Research on hip mechanics and knee pain

Some recent research in the British Journal of Sports Medicine on hip mechanics and their effect on knee kinematics and subsequent knee pain.  Academic rigour confirms what many clinicians had suspected in cases of PFPS. Hip kinematics play a large role in knee loading in the running athlete.

The effect of real-time gait retraining on hip kinematics, pain and function in subjects with patellofemoral pain syndrome

. Division of Physical Therapy, University of Kentucky, Lexington, Kentucky, USA
. 2 University of Delaware, Newark, Delaware, USA
. Correspondence to Dr Brian Noehren, Division of Physical Therapy, University of Kentucky, Wethington Bldg rm 204D, 900 S, Limestone Road, Lexington, KY 40536-0200, USA; bwn51{at}yahoo.com
Accepted 19 January 2010
Published Online First 28 June 2010

Abstract

Background Patellofemoral pain syndrome (PFPS) is the most common overuse injury in runners. Recent research suggests that hip mechanics play a role in the development of this syndrome. Currently, there are no treatments that directly address the atypical mechanics associated with this injury.

Objective The purpose of this study was to determine whether gait retraining using real-time feedback improves hip mechanics and reduces pain in subjects with PFPS.

Methods Ten runners with PFPS participated in this study. Real-time kinematic feedback of hip adduction (HADD) during stance was provided to the subjects as they ran on a treadmill. Subjects completed a total of eight training sessions. Feedback was gradually removed over the last four sessions. Variables of interest included peak HADD, hip internal rotation (HIR), contralateral pelvic drop, as well as pain on a verbal analogue scale and the lower-extremity function index. We also assessed HADD, HIR and contralateral pelvic drop during a single leg squat. Comparisons of variables of interest were made between the initial, final and 1-month follow-up visit.

Results Following the gait retraining, there was a significant reduction in HADD and contralateral pelvic drop while running. Although not statistically significant, HIR decreased by 23% following gait retraining. The 18% reduction in HADD during a single leg squat was very close to significant. There were also significant improvements in pain and function. Subjects were able to maintain their improvements in running mechanics, pain and function at a 1-month follow-up. An unexpected benefit of the retraining was an 18% and 20% reduction in instantaneous and average vertical load rates, respectively.

Conclusions Gait retraining in individuals with PFPS resulted in a significant improvement of hip mechanics that was associated with a reduction in pain and improvements in function. These results suggest that interventions for PFPS should focus on addressing the underlying mechanics associated with this injury. The reduction in vertical load rates may be protective for the knee and reduce the risk for other running-related injuries.

Research on gait and stride rate

Some interesting research looking at the effects of muscle activation and stride rate. 
It effectively shows that an increased stride rate increases eccentric muscle 
contraction in preparation for ground loading.









Elizabeth S. Chumanov
, 
Christa M. Wille
, 
Max P. Michalski
, 
Bryan C. Heiderscheit

   Received 8 June 2011; received in revised form 28 January 2012; accepted 13 February 2012. published    
   online 19 March 2012.

Running with a step rate 5–10% greater than one's preferred can substantially reduce lower extremity joint moments and powers, and has been suggested as a possible strategy to aid in running injury management. The purpose of this study was to examine how neuromuscular activity changes with an increase in step rate during running. Forty-five injury-free, recreational runners participated in this study. Three-dimensional motion, ground reaction forces, and electromyography (EMG) of 8 muscles (rectus femoris, vastus lateralis, medial gastrocnemius, tibialis anterior, medial and lateral hamstrings, and gluteus medius and maximus) were recorded as each subject ran at their preferred speed for three different step rate conditions: preferred, +5% and +10% of preferred. Outcome measures included mean normalized EMG activity for each muscle at specific periods during the gait cycle. Muscle activities were found to predominantly increase during late swing, with no significant change in activities during the loading response. This increased muscle activity in anticipation of foot-ground contact likely alters the landing posture of the limb and the subsequent negative work performed by the joints during stance phase. Further, the increased activity observed in the gluteus maximus and medius suggests running with a greater step rate may have therapeutic benefits to those with anterior knee pain.

