Table 3 Analysis outline for primary and secondary analysis

Descriptive statistics (sample characteristics)

Age, weight, height, side of index knee (continuous and dichotomous)

Summary statistics

1. Change in isometric knee-extensor strength Δ_t0-t1

Group 2 < Group 4

Group 4 ≈ Group 6

Change in Nm/kg (continuous)

Analysis of variance ANOVA^a

2. Change in isometric knee-extensor strength Δ_t0-t2, Δ_t0-t3

Group 2 < Group 4

Group 4 ≈ Group 6

Change in Nm/kg (continuous)

ANOVA^a

3. Change in Knee Osteoarthritis Outcome Score (KOOS) subscales Δ_t0-t1, Δ_t0-t3

Group 2 < Group 4

Group 4 > Group 6

Change in questionnaire subscales (continuous)

ANOVA^a

4. Change in Oxford Knee Score (OKS) Δ_t0-t1, Δ_t0-t3

Group 2 < Group 4

Group 4 > Group 6

Change in questionnaire (continuous)

ANOVA^a

5. Change in 6-Minute Walking Test for distance (6MWT) Δ_t0-t1, Δ_t0-t2, Δ_t0-t3

Group 2 < Group 4

Group 4 > Group 6

Change in meters walked (continuous)

ANOVA^a

6. Change in Stair Climb Test (SCT) Δ_t0-t1, Δ_t0-t2, Δ_t0-t3

Group 2 < Group 4

Group 4 > Group 6

Change in time used to ascend and descend stairs (continuous)

ANOVA^a

7. Change in current knee pain (Numeric Rank Scale, NRS) Δ_t0-t1, Δ_t0-t2, Δ_t0-t3

Group 2 < Group 4

Group 4 > Group 6

Change in NRS 0–10 (continuous)

ANOVA^a

8. Change in knee pain during the last week (Numeric Rank Scale, NRS) Δ_t0-t1, Δ_t0-t3

Group 2 < Group 4

Group 4 > Group 6

Change in NRS 0–10 (continuous)

ANOVA^a

9 Distribution in need for surgery

Group 2 < Group 4

Group 4 > Group 6

Yes, don’t know, no

Summary statistics

10. Difference in adherence to intervention between groups

Group 2 > Group 4

Group 4 > Group 6

Group 2 > Group 6

We hypothesize differences between groups in adherence (%) to the training intervention (i.e., higher number of sessions per week, the lower adherence (%))

Number of sessions, sets, repetitions and time-under-tension

ANOVA^a