Biomechanical Causes of Running Injuries

For a Sports Physiotherapist being proficient at assessing running technique is as crucial as a Mechanic being able to change engine oil. Good running technique is important for both injury prevention, rehabilitation and performance. While there are common aspects, there are many more differences between endurance running, sprinting and running in field sports. For the purpose of this article I will be primarily discussing running technique in relation to field sports.

Many coaches continually make the mistake of trying to train field sports athletes the same way as a track sprinter in the pursuit of increased speed. While there definitely are a lot of training techniques that can be borrowed, essentially the goals for speed of a field sports athlete are very different to that of a track sprinter.

Basically a field sports athlete will generally only sprint a distance of about 5 to 20m, occasionally up to a maximum of 40m, and rarely any further, as well as needing to change direction numerous times. So a field sports athlete needs to accelerate a lot quicker and reach top speed a lot sooner, while changing direction, holding a ball or stick, fending and dodging other players and many other tasks. Compare this to a track athlete, where they will still be accelerating well beyond the 40m mark and sometimes even up to the 90m mark in the 100m and there is no changing direction.

I will also briefly talk about the Barefoot Running phenomenon, particularly in relation to foot strike. The barefoot running craze has recently highlighted the differences between rearfoot, midfoot and forefoot running styles and the ground breaking research by Dr Daniel Lieberman on the evolution of running has provided a lot of insight to theory behind this. Research in regards to injury prevention and performance enhancement is still lacking, however the biomechanical theory behind premise that midfoot and forefoot running styles being superior for injury prevention and performance is gaining momentum.

Swing Phase

Frontal View

• Viewing the athlete from the front or back you can see where the foot is in relation to femur when the knee is flexed. If the foot is excessively on the lateral side of the femur, the hip may be internally rotated. Conversely, if the foot is medial to the femur they may be externally rotated, and will also have to abduct the hip to ensure they don't trip over their own feet!


• Internally rotated hips are probably more common and is typically indicative of weak hip external rotators and abductors. Assessment of hip stability and strength is necessary. Secondly hip external rotation ROM should be tested, however this generally is not the cause.

Sagittal View

• During toe off look for increased anterior pelvic tilt, as seen by an increase in lumbar extension and lack of hip extension. This compensatory movement can be due to either shortened hip flexors, psoas, iliacus or rectus femoris, or a lumbopelvic instability or weakness, or more than likely a combination of the two. I assess this with a Thomas Test for hip flexor length and a variety of hip extension exercises, such as, a Bird Dog exercise with a flexed knee, looking for compensatory lumbar extension to achieve the necessary hip extension. Athletes with this movement pattern may present with a complaint of lower back pain, with pain on lumbar extension and if they don't have back pain they surely will do at some time in the future. Exercises to address this issue are hip flexor mobility drills and glute activation and strengthening exercises for hip extension.


• During the mid swing phase of the swing leg the amount of knee flexion will affect the moment arm for hip flexion around the hip joint. This is simple Biomechanics; the longer a moment arm the more force required to move it. Picture trying to pick up and Olympic bar with one hand in the middle of the bar, pretty easy right? Then picture trying to pick it up with one hand from the end of the bar, impossible I'd think. It's the same weight, but now the moment arm has dramatically increased. The same thing occurs around the hip joint and is affected by the amount knee flexion occurring at that time. The more the knee is flexed bringing the mass of the leg closer to the hip joint, the less force is required to swing the leg through. Therefore if an athlete is complaining of chronically tight and painful hip flexors assess the amount of knee flexion during swing phase and if they have decreased knee flexion they may be overloading their hip flexors to swing the leg through.


• Poor mechanics with arm swing generally doesn't contribute a lot to injury in field sports as often the arms are used to carry or manipulate a ball, stick or other apparatus or are being used to fend off an opponent or assist a team mate. However, a lot of energy can be "leaked" from the kinetic chain with poor arm swing mechanics. The arm swing should be generated from the shoulder and utilise the stretch shortening cycle of the shoulder flexors to drive the arm forwards. If the arm swing is generated from the elbow this may decrease performance, however in field sports I would think this would be low on the priority list.

Transverse View

• To view the athletes biomechanics in the transverse plane is difficult as you have to be looking down on top of the athlete. The easiest way to do this in the field is by viewing them from a high grandstand, where the athlete can run directly underneath. This is often somewhat impractical and for a field sports athlete probably a bit of an overkill. However, if you feel it is necessary to determine poor biomechanics that may be contributing to injury or poor performance, the primary component to assess is the rotation of the pelvis in relation to the shoulders. Excessive rotation of the pelvis may be due to poor core strength or stability, where the core musculature is unable to control the rotation of the pelvis. Alternatively it may be a compensatory movement caused by hip immobility, due to inadequate hip internal rotation of the extended hip, poor external rotation of the flexed hip, or a combination of both. Either way assess core stability and hip rotation to prescribe corrective exercises.