Keywords: Cadence, Step rate, Running

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Running and Rotation

Running Form

A post that follows on from a previous post (“Running Posture and Injuries) looking at rotation in the thoracic spine

Thoracic rotation and the low arm drive

Have you seen the distance runner with the low arm action? The runner with a decreased flexion at the elbow hanging around the waist? Is this significant with regards to efficiency? Does it impact on injury? Let’s take a look at the possible effects in the thoracic spine.

Our arms are used as a means of propelling the lower body throughout the gait cycle. The arms play an important role in balance and stability, particularly in the thoracic spine and its subsequent actions in the lumbo-pelvic region. The control of, and action can play a vital role in maintaining lower impact forces.

With a low arm drive the lever is lengthened, creating a need for larger forces to be generated. With this occurring there is an increased distance for the arm (in this case the hand being the distal part) to travel from in front of the body to terminal arm swing (behind the body).  This increased distance takes longer and requires more effort. Often that effort involves the larger muscles of the torso (trunk rotators) as a means of ‘driving’ the arms.

Fig 1. Low arm drive increase rotational forces through thoracic spine. This encourages greater force activation from the larger torso muscles.

This position not only takes longer, it also encourages a kyphotic position of the thoracic spine and increases the rotation demand through the lower thoracic and upper lumbar region. The upper thoracic spine (T1-T6) is better designed to take rotational forces and does so in a more upright (extended) position. In an extended position the facet joints create a better joint axis for rotation to occur.

With rotation coming from lower down the spine it also encourages an increased shoulder rotation travelling in an inferio-lateral direction; that is, as the left leg reaches mid to late swing, the right shoulder drives towards the left and inferiorly. This increased load on the left leg (in this case) results from the rotational drive ‘into the ground’. The opposite side must then return from this position, once again increasing the load on the thoracolumbar spine.

Fig 2. Rotation through the right shoulder will increase loading on left foot strike

Not only does this increase lower limb loading, it also increases energy expenditure for a given speed. With this occurring it would appear to increase ground contact time – the slowest portion of the gait cycle! If you want to be quicker – spend less time on the ground! Further load is appreciated when you consider the calves have to contract concentrically and eccentrically over a longer period of time in preparation for toe off.

Low arm swing may also throw energy in a lateral direction. This creates movements travelling in all sorts of directions, often ‘fighting’ against each other!

If you want to change lower limb loading, starting with a change in the upper limbs. This can be achieved in a two-step process;

1.    Increase the elbow flexion to between 90-110- deg

2.    Extend the upper thoracic spine to allow rotation to occur in the upper thoracic spine

This often aids in a quicker arm swing over a shorter distance and decreases rotation from the thoracolumbar spine.

Rotation in the extended position acts more like a ‘spring’ increasing the efficiency of the posterior chain (thoracolumbar, lats and glutes on the opposite side). Efficiently utilising this system also increases force closure of the SIJ – another stabilisation mechanism during running. 

This is not a ‘one size fits all’ approach, but a position from which to start with rotational forces that are a strong contributing factor to loading and/or injury.

Running Posture

Running posture and injury

Clinical Observations

A longer post today that may ask more questions than it answers! Hopefully it will be engaging and encourage the interested reader to explore the practical applications from our discussion.

Running is a skill that must be learned, to perform efficiently. Although we are not taught to run from an early age, the fundamentals are probably hard wired into the brain from about 18 months, when toddlers decide to move around faster. As with many movements they are refined in the early years of development and certain habits and postures are picked up and retained for a variety of reasons.

The human nervous system learns required motor patterns and uses those in the most efficient way possible (this is not to say it is the most efficient way), it’s almost the path of least resistance. In fact it may be down right dysfunctional! For this reason, it is hard to unlearn a motor pattern. In fact, experts who study pain involvement and the nervous system would tell us that you cannot ‘unlearn’ a motor pattern, but you can learn a new motor pattern in preference to an old one. For this very reason ‘poor patterns die hard!’

