The study results depicted that in patients with mild-to-moderate KOA (knee osteoarthritis), intra-articular HA injection is a safe and effective treatment for improving joint function and relieving pain. In the osteoarthritic knee, injection through MMP (medial midpatellar) route provides better coverage of HA to the impaired and vulnerable regions of the articular cartilage when compared to AM (anteromedial) route.

This study initially determined the intra-articular distribution of HA delivered through different injection routes in cadaver knees. Then, a prospective, single-blind, randomized, and controlled trial was conducted to investigate whether different injection routes (MMP and AM) would affect the clinical outcome of viscosupplementation in the treatment of mild-to-moderate KOA.

Overall, 42 cadaver knees with radiographic OA evidence were given AM or MMP injection of HA followed by gait stimulation. For the clinical trial, 100 patients with mild-to-moderate KOA were enrolled. All the subjects were given five weekly injections of HA through either the MMP route (N = 50) or AM route (N = 50). At the baseline visit, the patient demographics, symptom duration, K-L grade, WOMAC index, and Lequesne index were estimated.

The delivery of HA (2.5 ml) via both injection routes failed to cover the entire cartilage. With the MMP route, HA was able to cover 96.12% articular cartilage of PFJ, 71.44% of FTJ, and 52.69% of LFTJ.

However, HA covered a small part of the posterior condyle region, with only 17.75% coverage to MPC and 26.25% to the LPC. In the MMP group, the distribution of HA in PFJ was more in comparison with the AM group. However, no significant difference was witnessed in MFTJ for both groups  as depicted in Table 1: 

Mean is the mean score of the region, and N is the maximum score of the region 

PFJ; patellofemoral joint, MFTJ; medial femorotibial joint, LFTJ;  lateral femorotibial joint, MPC;  medial posterior condyle, LPC; lateral posterior condyle

The clinical efficacy was also linked with the route of drug delivery. Better improvement in pain score, WOMAC index total score, Lequesne index total score, and stiffness score was witnessed in the MMP group over the entire follow-up period, in comparison with AM group. More patients in the MMP group claimed pain relief and felt satisfying than in the AM group at the end of follow-up as depicted in Table 2: 

To treat mild-to-moderate KOA, intra-articular HA injection through the MMP route is recommended.