Extended knee control programme lowers weekly hamstring, knee and ankle injury prevalence

Key points

1. 01Extended Knee Control reduced combined hamstring, knee, and ankle injury incidence by 29% versus a self-selected IPEP group (IRR 0.71, 95% CI 0.52 to 0.98).
2. 02Weekly injury prevalence in those three locations was 17% lower versus the adductor group (PRR 0.83) and 26% lower versus the self-selected group (PRR 0.74).
3. 03Time-loss injury incidence was 42% lower versus the adductor group and 48% lower versus the self-selected group.
4. 04The adductor strength programme showed no reduction in groin injury incidence compared with either other group, and the adductor group had the highest groin injury prevalence.
5. 05Substantial injury prevalence was 27% and 26% lower in the extended Knee Control group versus the adductor and comparison groups respectively.

How it was conducted

Design

Two-armed cluster-randomised trial with an additional non-randomised comparison arm, covering one 7-month season (March to October/November 2020)

Participants

502 amateur football players aged 14-46 years from 46 teams in one regional district in Sweden (Ostergotland)

Groups

Extended Knee Control (n=197, 17 teams), adductor strength programme (n=125, 12 teams), self-selected IPEP comparison group (n=180, 17 teams)

Primary outcome

Injury incidence rate and weekly prevalence rate for any physical complaint injury to the hamstring, knee, or ankle combined, and to the groin

Injury capture

Weekly OSTRC-O2 questionnaires to players and coaches, supplemented by physiotherapist telephone interviews for time-loss or substantial groin, hamstring, knee, or ankle injuries

Analysis

Intention-to-treat; generalised linear models with Poisson distribution, sex-adjusted; cluster effect tested and deemed negligible

What they found

• Primary incidence (three lower-limb locations combined): extended Knee Control 7.72 per 1000 h (95% CI 6.18 to 9.66) vs adductor 9.36 (95% CI 7.01 to 12.50) vs comparison 10.89 (95% CI 8.72 to 13.59); IRR extended Knee Control vs comparison 0.71 (95% CI 0.52 to 0.98), p=0.036; IRR extended Knee Control vs adductor 0.80 (95% CI 0.55 to 1.17), p=0.246
• Primary prevalence (three lower-limb locations combined): extended Knee Control 10.87% (95% CI 9.64 to 12.25) vs adductor 13.45% (95% CI 11.67 to 15.50) vs comparison 14.76% (95% CI 13.15 to 16.57); PRR extended Knee Control vs adductor 0.83 (95% CI 0.69 to 1.00), p=0.048; PRR extended Knee Control vs comparison 0.74 (95% CI 0.63 to 0.87), p<0.001
• Time-loss injury incidence: extended Knee Control 8.12 per 1000 h vs adductor 13.64, IRR 0.58 (95% CI 0.42 to 0.81), p=0.001; vs comparison 15.77, IRR 0.52 (95% CI 0.39 to 0.69), p=0.001
• Ankle injury incidence: extended Knee Control vs adductor IRR 0.42 (95% CI 0.23 to 0.76), p=0.005; vs comparison IRR 0.53 (95% CI 0.30 to 0.92), p=0.025
• Substantial injury prevalence: extended Knee Control 12.21% vs adductor 16.41%, PRR 0.73 (95% CI 0.61 to 0.87), p<0.001; vs comparison 16.45%, PRR 0.74 (95% CI 0.64 to 0.87), p<0.001
• Groin injury incidence: no significant differences between any groups (extended Knee Control vs adductor IRR 0.58, 95% CI 0.29 to 1.18, p=0.134; vs comparison IRR 0.83, 95% CI 0.43 to 1.58, p=0.564)
• Groin injury prevalence: adductor group had higher prevalence than comparison group (PRR 2.07, 95% CI 1.39 to 3.09, p<0.001)
• Absolute rate reduction (extended Knee Control vs comparison): 3.2 injuries per 1000 hours (95% CI 0.3 to 6.1); NNT approximately seven players performing extended Knee Control for one season to prevent one injury
• All physical complaint incidence: extended Knee Control vs adductor IRR 0.73 (95% CI 0.58 to 0.93), p=0.012; vs comparison IRR 0.71 (95% CI 0.58 to 0.88), p=0.002

Limitations

• Low participation rate (18% of eligible teams) and high pandemic-related dropout mean the most motivated teams and players likely self-selected in, limiting generalisability.
• COVID-19 shortened the competitive season and required adding alternative single-player adductor exercises, complicating comparison with prior adductor programme trials.
• Self-reported injury data captured location and onset type but not specific diagnoses, limiting clinical detail.
• Small sample prevented sex-separated analyses; unequal sex distribution between groups (especially low male participation in the adductor group) required statistical adjustment rather than subgroup analysis.

Why it matters

For patients

Amateur football players who want to reduce their risk of hamstring, knee, and ankle injuries can expect meaningful benefit from regularly following a structured programme like extended Knee Control throughout the season.

For clinicians

Prescribing an extended multi-exercise Knee Control programme rather than a narrow single-muscle (adductor-only) routine produces broader lower-limb injury protection and substantially fewer time-loss and substantial injuries in amateur players.

For readers

This cluster-RCT provides moderate evidence that a comprehensive neuromuscular warm-up programme outperforms both a groin-focused programme and usual self-selected exercises for reducing lower-limb injury burden in community football.