Factors That Contribute to Pathokinematics - Part II

Last week, we started to look at the factors that contribute to the pathokinematics we see in our athletes.  This week we will continue that discussion by looking at peak skeletal height. 

Peak Height:

Peak height for girls is reached between 10.5 and 13 years of age.  Males reach their peak height between 12.5 to 15 years of age[i].  Any time there is a rapid growth rate, in boys or girls, there can also be a sense of clumsiness that accompanies that growth spurt.  This is often associated with muscles being stretched.  Changes in bone length results in the muscle being placed under tension which results in altered input to both the muscle spindles as well as the golgi tendon organ.   It is the combined input of these two proprioceptors that aid in our ability to sense changes in joint angle, muscle length and tension.  Integration of these “senses” in the higher centers allows us to know the position of our joints in space.  Over time, both systems acclimate to the increase in length and balance improves. 

The timing of growth spurts and differences in the rate of growth for boys and girls can also result in muscle flexibility and strength differences between males and females.  This is particularly true for those muscles associated with the long bones, such as the quadriceps and hamstrings.  Because of these differences, we may expect to see a corresponding difference in abnormal movement patterns and associated injury rates in young males and females. 

To further explore this idea, let’s consider the differences in quadriceps and hamstrings strength in males and females.  According to a study published in the American Journal of Sports Medicine in 2006, there is a significant gender difference in quadricep and hamstring strength. [ii]   In this study, untrained individuals were studied in order to account for gender and age related changes in males and females between the ages of 9 and 17.  As age increased, there was a corresponding increase in strength in males, especially in the quadriceps and hamstrings, but increases were less in females.  Although quadriceps strength continues to increase   Because of this relative weakness in the large muscles of the lower extremity in females we might expect to see a corresponding increase in pathokinematics in sporting or other activities that involve heavy loads, high intensities, significant endurance requirements, rapid speed or directional changes, or cutting, jumping and stopping maneuvers.
for both males and females throughout this growth period, in females quadriceps and hamstring strength peaks at a much earlier age than for males, in relation to bone length.

It should also be noted that with an increase in height during growth phases there is also a change in the center of gravity, which with the previously mentioned changes in proprioception, can result in a significant change in overall sense of balance.  These factors, either alone or in combination, may suggest that females, especially young females in this age bracket may be more susceptible to lower extremity pathokinematics that ultimately lead to injury. 

Body Composition:

Active adult women have 8-10% more body fat than men of the same activity level and age.  When looking at the ratio of lean body mass to fat, it is 5:1 (5 pounds of lean mass to 1 pound of fat) prior to puberty for females.  The ratio of lean body mass to fat then changes in females from 5:1 to 3:1 between the time puberty begins and the beginning of menstruation[iii].  This means that the percentage of total body fat relative to lean body mass is greater after the onset of menstruation in females.  It is also worth noting that females have a resting metabolic rate that is 5-10% lower than in males which may also be a contributing factor to a higher percentage of body fat in general.  This is important in the discussion of pathokinematics in females because as a result of smaller amounts of lean body mass in the female body relative to fat, we may expect to see a negative impact on movement patterns, which can lead to a wide variety of lower extremity injuries over time from the lumbar spine to the foot.  This can become even more of a factor in situations where the body is subjected to higher speed, strength/power, agility or endurance requirements.

Muscle Tissue:

Muscle fiber and the total muscle cross sectional area in women averages between 60-85% as compared to the same areas in men.  As mentioned above, researchers showed in a 2006 study that there are notable gender differences in strength of quadriceps and hamstrings in trained and untrained subjects.[iv]  Ahmad, et al in 2006 also showed that female’s quadriceps strength develops at a faster rate than their hamstring strength which leads to altered quadriceps to hamstring ratios and could make them more susceptible to ACL injuries. [v]  The result is decreased dynamic control and increased stress to the ACL and knee during athletic activities in females. 

However, differences in absolute strength between sexes can virtually be eliminated when strength is expressed relative to fat free weight.  Therefore the difference in muscle strength between trained women and trained men appears to be explained solely by muscle mass or size.  When looking at fast and slow twitch muscle fibers, the proportion of fast and slow twitch fibers is nearly equal in men and women.  Considering this, women can have the same relative strength (maximum force exerted in relation to body weight or muscle size) and power gains as male athletes when strength and power is expressed relative to fat free weight.  The training implications here are that females should be involved in strength resistance training in order to increase dynamic control and thereby reduce pathokinematics that can lead to injury. 

