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:
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.
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.
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.
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