The Role of Glutes in Knee Pain

The gluteal muscles have been enjoying quite a bit of attention recently in the research and are a popular topic amongst runners.

Many hope that stronger glutes will help in treating injuries and improving performance and there is at least some evidence to support this. Question marks remain however on the glutes' exact role in patellofemoral pain and the best way to address it. We'll try to shed some light on this complex area…
The gluteal muscles include Gluteus Medius, Minimus and Maximus. The main focus on this article is on Gluteus Medius which abducts and externally rotates the hip. The theory is that weakness in Gluteus Medius leads to an increase in hip adduction (the femur moving in towards the other leg) and internal rotation as demonstrated by this picture from Kibler (2006);
This increase in hip adduction and internal rotation is thought to increase the load on the patellofemoral joint and potentially lead to PFPS. We'll examine this topic in 3 main areas, muscle timing and duration, muscle strength and what you can do about it;
Glutes muscle timing and duration
Barton et al. (2013) performed a systematic review of the literature examining gluteal muscle function in patellofemoral pain syndrome (PFPS aka Runner's Knee). They found 10 studies that met their inclusion criteria, 2 of which examined glutes function during running while the remaining papers assessed other functional tasks. In all cases EMG (Electromyography) was used to compare changes in glutes activity between those with PFPS and asymptomatic controls. Barton et al. concluded,
“There is currently moderate to strong evidence that GMed [Gluteus Medius] muscle activity is delayed and of shorter duration during stair ascent and descent in individuals with PFPS. In addition, limited evidence indicates that GMed muscle activity is delayed and of shorter duration during running.”
Muscle activity that is 'delayed and of shorter duration' means that the muscle starts to work later during an activity and contracts for a shorter period. These changes are measured in thousandths of a second and may be as little as 20-30 milliseconds between those with PFPS and those without. This begs the question, how relevant are they? In a clinical situation where most clinics don't have access to EMG are we able to detect these changes? It's also worth noting that Barton et al. point out a number of methodological issues within the literature they examined and discovered inconsistent findings between the studies.
The theory is that if the gluteal muscles activate later and for a shorter period with every foot strike they provide less support to the leg and this can lead to an increase in hip adduction and greater stress on the patellofemoral joint. With thousands of foot strikes occurring during a run this difference in timing may be significant.
Glutes muscle strength
Alongside these changes in activation the strength of the gluteal muscles is thought to be important in PFPS. Prins and van def Wurff (2009) completed a systematic review of the literature on hip muscle weakness in women with PFPS. They found strong evidence of a decrease in abduction, external rotation and extension strength compared with healthy controls. This would correlate with weakness in Gluteus Medius and Maximus.
Dierks et al. (2008) examined the correlation between strength and hip adduction angle during running. They concluded;
“Runners with PFPS displayed weaker hip abductor muscles that were associated with an increase in hip adduction during running. This relationship became more pronounced at the end of the run.”
This relationship appeared to be clearer in women than men. 80% of the men in the study demonstrated a movement towards hip abduction during the stance phase (when the foot is in contact with the ground). In fact, despite their final conclusions 8 of the 20 runners in the study mirrored this finding of increased abduction.
Dierks et al. (2011) followed up their earlier work with further research that identified three distinct subgroups of running characteristics in subjects with PFPS; increased knee valgus, increased hip abduction and the more typical increased hip and knee adduction. What this highlights is the great deal of variety among individuals with PFPS which makes it very challenging to make recommendations that will help everyone. More recently Noerhen et al. (2012) examined gait changes in female runners. Their study found greater hip adduction and internal rotation in those with patellofemoral pain.
So let's recap, there might be changes in how quickly glutes activate, how long they activate for and how strong they are in people with PFPS. These findings aren't consistent across the literature and we aren't sure how relevant they are or if they cause PFPS or are created by it. Good, I'm glad I cleared that up!
What muddies the water so much with PFPS is that it is such a multifactorial problem. Research has found over 500 factors that are thought to contribute to it! What I've discussed above is really just a snippet of hundreds of articles on this topic.
We can theorise all day but really if you're a runner with PFPS it boils down to one question…
…What can you do about it?
Firstly see a Physio about it and determine if the glutes are an important factor in your pain. They will assess glutes strength and function during static and dynamic tasks. I favour the approach of Grimaldi (2011) of starting by examining simple tasks like single leg balance, looking for control of hip and pelvic alignment. Single leg squat has also been found to be a reliable tool in examining hip muscle function in those with PFPS (Crossley et al. 2011). There is some value in assessing isometric hip strength but it may only show gross weakness which is often not present in runners. Testing endurance and the ability to abduct through full range against gravity or resistance may be more useful. These tests provide information on basic glutes function but don't accurately mirror the activity of running so assessment should also include control of impact and analysis of running gait.
If glutes weakness is found there are several exercises that have been shown to improve patellofemoral pain and reduce joint loading. Dolak et al. (2011) demonstrated a 43% reduction in pain in just 4 weeks using hip strengthening exercises for PFPS. Khayambashi et al. (2012) also demonstrated improvement in strength and pain. Both studies used similar exercises including resisted hip abduction and external rotation;
In addition to these you may choose further exercises that have been shown in the research to achieve high levels of glutes activation such as sidelying hip abduction or side bridge as demonstrated in our glutes exercise video.
It's also important to encorporate weight bearing exercises to strengthen glutes in a more functional position. This might include single leg squat and single leg deadlift exercises, both of which have demonstrated high levels of gluteus medius activation in a recentsystematic review discussed here. However these exercises can aggravate PFPS so should be added gradually under the guidance of your Physio.
As symptoms settle and become less irritable a comprehensive programme designed to improve hip muscle function can be used. Wouters et al. (2012) showed improvement in hip and knee joint mechanics which could reduce load on the patellofemoral joint. They used the following exercise programme;
It should be noted though that this research used healthy subjects not those with patellofemoral pain. The exercise programme was supervised and participants recieved feedback to improve technique.
One aspects these exercises may not change though is your hip position during running. Several studies have shown improved strength without a change in hip adduction during running (as discussed expertly here by @bboyscience). The work of Wouters et al. demonstrated potential to decrease load on the patellofemoral joint but hip adduction angle and pelvic drop during running were unchanged following training.
To improve hip position during gait you may need to work directly on your running style. This is a topic in its own right so not one I'll delve into deeply here.
Closing thoughts: there appears to be a link between gluteal muscle function and patellofemoral pain, especially in women. Exercises aimed at strengthening the glutes can improve pain and function but may not change hip position during running. Patellofemoral pain is a multifactorial area so accurate assessment is important to determine what the key factors are for each individual…as ever on RunningPhysio if in doubt get checked out!
Contributed by Tom Goom, BSc, MCSP

1 comment:

  1. Thoughts about joint dysfunction (malalignment) and inhibition in muscle function?

    Or thoughts about tibial-femoral joint dysfunction being the cause of PFPS?


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