Next week we will continue this discussion by looking at the impact that cardiovascular system has.  We hope you enjoy and share the passion and our blog with your colleagues is the biggest compliment. #ACL #Prevention @PhysioCorp

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

---

[i] Lewis DA, Kamon E, Hodgson JL. Physiological differences between genders.  Implications for sports conditioning.  Sports Med. 1986 Sep-Oct ;3(5):357-69

 

[ii] Westin,S; Noyes, F; Galloway, M.  “Jump-land characteristics and muscle strength development in your athletes: A gender comparison of 1140 athletes 9 to 17 years of age”.  Am j sports med.  34:375-384, 2006.

[iii] Jackson AS, Pollock ML.  Practical assessment of body composition. Physician Sportsmed 13: 85–86, 1988

 

[iv] Westin,S; Noyes, F; Galloway, M.  “Jump-land characteristics and muscle strength development in your athletes: A gender comparison of 1140 athletes 9 to 17 years of age”.  Am j sports med.  34:375-384, 2006.

 

[v] Ahmad, C.; Clark, M.; Heilman, N.; Schoeb, S.; Gardner, T; Levine, W.  “Effect of Gender and Maturity on Quadriceps to Hamstring Ratio and Anterior Cruciate Ligament Laxity”.  Am J Sports Med. 34:370-374, 2006.

Factors That Contribute to Pathokinematics

During this most recent series we have looked at the impact pathokinematics has on injury risk and performance.  After hearing this, the question arises, what is it that sets an athlete up for pathokinematics in the first place?  Is it genetic, is it a learned response, or is it weakness or poor conditioning?  Is it related to gender?  In reality it may be a combination of all of these factors.  We do tend to see certain kinds of lower extremity pathokinematics more frequently in females than in males[i] (Huston, et al. Am J Knee Surg. 01).  Research suggests as mentioned previously, that females are more prone to certain kinds of lower extremity injuries as a result, including for example, ACL tears.  Why might this be so? 

We all know that females and males have inherent physiological and anatomical differences.  In the following paragraphs, we will take a look at several of these differences that we know contribute to a greater number and more frequent occurrence of certain pathokinematic movement patterns in females, and consequently a greater number of certain kinds of lower extremity injuries.  Let’s begin by looking at the most obvious group of differences between males and females, namely those related to body structure and posture.  These include obvious differences in skeletal make-up, peak height, body composition, muscle tissue, and the not so obvious circulatory and cardiorespiratory capacity differences[ii].  We will also review other differences in males and females that may serve to further explain the increased frequency and types of pathokinematics we see in women including those related to biomechanics, neuromuscular function, kinesthetia or proprioception, hormones, and core (including the hip) strength.

Structure / Skeletal Make-up:

From anatomy we know that the female pelvis is wider than that in males.  This increased width facilitates pregnancy and childbirth.  However, the wider pelvis in females alters the position of the femur and adds to increased Q-angles at the knee where the tibia and femur articulate.  The Q-angle, or quadriceps angle, is formed in the frontal plane by two line segments:  one that is drawn from the tibial tubercle of the middle of the patella, and another drawn from the middle of the patella to the ASIS, or the anterior superior iliac spine.  The Q-angle in normal males as determined in a study of 75 males and females was 14 degrees (+/- 3) for males and 17 degrees (+/- 3) in females.[iii]   While it has been speculated that the female Q-angle can contribute to ACL loading by positioning the knee in valgus (knock knee position) and thereby place additional stress on the ACL in this population, this supposition has not been supported by any experimental data as of this writing.[iv]

We also know that females have a smaller femoral notch than males when we look at male and female anatomy in comparison[v].   In looking at female pathokinematics and the likelihood of ACL injury, we can see why this might be an important structural difference between the two sexes.  The ACL originates at the posterior portion of the intercondylar notch of the femur.  It is speculated that a decreased notch space can lead to increased stress or wearing on structures of the knee, namely the ACL, most notably during twisting and cutting motions.  It is thought that a decreased notch space coupled with excessive hip or knee rotation could result in excessive loading of the ligament and thereby increase the wear and tear of the ligament and possibility of rupture.

