outcomes
• Ten reported patient satisfaction, with 8/10 studies (80%) indicating that patients were significantly satisfied. From these 8 studies, 4 were comparative studies that indicated 86/154 (56%) and 33/104 (32%) of RF and control patients were extremely satisfied or satisfied, respectively.
• Twenty-nine studies reported AEs, with 20/29 (69%) studies indicating no AEs related to the RF modalities and the remaining nine studies only indicated minor localized AEs. All 29 studies indicated no serious knee-related AEs.
Current evidence substantiates that RF modalities for knee OA potentially improves pain, functionality, and disease-specific quality of life for up to 3-to-12 months.
RF therapies yielded a favourable safety and tolerability profile, as only mild localized AEs were reported that resolved without intervention. This suggests RF modalities are perhaps an effective adjunct therapy for patients with knee OA who are unresponsive to conservative therapies.
While the majority of studies reported positive improvements on clinical outcomes, the substantial heterogeneity regarding the RF modalities, the procedural parameters of PRF and CRF, image guidance, and nerve targets, potentially limits the generalizability of RF clinical effects for knee OA.
Further RCTs with larger sample sizes and long-term follow-ups that directly compares the three primary RF modalities are warranted to confirm the clinical efficaciousness and superiority of these RF modalities for knee OA.
RF modalities for knee OA improve pain, functionality, and disease-specific QOL for up to 3-to-12 months with minimal localized complications.