Table 2. Continuous Outcomes at Baseline and 12 Months by Treatment Groupa.
| Outcomes | Values, mean (SD) | Difference in change between groups, mean (95% CI)b | P value | |||||
|---|---|---|---|---|---|---|---|---|
| Platelet-rich plasma (n = 144) | Placebo (n = 144) | |||||||
| Baseline | 12 mo | Within-group change | Baseline | 12 mo | Within-group change | |||
| Primary outcomes | ||||||||
| Overall knee pain scorec,d | 5.7 (1.5) | 3.5 (2.6) | −2.1 (2.7) | 5.7 (1.5) | 3.9 (2.6) | −1.8 (2.5) | −0.4 (−0.9 to 0.2) | .17 |
| Annual change in medial tibial cartilage volume, %e,f | −1.4 (7.2) | −1.4 (7.2) | −1.2 (6.8) | −1.2 (6.8) | −0.2 (−1.9 to 1.5) | .81 | ||
| Secondary outcomes | ||||||||
| Knee pain while walkingc,d | 5.8 (2.1) | 3.8 (2.6) | −2.0 (2.6) | 5.7 (2.1) | 4.1 (2.8) | −1.6 (2.8) | −0.4 (−1.0 to 0.2) | .21 |
| Intermittent and Constant Osteoarthritis Pain scored,g | ||||||||
| Constant pain | 6.7 (4.1) | 3.9 (4.1) | −2.8 (4.8) | 6.7 (3.6) | 3.9 (4.4) | −2.7 (4.5) | −0.1 (−1.0 to 0.8) | .84 |
| Intermittent pain | 10.6 (4.1) | 7.4 (4.6) | −3.2 (5.3) | 10.4 (3.2) | 7.5 (5.2) | −2.9 (4.8) | −0.2 (−1.3 to 0.8) | .68 |
| Knee Injury and Osteoarthritis Outcome Scoref,h | ||||||||
| Pain | 52.9 (15.2) | 68.0 (18.2) | 15.1 (18.9) | 53.5 (13.5) | 65.4 (19.9) | 11.9 (17.6) | 3.1 (−0.8 to 6.9) | .12 |
| Other symptoms | 53.9 (15.9) | 67.2 (18.9) | 13.3 (19.0) | 53.3 (16.6) | 63.7 (20.1) | 10.4 (17.0) | 3.3 (−0.5 to 7.1) | .09 |
| Function in daily living | 58.7 (16.9) | 72.6 (18.4) | 13.9 (18.9) | 58.8 (16.3) | 71.4 (19.7) | 12.6 (17.6) | 1.3 (−2.5 to 5.2) | .49 |
| Function in sport and recreation | 30.1 (19.3) | 45.2 (25.3) | 15.1 (25.1) | 26.0 (18.7) | 40.9 (24.9) | 14.9 (21.4) | 1.9 (−3.0 to 6.9) | .44 |
| Knee-related quality of life | 33.8 (15.8) | 51.1 (20.1) | 17.2 (20.5) | 34.2 (16.8) | 48.3 (22.0) | 14.1 (19.7) | 3.0 (−1.3 to 7.3) | .17 |
| Assessment of Quality of Life–8 Dimension scoref,i | 0.72 (0.15) | 0.76 (0.16) | 0.04 (0.13) | 0.72 (0.16) | 0.76 (0.17) | 0.04 (0.12) | −0.00 (−0.03 to 0.03) | .91 |
Missing outcomes were imputed. Twenty data sets were imputed separately by group using predictive mean matching with the 5 nearest neighbors, with results combined using Rubin rules.
Adjusted for baseline value of the outcome, stratifying variables (site and Kellgren and Lawrence grade), and clustering of 2- and 12-month outcomes within participants (except annual percentage change in medial tibial cartilage volume given no 2-month data).
Measured on an 11-point numeric rating scale for average knee pain in the past week. Score range is 0 (no pain) to 10 (worst pain possible); higher scores indicate worse pain; the minimum clinically important difference (MCID) is 1.8.
A negative within-group change indicates improvement. For difference in change between groups, a negative difference favors the platelet-rich plasma group.
A single rater (blinded to group and time point) measured medial tibial cartilage volume from sagittal magnetic resonance imaging (MRI) by manually drawing disarticulation contours around the cartilage boundaries on each section using OsiriX software. These data were resampled by bilinear and cubic interpolation for the final 3-dimensional rendering. The cartilage plate volume was determined by summing the pertinent voxels within the resultant binary volume. Annual percentage change in cartilage volume was calculated as (follow-up cartilage volume − baseline cartilage volume)/(baseline cartilage volume × time between MRI scans) × 100. Because the outcome measure is annual percentage change, there are no baseline values.
A positive within-group change indicates improvement. For difference in change between groups, a positive difference favors the platelet-rich plasma group.
The Intermittent and Constant Osteoarthritis Pain score is an 11-item, 2-subscale questionnaire for knee and hip osteoarthritis, with each item scored 0 (no pain) to 4 (extreme pain). The constant pain subscale range is 0 to 20; the intermittent pain subscale range is 0 to 24; higher scores indicate worse pain; the MCID is 18.5.
The Knee Injury and Osteoarthritis Outcome Score is a knee-specific questionnaire with 42 items covering 5 subscales. Total subscale scores range from 0 to 100, with 0 indicating extreme problems and 100, no problems. The MCIDs are as follows: pain, 15.4; other symptoms, 15.1; function in daily living, 17.0; function in sport and recreation, 11.2; and knee-related quality of life, 16.5.
The Assessment of Quality of Life–8 Dimension is a 35-item questionnaire regarding health-related quality of life in the past week. The score range is −0.04 to 1.0; higher scores indicate better quality of life; the MCID is 0.06.