These anatomical differences in pelvic anatomy between males and females may also contribute to increased weakness of the gluteus medius, lower abdominals and the transverse abdominus in females.  All of these can contribute to less neuromuscular control of the core and hip which is so critical for controlling motion in the lower extremity.  We will discuss this in more detail in later sections of this chapter. 

Finally, females tend to achieve peak bone density at approximately 28.3 to 29.5 years of age (Recker, et al, JAMA 92)[vi].  Over time and with age, both male and female bones naturally deteriorate.  There are factors that positively influence this like calcium supplementation as well as resistance exercise.  Studies indicate that there is a biopositive adaptation process that occurs in the bones with resistance exercise and with sports (Krahl, et al. AJSM 94)[vii] and this adaptation can lead to higher peak bone densities than would occur without exercise.  However there is a gender difference with female bone loss occurring at an accelerated rate in comparison to males.  This tends to occur during the ages of 45-55 years of age and can lead to an increased risk and likelihood of fracture with increasing age.  Additionally, females are much more likely to suffer from osteoporosis (disease in which bones become more porous due to a reduction in bone mineral density).  In some instances, this reduction in bone mineral density is exacerbated by the effects of estrogen deficiency that occurs following menopause, as well as several other factors common to females.  Fractures in situations such as falls that would not have occurred in healthy adults with normal bone density are the primary risk in individuals with osteoporosis.  Full weight bearing exercise as well as strength training are effective preventative strategies to manage and even reverse bone loss associated with osteoporosis.  Consequently, females benefit greatly from incorporating weight bearing and strength training exercises into their training programs early in life to aid in development and maintain more optimal bone density later in life. 

Next week we will continue to investigate the impact skeletal maturity has on pathokinematics.  Stay tuned and share the passion. #ACL #Prevention @PhysioCorp

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

---

[i] Huston LJ, Vibert B, Ashton-Miller JA, et al. Gender differences in knee angle when landing from a drop-jump. Am J Knee Surg. 2001;14:215–219.

 

 

[ii] Arciero,PJ. Goran, M, Poehlman, A.  Resting metabolic rate is lower in women than in men. J. Appl. Physiol. 75(6): 2514-2520, 1993.

 

[iii] Agliettis et. al. Clin. Ortho 1983.

 

[iv] Pantano, K. J., White, S. C., Gilchrist, L. A., and Leddy, J.: Differences in peak knee valgus angles between individuals with high and low Q-angles during a single limb squat. Clinical Biomechanics. In Press, Corrected Proof.

 

[v] Shelbourne, D; Davis, T; Klootwyk, T. The Relationship Between Intercondylar Notch Width of the Femur and the Incidence of Anterior Cruciate Ligament Tears: A Prospective Study Am J Sports Med May 1998 26 402-408

 

[vi] Recker RR, Davies KM, Hinders SM, et al: Bone gain in young adult women. JAMA 268:2403 –2408,1992

[vii] Krahl, H; Michealis, U; Pieper, H; Quack, G; Montag, M. Stimulation of Bone Growth Through Sports: A Radiologic Investigation of the Upper Extremities in Professional Tennis Players Am J Sports Med December 1994 22 751-757

 

Athletes and Pathokinematics - Part V - Lumbar Spine

Pathokinematics can have as profound an impact at the sacral and lumbar spine as they do at the hip, knee, foot and ankle.  As described previously, we typically see pathokinematics result in one or a combination of the following movements at the pelvis/lower lumbar spine

1.     Trendelenburg (dropping of the pelvis on the contralateral side during weight bearing on the ipsilateral side)

2.     Lumbar sidebending

As you can see on the diagram, the pelvis, sacrum and lumbar spine are intimately involved with one another.  Motion in one will result in motion of the structure superior and inferior to that structure.  Therefore, if the pathokinematics listed above occur in high loading situations or during high impact sports, it can alter the angles of the articulating surfaces which, in turn, can drastically alter the length tension relationships of the musculature supporting the sacral and lumbar spine.  Also, this can result in abnormal force attenuation on the bones, tissues and ligaments of the sacral and lumbar spine, all of which can lead to several problems including:

