Unfortunately, every year up to 79% of recreational runners report a musculoskeletal injury, and nearly 50% of all running injuries involve the knee joint. Patellofemoral Pain is the most common knee injury in this very active population. This is potentially a large population of runners, and hopefully this blog will help some of you.
Patellofemoral pain is a common, chronic musculoskeletal condition, presenting as pain around or behind the patella during patellofemoral joint loading activities, e.g. squatting, stair ambulation and running. Patellofemoral pain has been shown to affect up to 23% of adult population, and unfortunately, this pain has been shown to persist in about 50% of cases.
Pain and symptoms associated with patellofemoral pain limit participation in daily and occupational tasks and reduce levels of physical activity. Most Importantly, Chronic or long-term patellofemoral pain may precede the onset of patellofemoral osteoarthritis.
Contributing factors of patellofemoral knee pain include:
- High Patellofemoral Joint Stress
- Overuse and Poor Exercise Programming
- Weakness of Quadriceps, calf, and/or hip external rotators
- Tight Hamstrings, Calf, Lateral quadriceps and/or ITB
Running represents a highly repetitive biomechanical pattern, with an estimation of more than one thousand steps for every 6 mins of running. Considering the repetitive nature of distance running, the accumulative Patellofemoral Joint stress over a greater distance could be related to the potential for injury.
Research has shown that altering our running technique may promote beneficial effects on lower limb biomechanics, including reduction of Patellofemoral Joint Stress. The concept; that if you reduce the stress put through the joint, this will have a positive impact on pain levels and reducing further stress to the surrounding tissue of the patellofemoral joint.
Such Techniques that have been studied to reduce patellofemoral joint stress in Running include:
- Increasing Stride Cadence
- Forefoot striking
- Forward translation of the trunk / torso
- Modification to footwear
This Blog will only cover Strike Cadence.
Cadence is the number of steps you take per minute of running, this is one of the most common metric used in running other than your min/km. Cadence is an important measurement as it can highlight how short or long your stride length may be. Cadence and stride length are important measures in not only performance but also injury management, prevention, and rehabilitation.
It is hypothesised that an increased cadence will reduce the stress through the patellofemoral joint by increasing the effort/ demand on the calf complex and foot.
In 2015, a study(1) followed the running pattern of 20 participants, both healthy and patients with patellofemoral knee pain. In this study they measured peak patellofemoral stress during foot strike, and the accumulative stress over 1km of running. The participants were asked to run at their normal (control) pace, then asked to increase the cadence by 10% and decrease cadence by 10%. The analysis of the results show that an increase in step rate (Cadence) results in 15-20% decreased peak patellofemoral joint stress per Step, and an accumulative reduction of patellofemoral stress per kilometre of 9-12% when compared to the normal/preferred running pace (control).
Interestingly a study (3) in 2018 looked at the influence of combining shoe prescription and stride length on patellofemoral joint stress. Running in control shoes at an increased cadence reduced patellofemoral joint stress by 16-19%. But when combining an increased cadence and running in a minimalist shoe; patellofemoral stress reduced on average by approximately 29% compared to the control condition.
Therefore it may be indicated that for short-term management, and rehabilitation patellofemoral knee pain, introducing an increased cadence may be beneficial.
It is important to be aware that, we are not eliminating or removing the load, but we are moving where the load/stress is being exerted. By increasing the stride cadence, the runner will be exerting more force and stress through their foot and calf complex, rather than the knee and hip.
It is not recommended that you change your running stride or technique without thorough assessment, as you may not be suited to a change in pace, stride length or foot strike due to your current strength, mobility and running biomechanics.
Although Cadence is important, it should be mentioned that there is no exact number or cadence that should be globally prescribed. There is no one size fits all, your optimal cadence depends on several factors including height, weight and running ability. Cadence, alike all other variables of running should be altered or tweaked to reflect your current goals of exercise.
Therefore, as a physiotherapist it is imperative that we manage exercise load, and biomechanical contributors with respect to patellofemoral joint stress. Running biomechanics and alterations can be expertly prescribed to assist the management of chronic and acute musculoskeletal injuries, but this requires appropriate assessment of the runner and the runner’s goals. If you are experiencing patellofemoral or any other lower limb injury, and want to continue running, it is highly recommended that you seek advice from your Physiotherapist. Here at Bend + Mend we can perform a Running Assessment to ensure your running technique is on point.
- Willson, J.D., Ratcliff, O.M., Meardon, S.A. and Willy, R.W. (2015), Running modifications affect PFJ kinetics. Scand J Med Sci Sports, 25: 736-743.
- Dos Santos, Ana & Nakagawa, Theresa & Serrão, Fábio & Ferber, Reed. (2018). Patellofemoral joint stress measured across three different running techniques. Gait & Posture.
- Bonacci J, Hall M, Fox A, Saunders N, Shipsides T, Vicenzino B. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport. 2018 Jun;21(6):574-578.