While the fundamentals of running biomechanics are there for most, if and when we decide to start running as a means of exercise we often carry these patterns over. With continual training we then drive them home as we constantly pound the pavement in an effort to get fitter and faster. Dysfunctional patterns are re enforced with every step.

Before we look at the running posture it’s important to understand we are talking about distance running and not sprint running – the two have vastly different running mechanics.

The major influences;

Posterior pelvic tilt

A posterior pelvic tilt is a common problem. It becomes more pronounced and noticeable as we become sedentary and seated in our day jobs. Poor pelvic position seated may carry over to our athletic and running endeavours.

While there are differences in pelvic angle regarding ethnicity ie; Afro-americans have a more anterior pelvic tilt and Asian countries tend to be slightly more posterior, most of us tend to fall into this position. We then adopt this new position rather than retaining our anterior to neutral pelvic angle developed during our growth and developmental years.

A posterior pelvic tilt tends to reduce boney and myofascial stability around the lumbar spine causing load through the intervertebral disks. This position also ‘locks’ the SIJ, encouraging a hitch through the swing phase during gait. Further to this, lack of extension in the hip is observed. Lack of extension through the toe off inhibits full activation of hamstrings and glutes. The trade off being facilitated quads and hip flexors further compounding the problem. This often reduces firing of the gluteus medius especially the posterior portion being placed on such length in the eccentric position during midstance.

Fig 1. Posterior pelvic tilt causing a myriad of problems


The last big notable problem arising from posterior rotation of the pelvis is over striding. Over striding places increased loading on the anterior structures as they eccentrically load through increased ground contact time. This increased contact time forces the calves to work over a longer period of time, often these are the runners that complain of ongoing calf injuries. This is also a culprit in rear foot loading and ground collision - an area of hot debate at the moment with the popularity of bare foot running (a topic in itself)

Kyphotic thoracic spine

A kyphotic or ‘rounded shoulder’ position may be adopted over time or may be due to a particular disease process (osteoporosis, scheumanns disease) or a predisposition. We will focus on the adopted form.

Lack of extension tends to occur as we leave our developmental years and assume more sedentary postures. It does not occur over night. With rounded shoulders, flexion through the mid to upper thoracic spine occurs ‘opening up’ our facet joints and causing us to become stiff and less mobile.

With flexion in the thoracic spine comes a loss of rotation. Rotation in the thoracic spine is extremely important in the counter movement of the opposite hip/SIJ. As the left hip drives forward from mid to terminal swing phase, the right shoulder and thoracic also rotate to the left, causing a counter rotation. This also assists in preparing the myofascial system to ‘wind up’ and store energy through the right latissimus dorsi and left glute max. Activation of these structures causes closure of the SIJ giving stability to the pelvis. A lack of mobility can therefore cause instability to the SIJ setting up a myriad of problems

Anterior displacement of the pelvis

An anterior displacement of the pelvis typically occurs in those hyper mobile persons or those standing for long periods of time. If this position is adopted during running posture a variety of problems can occur.

If coupled with an anteriorly rotated pelvis there will be impingement in the lumbar spine loading the disks at L4/5 and possibly referring posteriorly down the thighs. Conversely when coupled with a posterior rotation (more common) the hip flexors become so overactive eccentrically trying to control the forward position of the pelvis, the glutes go into hibernation. This causes similar problems to a posterior rotation alone though to a higher degree.

Pelvic stability is often a key factor for this type of runner (posturally speaking)  - usually there is joint laxity about the hip/SIJ and stiffening up of the joint(s) and placing them in a better position often improves dysfunction about this area.

With poor joint stability, increased loading and forces will be taken up by boney and joint surfaces as opposed to connective tissue, which are better designed to withstand compressive and tensile loads. Soft tissues also repair to some degree where as joint surfaces do not!

Anterior pelvic rotation

This scenario is a problem far less frequently from a clinical perspective unless it is a big rotation. This tends to load up the lower lumbar spine causing stiffness and possible impingement. This is also the runner that tends to land in a more pronounced forefoot position, giving the calves and achilles a lot to think about!

