Anatomical description and short-term follow up clinical results for ultrasound-guided injection of medial collateral ligament bursa: New conservative treatment option for symptomatic degenerative medial meniscus tear.

Background: In this study, we investigated newly developed ultrasound (US)-guided medial collateral ligament (MCL) bursa injection as a conservative therapy for symptomatic degenerative medial meniscal (MM) tears. We aimed to describe the anatomical target and precise technique of this injection, confirm its accuracy using fresh cadaveric knees, and then evaluate preliminary clinical outcomes.

Methods: Anatomical studies were performed on three fresh cadavers. For the clinical study, 50 patients with medial knee joint pain without knee osteoarthritis were treated with US-guided MCL bursa injection. Severity of pain was assessed pre-injection, and 1 week and 4 weeks post-injection using a 0-10 numerical rating scale (NRS). Clinical success was defined as a full return to daily activities. All patients underwent magnetic resonance imaging (MRI) within 1 week of the first injection. Patients who underwent surgery within 12 months of the first injection were investigated as clinically unsuccessful cases, and MRI and arthroscopic findings were examined.

Results: Compared with pre-injection (6.8 ± 1.2), the average NRS score was significantly lower at 1 week (1.8 ± 2.0) and at 4 weeks (1.5 ± 1.7) post-injection (both P < 0.01). The primary clinical success rate was 76.0%, and injection-related adverse events were not observed. Nine patients underwent surgery (arthroscopic surgery for degenerative flap tear (n = 7) and high tibial osteotomy for medial meniscus posterior root tear and proximal tibial malalignment (n = 2)).

Conclusions: US-guided MCL bursa injection is safe, reproducible, and effective for symptomatic MM degenerative tears. However, US-guided injections of the MCL bursa may be ineffective for flap tears and posterior root tears.