OBJECTIVES: SUMMIT, a 2-year, multicenter, randomised trial, demonstrated significant improvements in pain and function with matrix applied autologous cultured chondrocytes (MACI) implant versus microfracture in patients with symptomatic knee cartilage defects (NCT00719576). We present post-hoc results of the impact of treatment response on EQ-5D utility scores, and the overall incremental impact of treatment with MACI compared with microfracture over 2 years. METHODS: Patients (aged 18-55) with Outerbridge Grade III/IV focal cartilage defect ≥3.0cm2were randomised to receive MACI implant (n=72) or microfracture (n=72). Response to treatment was defined as ≥10-point improvement from baseline in both the Knee Injury and Osteoarthritis Outcome (KOOS) pain and function scores at year 2. EQ-5D was evaluated at baseline, and years 1 and 2. Patients’ EQ-5D responses were scored using UK-tariffs. Utility values associated with responders and non-responders were estimated based on results from both treatment arms combined. Incremental quality-adjusted life year (QALY) gains were derived by multiplying the difference in response rates between the treatments with the difference in utility between responders and non-responders. RESULTS: The mean utility score for all patients (n=142) at baseline was 0.481±0.296. Responders (n=111) had an improvement in mean utility score from baseline of 0.352 (0.833-0.481) compared with 0.033 for non-responders (n=29; 0.514-0.481) at year 2. Significantly more patients treated with MACI responded to treatment than with microfracture (87.5% vs. 68.1%, respectively; p=0.016), resulting in an incremental QALY gain of 0.11 for MACI compared with microfracture over 2 years. CONCLUSIONS: At baseline, patients with chondral defects experienced a substantially reduced HRQoL. Significantly more patients responded to treatment with MACI versus microfracture, and this response was associated with substantial improvements in HRQoL. In this population, the higher response rate for MACI resulted in an incremental QALY gain of 0.11 compared with microfracture over 2 years.