The bigger concern is a compensatory kyphosis of the thoracic spine (discussed earlier).

Unilateral rotations of the ilia (including inflare and outflare)

These do present in the clinic and can be either from long term occupational overuse or from an acute episode ie; lifting. Usually they are easy to assess and gain control over. The side that rotates away from the ‘normal’ for that person will usually be the symptomatic side.

BUT, if the rotation is not attended to early, compensatory patterns can set in making the treatment process a little more complicated.

Final Thoughts

It always amazes me that most sports even at a club level will consider form and biomechanics as an important of the development of an athlete yet running is an assumed skill. Running is a skill and similar to all skills it must be developed. Runners at national level do not practice form - it is a case of physiology and ‘just going harder’ unfortunately, this does not always work.

The question might be, are these runners at this level because they are more economical and efficient and adopted good patterns early on, or did they develop this as a way to get faster, fitter etc?

Treatment for the running athlete will be addressed in a future post. Until then…..

Happy Running!

Jimmy

I am happy to discuss further if anyone would like to contact me

Jimmybarker9@gmail.com

Sesamoiditis

Sesamoiditis

A complaint by distance runners or running based sports seen less commonly in the clinical environment is medial forefoot pain on the metatarsal head otherwise known as sesamoiditis. This is generally acutely painful with a short build up bought on by increases in load through the forefoot, typically volume, intensity and sprint type work including hill sprints.

The sesamoid bones are actually two small bones embedded within the tendon of the flexor hallicus longus (tendon that inserts underneath the great toe). The function is to increase the mechanical advantage during great toe extension acting as a fulcrum.

Under normal circumstances the forefoot spreads the load over the foot including the plantar fascia and also absorbs load through the fat pad covering the ‘ball of the foot’. There are several reasons this injury may present such as;

·      Increase in volume

·      Increase in intensity

·      Increase in hill sprints (forefoot load)

·      Increased pronation

·      Valgus great toe

·      Decreased great toe extension

·      Decreased dorsiflexion

·      Pelvic instability – causing changes in the foot strike

Fig 1. Location of the two sesamoid bones, overuse can cause friction between the tendon bone interface or between the bones themselves.

Treatment

Addressing the factors that promote dysfunction or increase the load on this area is paramount. As usual addressing the symptom alone is a poor choice of treatment, hence outcome.

Soft tissue therapy to areas of focal thickening in the calf and joint mobilization addressing portions of stiffness in the ankle and first MTP (metatarsophalangeal joint) are often helpful.

Pelvic positioning and firing of pelvic stabilisers often addresses foot position decreasing load on the area Runners who overstride and attempt to land on the mid to forefoot (as is all the rage at the moment) are at risk of increased eccentric load over a longer period with increased ground contact times.

Anti-inflammatories may be helpful in the short term after the initial acute inflammatory process has calmed down. A period of 3-5 days often provides a benefit where further treatment can progress. It is contraindicated to treat a joint or an area that is acutely inflamed. A small donut shaped foam padding may decrease pressure on the forefoot allowing the joint to settle down.

Taping the great toe out of valgus and applying soft tissue treatment to flexor hallucis brevis and abductor hallucis (these are small intrinsic muscles in the mid to forefoot) often allows the joint to improve mobility and helps to re-educate the toe position.

Fig 2. A valgus toe angle may represent changes in hip stability further up the kinetic chain. This places undue strain on the medial joint capsule and further loads the sesamoids.

Modifying the training load including speed work and hill efforts should be a consideration with a gradual build up on return.

Prognosis

If caught early and with the appropriate treatment a successful outcome is often the case. In recalcitrant cases and after 6 months of conservative treatment further investigation may be warranted.

Jimmy

Achilles and eccentric loading

Achilles Tendinopathy: Are heel drops for me?

A common question in the clinical environment is “when should I start heel drops (eccentric loading) for my Achilles?”

Before we answer that question we should consider if they are appropriate as a part of a rehabilitation program. Not all cases of Achilles Tendinopathy will respond in a positive manner.