Stance

Frontal View

• Poor hip stability is best assessed by viewing the athlete from the front. The hip/pelvis on the stance leg, should have very minimal lateral movement; if the hip appears to shift laterally and the contralateral hip drops (trendelenburg), this is clinically a sign of poor hip control. Gluteus medius weakness is typically the cause, however gluteus medius weakness is also intimately related to the entire lumbo-pelvic stability system, so core stability is usually an issue as well. Therefore corrective exercises usually involve glute and core training.


• Medial knee collapse, is where the knee falls to the inside of the foot, which can come from the foot or more commonly the hip. The knee is essentially a slave to the hip and the ankle/foot. Poor hip control results in internal rotation and adduction of the hip, which causes the knee to fall inside the line of the foot. In combination to this, excessive pronation of the foot will cause the tibia to internally rotate, which will drag the knee inside the foot. So, why is medial knee collapse bad? Well, medial knee collapse, is a major cause of "patellofemoral pain", which is a general term for numerous causes of knee pain, and probably even more concerning is a movement that can potentially lead to an anterior cruciate (ACL) tear.


• Pronation/supination has been the focus of the majority of research in regards to running injuries and the main selling point of all shoe companies. Despite the fact that pronation/supination research is known to be very poor and very inconclusive; shoe companies have driven the "over pronation causes injury" line so hard in order to sell the anti-pronation/stability features of their shoes for the last 40 years that everyone just accepted it without questioning it.

That is until very recently when the explosion of Barefoot Running began and the whole idea of needing stability in a shoe was thrown out the window. As mentioned earlier Dr Lieberman has recently published research about the evolution of running, showing that prior to the evolution of the present day running shoe, humans ran predominately on their forefoot and midfoot, as opposed to heel striking, which I will discuss during the sagittal view stance leg section. Anyway, getting back to the supination/pronation topic, my view is unless their is an extremely obvious over-pronation or over supination, that can be seen by the naked eye, it is not the primary cause of the runner's pain. In reality the foot/ankle is a collection of joints that require more mobility then stability, so the idea of designing shoes to create external stability is counter-productive to this concept.

• When assessing the arm swing, ideally the arms should be moving in the sagittal plane; if the arms appear to moving excessively across the body, and not straight up and down, this could result in inefficient force transfer through the kinetic chain, and may increase the rotational torque through the core, potentially over stressing the lumbar spine. However, in field sports as the arms are generally pre-occupied with other tasks, this would very rarely be an issue.

Sagittal View

• As mentioned earlier the explosion of Barefoot Running has really questioned much of the research conducted over the last +40 years into running and shoe design. When looking at the stance leg at initial ground strike, what part of the foot strikes the ground first provides a lot of information.

The biomechanical theory to this in a nutshell is that when striking with the heel first there is a sharp spike in the ground reaction forces and the smaller muscles at the front of the shin, such as the tibialis anterior, eccentrically control the foot to the ground. This can cause a stress reaction in the tibia, "shin splints", from the initial impact and also the eccentric contraction can overload these smaller muscles and cause injury. By landing more on the forefoot and midfoot, forces are more gradually distributed to the tibia and fibula and the larger calf musculature (soleus and gastrocnemius) have a greater ability to lower the heel to the ground.

• Stride length is the other important factor to consider when viewing an athlete from the side on view. Over striding is commonly associated with heel striking and the combination of over striding and heel striking, places an enormous amount of stress on the kinetic chain. As mentioned above heel striking creates a larger ground reaction force causing bone stress injuries, but combine this with over striding and you also massively increase the stress on the hamstring. If you have an athlete with recurrent hamstring injuries, consider assessing his running technique for over striding and heel striking.

Ideally the athlete's foot should make contact with the ground just in front of the body on the forefoot or midfoot. If the foot lands way out in front of the body on the heel this can cause injury and is not an ideal running technique.

Flight

The flight phase is when both feet are off the ground and is what differentiates running from walking. The discussion of knee flexion of the swing leg above is applicable to this area as well.

Conclusion

Running is a complicated and technical task to assess and coach. My approach is to break it down into segments, such as I have done above, and try to keep it as simple as possible. Video is an excellent tool to assist with analysis and with today's technology this is quite achievable. My opinion with video is that if you need to slow it down or need high tech software to determine what the problem is your probably looking for something that isn't the cause of the problem. What I mean by this, is that if the problem doesn't stick out at normal speed it's probably not the cause. If an athlete is injured it is essential to consider what you find clinically and what the athlete tells you about the injury and combine this with the running assessment. Remember everyone has a unique running technique and you will always be able to pick out something wrong, but if the identified deficit is not consistent with the injury or complaint it probably isn't the cause. From a performance enhancement point of view, when dealing with field athletes, unless something is blatantly obvious that may be affecting performance, I wouldn't bother trying to correct it, unless I considered it a potential cause of injury, because they are not a track athlete and more than likely they will go back to their old style when on the field anyway. Track athletes are obviously a different story and any minor flaw in technique could potentially be the difference between 1st and last! If you have had a chronic running injury and your Physiotherapist has not assessed running technique, they are probably treating the symptoms and not the cause of your injury and until the cause is identified you will remain injured.