1.     Sacroiliac (SI) joint pain – the sacroiliac joint, is the joint between the sacrum and the ilium of the pelvis.  By its architecture, it is designed to withstand compression and some components of shear force.  However, it does not do as well with larger magnitude shearing stresses, especially when they are repetitive in nature or when they are combined with high impact sports.  This joint has a very small amount of movement and the exact degree is still debated in the literature at this time.[i]   Some authors report this movement to be as little as 2 degrees and some claim it is as high as 18 degrees.  Whatever the actual degree of movement is, excessive movement of this joint can result in pain and dysfunction.  With a trendelenburg movement pattern, shear stresses to the SI joint (in particular the articulating surfaces) are increased and this in turn increases shearing loads to the supporting ligamentous structures (anterior and posterior sacroiliac ligaments).  Ultimately, this can result in pain as well as increased laxity in the joint.  This increased joint laxity can result in an increased likelihood of movement in the joint when sustaining greater loads and single leg activities. 

2.     Facet syndrome – on the posterior aspect of the lumbar spine are the facet joints, with one on   Each vertebral body has both a superior and inferior articulating process.  In the diagram to the right, the inferior articulating process of L4 articulates with the superior articulating process of L5.  These joints are compressed together during extension of the lumbar spine and gapped during flexion of the lumbar spine.  The facets on the right are compressed with right side bending and gapped with left side bending and vice versa.  When a trendelenburg is present in high loading situations, this results in gapping of the facets on the side on which the hip is falling and compression of the facets on the side on which the hip is elevated.  This excessive movement can result in:

the right of the spinous process and one on the left of the spinous process.

a.     Osteophyte formation –  this is a bony formation along the facet joint that can result in narrowing of the neural foramen.  This can result in pain in the joint as well as impingement of the nerve root.

b.     Inflammation of the joint – this inflammation can result in pain with extension or side bending activities as well as inhibition of related musculature (specifically the multifidus).

c.     Early Degenerative Joint Disease – both osteophyte formation and inflammation can result in early deterioration of the joint resulting in decreased mobility of the lower lumbar spine and pain.

3.     Disc pathology – the intervertebral disc is composed of the annulus fibrosus (outer layer) and the  It is located between the vertebral bodies from the cervical spine to the lumbar spine.  Its function is to resist compressive forces imparted to the spine and it is the shock absorber of the spine.  Shearing forces imparted to this structure (via trendelenburg and sidebending of the lumbar spine) can result in degenerative changes within the disc.  Over time, this can result in:

nucleus pulposus (the inner layer).

a.     Disc bulge – a disc bulge results when the nucleus migrates to one side (right or left) and results in annulus fibers bulging out on one side.  This bulging will often result on the side in which the more frequent side bending occurs or on which the magnitude of the force is higher.  This can result in pain or impingement of the nerve root.

b.     Disc herniation – a disc herniation is a progression of the disc bulge.  A herniation occurs when the nucleus actually migrates out of the annulus.  Mechanisms of injury are similar to those above however this is a much more involved injury.  With herniation, there is a significant inflammatory response and pain, and it is often associated with radicular symptoms (pain, numbness or weakness down the leg).  Depending on the severity, this can require surgery to repair.

c.     Disc narrowing – with repetitive wearing of the tissue and its resulting breakdown, we can see a narrowing of the intervertebral space.  Over time, this can result in early fusion of some of the lower lumbar segments (most commonly L5/S1), and a resulting decrease in mobility of the lower lumbar spine and/or pain. 

4.     Muscle strains – There is a tremendous amount of musculature (superficial and deep) of the   Imbalances in this system can lead to decreased motion of the spine, abnormal motion of the spine and pain.  With pathokinematics, a lot of musculature of the lower lumbar spine is compromised.  This is due to several factors:
lumbar spine.

a.     Change in length tension relationships – with so many of the muscles of the lumbar spine having attachments to the pelvis and spine, side bending or a trendelenburg significantly changes the length tension relationships of these muscles and thereby dramatically alters their maximal force they are able to produce.  This also results in altered force production between the right and left sides of the lumbar spine.  These in isolation or combined can result in muscles being weakened and therefore unable to resist the load imparted to them, resulting in muscle strains. 

b.     Change in recruitment patterns – with a change in length tension relationships and the associated compensatory strategies, altered recruitment patterns can result over time.  Just like the pitcher who has developed bad throwing habits, if these are never retrained, then they can persist and ultimately add to muscle pain and/or contribute to or directly cause muscle strains.

c.     Weakness due to pain –pain occuring as a result of the movement patterns described above, can lead to weakness and atrophy of some of the supporting musculature of the lumbar spine.  In one study the authors found that the multifidus had a 25% decrease in cross sectional area with pain. They also found that the muscle must be retrained in order to regain its base level of strength and cross sectional area once the pain is resolved. [ii]   If the muscle is not retrained and the weakness remains, the area will be more susceptible to overuse and injury. 

