The extended Knee Control injury prevention program for football players showed no differences in injury incidence compared to the Adductor Strengthening Program
Compared to teams already doing some form of injury prevention, the extended injury prevention program achieved a 29% lower hamstring, knee, and ankle injury incidence
The number needed to treat is, however, high and may be not implementable in an amateur training schedule
Prevention of injury is a crucial element in many sports. Injury prevention programs are developed to reduce injury rates in various levels of sports. This study expanded an existing injury prevention program (Knee Control), which had previously shown promising results in injury prevention among young floorball players. Since there are many prevention programs available, the primary aim was to evaluate the performance of the extended version of the Knee Control injury prevention program for football players.
A two-arm randomized controlled trial was set up to compare the extended injury prevention program for football players compared to an adductor strengthening program. An additional non-randomized comparison arm was included. The two randomized arms consisted of one group performing the extended version of the previously published Knee Control program and the other group was allocated to the adductor strengthening program. The non-randomized arm comprised sports teams that already did some form of injury prevention.
During one season, adolescent or adult football players, who had at least 2 training sessions per week, received injury prevention exercises from their coaches. The coaches were invited to practical workshops to learn about the prevention program.
The extended knee control program had 6 exercises with 10 progression levels each. The table below shows the details of each program.
The third arm comprised clubs who already performed injury prevention exercises. As there was no strict recommendation to perform exercises of a specific prevention program, this was thought to simulate real training situations.
The primary outcomes were the occurrence of any physical complaint injury to either the hamstring, knee, ankle, or groin. Two questions were asked:
The secondary outcomes studied were the injury incidence rate, the weekly injury prevalence rate, and compliance with the interventions.
The study recruited 502 players between the ages of 14 and 46 years. Four-hundred and eighty-five injury events were reported in 279 players. The baseline characteristics are shown in the table below.
The primary outcomes revealed no difference in injury incidence rates for the hamstring, knee, and ankle, between the injury prevention program for football players, compared to the adductor program. Compared to the third comparison group (the non-randomized arm, already doing some form of injury prevention), the extended knee control program showed an incidence reduction of 29%. The prevalence rate was 17% and 26% lower in the players doing the extended injury prevention compared to the adductor and third groups.
No difference was seen, concerning the incidence of groin injuries. The secondary outcomes revealed compliance of 2.3, 1.7, and 1.9 sessions per week for the extended injury prevention, adductor, and non-randomized comparison groups, respectively. The time-loss injury incidence was 42% and 48% lower in the extended injury prevention program for football players compared to the adductor program and the non-randomized comparison group.
The extended version of the Knee Control injury prevention program for football players included more exercise variations. This way, participants had more options to adjust the exercise program to their capabilities.
Coaches delivered the injury prevention exercises and they received a brief training. However, it was not mentioned whether or not the coaches adapted the program. Also, it was mentioned that due to the COVID pandemic, not every coach had the opportunity to be briefed during a practical workshop. This may have caused differences in the results as we are not sure if the coaches were effectively monitoring the correct performance of the exercises. Although considering the coaches gave the exercises during training sessions, this simulated a real-life training situation, which can be valuable for amateur clubs with fewer resources.
When looking at the differences between both programs, two things catch the eye. The knee control program consists of 60 exercises (6 exercises with 10 progressions) and is compared to an adductor strength program with 1 exercise and 3 difficulty levels. Furthermore, the exercises of the knee control program can be considered to be more functional as they are performed in load-bearing positions, compared to the adductor strengthening exercises which are performed in lying positions.
Maybe surprisingly, the group performing the adductor strengthening exercises had a higher prevalence of groin injuries than both groups. Although, in this prevention study, we tend to be more interested in the incidence, which is the occurrence of new injuries during the study period. The prevalence refers to the number of people affected by the condition over a certain period. This can be interesting to look at, to determine the duration of an injury. The adductor strengthening group having the highest weakly prevalence of groin injuries is somewhat surprising as it is thought that the adductor strengthening program would at least prevent and may be more effective in treating those injuries. This could be partially explained by a change due to the COVID-19 restrictions, which mandated the use of alternative individual exercises instead of co-player-assisted exercises. These included adductor squeezes with a ball in between the knees and side-lying adduction. I hear you think indeed, these may have been too low in intensity to achieve meaningful strength adaptations.
The number needed to treat was 316 hours. According to the authors, this means that to prevent 1 injury, approximately 7 players must perform the extended knee control program during one season. This seems doable, given that the exercises can be given to the whole team during a training session. When doing the math, and assuming that one team consists of approximately 20-22 people, this program could prevent approximately 3 injuries in the team in one season.
Is this achievable? When the number needed to treat is 316 hours and we need 7 players to do it to prevent one injury among them, this equals to approximately 45h per player. If we look at the season, one season was defined as 7 months. At least 2 training sessions per week were required. If we take 4 weeks per month on average, this would give us approximately 28 weeks of training and thus, approximately 56 training sessions. Broadly speaking, 45 hours of injury prevention over 56 training sessions equals approximately somewhat more than 1 hour per training session. I don’t think a coach of an amateur football team will give his team 1h of injury prevention per training session. The upper limit of the numbers needed to treat confidence interval reveals 3620 hours of training. Using the latter number needed to treat, you can do the math yourself…
Players participating in the extended Knee Control injury prevention program for football can expect a reduction of the injury risk to the hamstrings, knee, and ankle, compared to when the players are participating in a self-selected set of injury prevention exercises. There was no difference in injury prevalence compared with the players doing the Adductor Strengthening program. The study further revealed that the Adductor Strengthening program, designed to prevent groin injuries, did not prevent them. Although, it must be noted that due to an important protocol modification, this comparison was not able to be interpreted.
Lindblom H, Sonesson S, Torvaldsson K, Waldén M, Hägglund M. Extended Knee Control programme lowers weekly hamstring, knee, and ankle injury prevalence compared with an adductor strength programme or self-selected injury prevention exercises in adolescent and adult amateur football players: a two-armed cluster-randomised trial with an additional comparison arm. Br J Sports Med. 2023 Jan;57(2):83-90. doi: 10.1136/bjsports-2022-105890. Epub 2022 Oct 31. PMID: 36316115; PMCID: PMC9872240. https://pubmed.ncbi.nlm.nih.gov/36316115/
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