Let’s take a brief look at your options at different stages of pathology:

Acute stage – in the case of an acute bout of Achilles pain in the distance runner we still do not really know if/how much the inflammatory response is involved in this type of scenario. Despite showing signs and symptoms it is not conclusive. The fact that tendinopathies tend to operate on a continuum may suggest multiple occurrences.

In any case a period of tendon de-loading is recommended. This allows the tendon to go through the initial healing process. There are two presentations here in the acute onset;

1.     An acute overload leading to a (possible) inflammatory exudate within the paratendon (tendon outer layer/covering)

2.     An acute onset with a degenerative pathology being the underlying condition. In this case the pathogenesis has probably been going on behind the scenes without any symptoms. The onset will be acute, the pathogenesis not so.

Chronic stage(s)

1.     Chronic Achilles Tendinopathy is common in cyclic sports such as running and as such presents with a long history of nagging pain progressively getting worse as the runner continues to load the tendon. As stated tendon pathologies occur on a continuum with a progressive overlapping of stages., chronic may be considered to be the end stage

How do we know the difference?

This can be difficult however, usually acute signs will be due to high loads over the short term (days/weeks) and will be exquisitely tender to run and/or palpate.  It may also be red, hot and swollen and may present with crepitus. This can sometimes be heard as the tendon glides within the paratendon, almost like a ‘creaking’ sound.

An acute onset with an underlying degenerative process does not (usually) present with this scenario. Typical signs here are a thickened Achilles tendon, stiffness and pain on awakening only to warm up. There may be thickened nodules palpable typically through the mid-portion. Often there is accompanying lack of range in dorsiflexion.

Further investigation such as MR imaging or ultrasound may show further degenerative changes and is our most reliable form of assessment.

Chronic Achilles Tendinopathy as the name suggests has presented itself months before and despite a low level of nagging pain and stiffness the runner continues to log the miles. Chronic cases almost always show multiple changes at the cellular level (these have been discussed in a previous post – “The old Achilles”)

What else needs to be considered?

The second factor, which is huge in Achilles pathology, is location. Achilles pain presenting in the mid-substance (2-6cm above insertion) generally has a better prognosis than pain at the insertion (less than 1 cm above insertion). The reasons are not clear, further research is needed to fully understand the complex nature of insertional tendinopathies.

Heel drops may be appropriate for chronic Achilles patients where the mid portion is involved. Insertional tendinopathies generally show poor outcomes with heel drops as the aetiology is thought to be different (compression is believed to be a large factor involved with insertional tendinopathies). Dropping the heel below parallel as with eccentric loading places increased compression on the tendon. Insertions generally do not like to be stretched. Taking the load off the tendon with heel inserts often proves beneficial.

Clinical experience will show those that embark on heel drops with insertional pathologies will generally have a poor outcome. A better place to start may be heel drops from the floor – this reduces the compressive factor but still applies a progressive load.

Acute tendinopathies do not tend to respond in the same way clinically. Loading tissues showing hallmarks of inflammation (acute only) tends to further irritate the tissues. A period of de-loading for 1-2 weeks is recommended before a decision on heel drops is made. Subjective and objective history will be your guide here.

How Long can I expect to see results?

There is no consensus on a ‘standard’ for loading parameters however the original research provided by Alfredson (1998) is often used as a starting point. He used 3 sets of 15 reps straight leg and bent leg heel drops performing only the eccentric portion on the affected leg over a 4 second descent. These were performed twice daily, through moderate pain with the weight progressively increasing. A total of 180 reps is performed daily over a 12-week period. Improvements need to be monitored weekly and progression made accordingly

Summary

Heel drops are indicated in most chronic mid portion Achilles tendinopathies. Acute and insertional tendinopathies require modification and management. As tendon research improves so will our understanding of clinical treatment. This is one aspect of conservative therapy and thus needs to be determined if it is appropriate.

For further information on tendon research Professor Jill Cook, Dr Jamie Gaida and Craig Purdam (AIS) from Australia are at the forefront. Overseas pioneers in this field include Hakan Alfredson and Lars Ohberg. An abundance of information can be found in journals and on the internet for the like minded reader.