In the following example we see an athlete who has been complaining of lower back pain as well as knee pain.  When assessing his functional movement with a squat, we see a significant lateral shift to the right.  With this degree of lateral shift, there is a significant increase in loading to the right knee and hip and also to the right lower lumbar spine. 

When evaluating this individual using other functional testing positions (such as the single leg squat) he continues to demonstrate these same pathokinematics with a loss of control at the hip.  This results in a significant amount of rotation at the hip and sidebending in the lumbar spine.  So again, we see increased loading to the lumbar spine resulting in increased stress to the facet joints and intervertebral discs.  Over time, this can result in disc bulges/herniations, spondylolysis (stress fracture) or spondylolisthesis (slippage), as well as low back strains and sprains. 

In this particular example, based on these and other tests performed in the physical therapy clinic, the athlete is, in fact, likely to be at risk for disc herniations and bulges, common athletic related spinal fractures and low back pain, as mentioned above.  Additionally, his performance will be drastically reduced due to weakness in the left leg which occurs over time due to the high degree of lateral shift to the right that he demonstrates.  Instead of having equal power output from the core down through the lower extremity in each leg, he will have less power output on the left.  In addition, the right side will have less power output than would be possible, due to a change in length tension relationships on the right, which is addressed in more detail in the next chapter.

In conclusion, whether they are seen at the foot or the spine, pathokinematics have a dramatic impact on the entire system.  Whether it is due to abnormal force attenuation, altered recruitment patterns or altered length tension relationships, pathokinematics can dramatically impact the kinetic chain causing pain and ultimately injury over time.  After reviewing the entire lower extremity, we can easily see why it makes sense that there would be an increased likelihood and a potentially increased magnitude of injury when pathokinematic movement patterns are combined with higher impact sports and those involving increased loads.

In addition, the research shows that the magnitude of the force that the body has to withstand with athletic activity ranges anywhere from 3 to 8 times body weight, depending on the type of surface and the sport.  Considering the amplitude of forces that the body must withstand with athletic activity, improving the efficiency of movement and the amount of force the muscles have to and are able to absorb, transfer, and manage is essential to reducing the potential for injury, as well as for maximizing power and endurance. 

If you like what you read the biggest compliment you can give to us is to share the passion.  Follow us on Twitter @ACL_prevention or on Facebook at Athletic Therapy Services.  Remember #MoveRight, last longer and perform better!

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

Athletes and Pathokinematics - Part IV - Hip

Throughout this series we have seen the impact that pathokinematics has on the lower kinetic chain   As described previously, we typically see pathokinematics in one or a combination of the following movements at the hip:
from the foot to the knee.  As we continuing to move up the kinetic chain, we see that pathokinematics impact the hip as they do the knee, foot and ankle and the structures inbetween.

1.     Hip adduction

2.     Hip internal rotation

3.     Trendelenburg (dropping of the pelvis on the contralateral side during weight bearing on the ipsilateral side).

If these occur in high loading situations or during high impact sports, the angles of the articulating surfaces can be altered, and the length tension relationships of the musculature supporting the hip/pelvis can change and/or we can see abnormal force attenuation on the tissues of the hip.  This can lead to several problems:

1.     Posterior and lateral hip issues – the hip (in general terms) is the articulation between the head of the femur and the acetabulum.  The bony architecture of this ball and socket joint allows for a tremendous amount of stability, while also allowing for some considerable range of motion in multiple planes.  There is also a significant amount of musculature that provides additional stability to the joint and which also provides motion.  The hip, like most joints in the body, is designed to be loaded in a particular fashion.  Moving outside of this “ideal” position, repetitively and under high loads, can result in tissue breakdown and degenerative changes in the joint.  With pathokinematics, we tend to see the femur in an adducted and internally rotated position along with trendelenburg at the hip.  One of these motions alone can add to increased stress to the tissues and musculature which is designed to resist these motions.  When in combination with each other and under high loads, this can cause lateral hip pain and conditions such as:

a.     Trochanteric Bursitis – the trochanteric bursa is a bursal sac located between the greater trochanter of the femur and the tensor fascia lata (TFL).  This is designed to reduce the wear and tear on the TFL from the bony prominence underneath (greater trochanter).  When there is increased tensile and compressive loads to this tissue (with hip adduction, trendelenburg and internal rotation) then the tissue will respond with inflammation.  Inflammation of this tissue is referred to as trochanteric bursitis and will present itself as lateral (or slightly posterior lateral) hip pain.

