Reduction in Synovitis Following Genicular Artery Embolization in Knee Osteoarthritis: A Prospective Ultrasound and MRI Study

Abstract

Background/objectives: Genicular artery embolization (GAE) has demonstrated potential as a treatment for knee osteoarthritis by targeting inflammation and pain, although current evidence remains limited. This study used imaging biomarkers to objectively assess synovitis and possible ischemic complications following GAE.

Methods: This was a prospective, single-center trial including participants with mild-to-moderate knee osteoarthritis. Ultrasound, contrast-enhanced (CE), and non-CE-MRI were performed two days before and one and six months after GAE. Ultrasound biomarkers included synovial hypertrophy, effusion, and Doppler activity. A combined effusion-synovitis score was assessed on non-CE-MRI, while CE-MRI allowed differentiation between synovium and effusion and was used to calculate whole-joint and local synovitis scores. The post-GAE MRIs were reviewed for ischemic complications.

Results: Seventeen participants (aged 43-71) were treated. Significant reductions were observed in ultrasound-assessed synovial hypertrophy and Doppler activity, as well as in CE-MRI local and whole-joint synovitis scores. While reductions in effusion were noted in both ultrasound and MRI, these changes did not reach statistical significance. At one month, MRI revealed three cases of nonspecific osteonecrosis-like areas, which resolved completely by six months.

Conclusions: This study demonstrated a reduction in synovitis and no permanent ischemic complication following GAE in knee osteoarthritis. Larger studies with longer follow-up are needed to confirm the long-term efficacy and safety of the procedure.

Keywords: inflammation; knee osteoarthritis; magnetic resonance imaging; trans-arterial embolization; ultrasound.

Figure 1

Ultrasound biomarkers of synovitis: (a) suprapatellar recess with severe synovial hypertrophy (arrow); (b) suprapatellar recess with major effusion (cross); (c) lateral parapatellar recess with severe Doppler activity (color) and a moderate osteophyte (arrow); (d) Baker’s cyst (arrows) with synovial hypertrophy.

Figure 2

CE-MRI at baseline and 6 months post-GAE. On axial CE-MRI, the synovial thickness of the medial (white arrow) and lateral parapatellar (grey arrow) areas, as well as a possible Baker’s cyst (dotted circle), were included in the whole-joint synovitis score along with areas scored at sagittal images. This patient, treated on the medial side of the left knee, showed a reduction in both local and whole-joint synovitis scores 6 months post-GAE (b) compared to baseline (a).

Figure 3

Ultrasound biomarkers of synovitis before and after GAE in the treated areas. Each line represents one participant. n = 17. (a,b): The ultrasound score in the parapatellar recess corresponding to the treated area was used. If both the medial and lateral sides were treated, the highest score was recorded. (c): Effusion was assessed across all three recesses.

Figure 4

MRI biomarkers of synovitis before and after GAE. Each line represents one participant. n = 17. (a) MOAKS (MRI Osteoarthritis Knee Score; [33]) from grade 0 to 3, best to worst. (b) Guermazi [20] whole-joint synovitis score from 0 to 22, best to worst. (c) The local synovitis score is a derived Guermazi score only including treated areas (parameniscal and parapatellar) and ranging from 0 to 8 (0 to 4 for participants only treated at one site of the knee), best to worst.

Figure 5

Ischemic-like lesions on MRI. Three cases of nonspecific ischemic-like lesions one month after GAE (white arrows), all completely resolved by six months. The three participants were embolized in the following areas: (a) medial side of the right knee, (b) medial and lateral side of the right knee, and (c) medial side of the left knee. In all three cases, the lesions corresponded to the treated areas.