The Ultrasound-guided Anteromedial Joint Line Approach: A Targeted Corticosteroid Injection Technique for Patients With Medial Knee Pain.

BACKGROUND

Medial knee pain is a common complaint in the adult population. When conservative measures fail, intraarticular knee corticosteroid injections are often offered through the superolateral approach into the suprapatellar recess to provide short-term relief. However, some patients fail to respond and require alternative approaches. The anteromedial joint line (AMJL) approach, which targets the medial compartment, may be more effective when pain-generating pathologies such as synovitis are located in the medial compartment. To date, there have been no dedicated studies evaluating ultrasound-guided (USg) corticosteroid injections through the AMJL approach to reduce medial knee pain.

OBJECTIVES

The current study aims to assess the clinical characteristics, ultrasound findings, and clinical outcomes for patients with medial knee pain who received USg corticosteroid injections via the AMJL approach.

STUDY DESIGN

Retrospective study.

SETTING

This study took place at one academic musculoskeletal ultrasound clinic at an urban tertiary care center.

METHODS

Sixty-five patients (76 knees; 11 patients with bilateral injections) with medial knee pain who had received USg-AMJL corticosteroid injections from January 2016 through  March 2020 were reviewed for inclusion. Baseline demographic information and clinical characteristics from one year prior to 6 months following USg-AMJL injection were analyzed for each patient. Responders were defined as those who reported pain relief, decreased usage of analgesic medications, or increased physical activity. Nonresponders  were defined as those not meeting any of the responder endpoints.

RESULTS

Within one year prior to receiving a USg-AMJL injection, 51.3% (39/76 knees) had attempted superolateral knee injections without relief. Immediately following a USg-AMJL injection, 98.7% (75/76) experienced symptomatic relief. Follow-up visits took place on average at 11 weeks postinjection with 92.3% (60/65 patients) responding positively. In comparison to the responder group, the nonresponder group had a significantly older mean age (P = 0.009), lower mean body mass index (P = 0.007), and higher burden of morbidities as measured by the Charlson Comorbidity Index (P = 0.044). One patient reported a steroid flare within one week of injection. The most common diagnoses contributing to medial knee pain for these patients were osteoarthritis, medial meniscal injury, crystal arthropathy, and medial collateral ligament injury, which were supported by point-of-care ultrasound findings.

LIMITATIONS

This study was limited by its sample size and retrospective observational design.

CONCLUSIONS

USg AMJL injection is a safe and effective procedure for targeting medial knee pain, particularly in the settings of obesity and prior failed superolateral and suprapatellar knee injections. Further investigation is required to assess long-term clinical outcomes of this injection approach.