b.     Hamstring strains – the hamstrings cross two joints, the hip and the knee and are composed of three heads, the biceps femoris (lateral aspect), semimembranosus and semitendinosus (medial hamstring).  The hamstrings function to flex the knee and to aid in hip extension in a closed kinetic chain.  With excessive pathokinematics, the hamstrings are compromised in two primary ways:

                                               i.     Increased work - with trendelenburg gait, hip adduction and internal rotation, there is often accompanying gluteus maximus (GM) weakness.  If the GM is weak, especially in athletes whose sports require rapid acceleration (sprinters, soccer players, football players, basketball players) then the hamstrings will become over active in an attempt to assist with rapid hip extension.  Since the hamstrings are picking up part of the load traditionally provided by the GM, then the hamstrings can easily become overworked resulting in hamstring pulls, tears and ruptures.

                                             ii.     Increased load – with the same mechanisms above (trendelenburg, hip adduction, internal rotation) combined with increased force attenuation (since less force is absorbed at the foot/ankle and knee), the hamstring is put under an even higher tensile load and this can result in irritation.  If this irritation outpaces the body’s ability to repair it before the next work/loading session, this can again lead to an increased potential for hamstring pulls, tears and ruptures.

c.     Piriformis syndrome – the piriformis is a muscle deep in the hip that originates at the anterior   This muscle serves to provide some component of external rotation to the femur on the acetabulum and some component of hip abduction.  In a closed kinetic chain, this muscle is put under a tremendous tensile load when there is hip adduction, trendelenburg and internal rotation.  If these motions occur in the presence of weakness of the gluteus medius (which is a much larger muscle much more equipped to resist these motions) then the piriformis continues to attempt to resist some component of these motions without the support of the larger and more powerful muscle.  This results in the smaller piriformis muscle becoming overworked and strained.  When this muscle becomes strained, it w
ill typically present in one of the following ways:
sacrum and superior margin of the greater sciatic notch and inserts at the superior medial portion of the greater trochanter.

                                               i.     Deep posterior gluteal pain – with deep posterior gluteal pain, the piriformis will often develop a trigger point along with pain which radiates inferior or superior from that trigger point.  This most often will result in posterior gluteal pain which is increased in sitting.  If this is in fact the cause of posterior gluteal pain, it is easily diagnosed with a piriformis stretch in a sitting position.  Pain is elicited with the stretch and upon release of the position relief is provided.  We often tell patients, if this stretch is done correctly, you will experience slight pain during the stretch (we do not want to stretch to the point of significant pain) and relief from this pain upon release.

                                             ii.     Sciatica – the sciatic nerve is a nerve that originates from L4-S3 and runs the entire length of the upper and lower leg Sciatica is a term that is often over used in sports medicine and is often a catch all term for any pain which radiates down from the gluteal region to the lower leg.  With radicular symptoms, it is important to determine if this is coming from the lumbar spine, nerve root irritation or entrapment or compression of the sciatic nerve at the bifurcation of the piriformis.  For our purposes, we will use the term sciatica to describe conditions just related to the sciatic nerve.  With pathokinematics, the nerve is put under a tremendous amount of tensile load with excessive hip adduction, especially when combined with a trendelenburg.  If this occurs with high loading activities or occurs repetitively, then there is an increased potential for the nerve to become inflamed or compressed by the piriformis.  Since nerves are vascular tissues, this tensile load and/or compression will result in an inflammatory response by the nerve.  This will result in radiating pain.  When this is the result of entrapment or compression of the nerve from the piriformis, it typically starts as deep posterior gluteal pain (piriformis syndrome), then progresses to radiating pain that can radiate down to the lateral calf. Whether it starts as radiating pain or deep gluteal pain that radiates down the leg, identification and early intervention is critical to a quick recovery. 

