In a study, it was found out that in middle-aged females with advanced PFCW, there is a 54% response rate at 1-year follow-up to a single or second APS injection. Moderate temporary fares are likely to occur without impacting the clinical outcomes.

This prospective, single-centre, single-arm study aimed to investigate the benefit, durability, and safety of APS injections for unilateral PFOA (patellofemoral osteoarthritis)-related knee pain. From April 2016 to May 2017, all female patients suffering predominantly from symptomatic PFOA were enrolled.

A total of 50 moderate-severe (86%) PFCW females were treated with a unilateral intra-articular APS injection. The KOOS (Knee Injury and Osteoarthritis Outcome Score), NRS (Numeric Rating Scales), Kujala, UCLA, and EQ-5D (European Quality of Life 5 Dimensions) were assessed at baseline and 1, 3, 6, and 12 months post-injection.

Based on KOOS pain improvement >10 points, TRR (Therapeutic response rate) was assessed. Absolute improvement for both therapy responders and non-responders was evaluated. The second APS injection was given if the patient demonstrated unsatisfactory improvement after 3 months.

The overall number of APS responders was found to remain stable over the study period with 53.7% at the final follow-up. After 1 year, APS responders demonstrated improvement with 30.5±11.4 points on KOOS pain. On the other hand, non-responders deteriorated with −5.9±8.9 points relative to baseline as depicted in Figure 1.

Figure 1: Absolute KOOS pain change for APS responders and non-responders. Treatment responders were defined as KOOS pain improvement >10 points relative to baseline (Mean+SD).

Overall, the enrolled subjects improved from 40.3±18.7 to 57.3±24.8 points on KOOS pain. NRS improved from 6.7±2.2 to 4.5±2.9 and the Kujala score improved from 48.4 ± 13.0 to 56.3 ± 18.1 at 12 months. The UCLA activity and the EQ-5D VAS scores illustrated no statistically significant difference at any post-injection follow-up point as shown in Table 1:

A remarkable improvement was witnessed for the other KOOS subscales at each follow-up when compared to baseline with a consistent early improvement 1-month post-injection. In 28 subjects, the second APS injection was given that illustrated low efficacy in initially poor responding patients after 3 months.

Definite synovitis patients improved more on KOOS symptoms and KOOS ADL (activities of daily living) at 12 months in comparison with non-synovitis patients. Effusion (29%) and transient arthralgia (46%) were commonly observed during the first month after injection. Thus, APS can be used as a selective treatment for advanced PFOA in middle-aged female patients.