                                           iii.     Deep posterior gluteal pain with sciatica – worst case scenario is the combination of both of the above conditions.  You will typically see this in the athlete who has been attempting to work through piriformis syndrome allowing it to progress to sciatica.  In extreme cases, this can involve lengthy rehabilitation which is easily exacerbated with some of the typical interventions we use.  Therefore, early identification and intervention is key to a quick and speedy recovery and return to sport in this case.

2.     Anterior hip issues – in discussion of the anterior hip, in particular the hip flexor, we will also briefly discuss deeper internal structures of the hip that are impacted with pathokinematics. 

a.     Deeper internal structures – the most common deep structures that are impacted with pathokinematics are the labrum of the acetabullum and the articulating surfaces between the femur and the acetabullum.  Although these are impacted with pathokinematics, they appear to be more impacted with repetitive high loading situations, especially when seen in combination with an increased magnitude and peak amplitude with each step imparted to the tissues.

                                               i.     Labral Tears – the acetabular labrum is a thick cartilage that runs the circumference of the acetabulum.  This structure increases the contact area and deepens the acetabulum which provides some increased stability to the joint.  The labrum of the hip, much like the labrum in the shoulder, is designed to mitigate compressive forces and will wear more quickly when combined with shear stresses.  The acetabular labrum is put under increased compression and shearing stress when there is the combination of hip adduction and internal rotation or trendelenburg.  In closed kinetic chain situations and with repetitively high loads, the labrum can tear.  This most commonly occurs on the anterior superior aspect of the labrum and will usually result in anterior groin pain.  Labral tears are often hard to diagnose and usually have to be done via magnetic resonance imaging.

                                             ii.     Early onset of degenerative joint disease (DJD) – the articular   Much like the articular cartilage of the knee, the articular cartilage of the hip is strongest under compressive forces and weakest when subjected to shearing forces.   Shearing forces imparted to the cartilage causes it to break down faster, crack and fissure and ultimately can lead to it being worn away completely, resulting in bone on bone articulation.  According to recent studies abnormal movement patterns may be the number one predictor of arthritic changes in the joint and can lead to total joint replacements later in life.  Wearing of the articular cartilage and early onset of DJD can result in anterior groin pain and crepitus (audible or palpatable grinding) in the hip.  
surfaces of the femur and the acetabulum are covered with articular cartilage which essentially allows for smooth and pain free range of motion of the hip.

b.     Hip flexor tendonitis – with the stresses that are associated with pathokinematics as well as some commonly seen tightness (lack of hip extension) and weaknesses (decreased hip extension strength), there is an increased amount of stress that is imparted to the hip flexors.  With pathokinematic movement patterns in particular, we also tend to see significant tightness of the anterior hip (specifically the rectus femoris and iliopsoas).  Increased tightness and associated decrease in hip extension, during sport related activities can increase the potential for a rapid over stretch of these muscles resulting in an inflammatory response.

Let’s take a look at an example.  Here we are looking at a black belt in karate complaining of hip pain and decreased ability to kick with significant force with the right leg.  This has been going on for some time and she is experiencing more and more difficulty participating in her sport as time goes on.  When looking at this athlete’s mechanics, she demonstrates a significant amount of adduction at the hip with a single leg squat as well as during other functional movements.   

Looking closely at the amount of adduction at the hip and the force vector represented in this picture, you can see that in this case, with single leg kicking activities, there would naturally be an increase in the amount of shear stress at the hip and particularly, increased tension to the structures of the lateral aspect of the hip.  This athlete is at risk for hip bursitis, hip arthritis, hip labral tears, groin strains and increased stress to the sacroiliac (SI) joint of the lower back.

In addition to risk of these types of injuries, this athlete’s kicking performance as measured by power output, force and torque, is compromised as she reports.  Pain and injury can be causative factors here, but also once again we see that the normal kinetic chain is interrupted and power is diverted away from the lower extremity (foot and ankle in this case) and instead is lost at the knee instead.  In this athlete’s sport, karate, it is critical to channel as much core strength through the entire chain and out at the point of contact with the opponent. 

Next week we will look at the impact these movements have on the lumbar spine and sacrum.  If you like what you read the biggest compliment you can give to us is to share the passion.  Follow us on Twitter @ACL_prevention or on Facebook at Athletic Therapy Services.  Remember #MoveRight, last longer and perform better!

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training.