How to Identify Pathological Movement - Part I

Throughout the last several months, we have been describing the impact poor movement has on injury risk and athletic performance.  Throughout this series, we will describe several ways to assess movement that will allow you to identify pathokinematics in yourself or athletes you work with, as well as what implications your findings might have for athletic performance or possible injury in the long run.  Whether you use the most recent technology like software that can be used to measure joint angles or basic visual observation, these tests will tell you specifically which movements are causing break down in the kinetic chain which is likely to decrease performance and cause injury to bones, tendons, cartilage, ligaments, and other soft tissue over time.  Specifically, these movement assessments will indicate where there are weaknesses and/or where there is tightness in the body which can result in pathokinematics.  

In this series, we will give you detailed, progressive exercises to address specific muscle weaknesses or tightness identified in the assessment process.  Properly assessing and applying the proper exercises is KEY to decreasing the potential for injury and for improving athletic performance.

It should be mentioned that the assessments included here are not intended to replace a comprehensive orthopedic examination.  These tools should be used for the purpose of assessing movement patterns only.  For a through orthopedic examination of the lower kinetic chain, see one of our specialists at a PhysioSports clinic near you.  For more information, visit www.myphysio.com for a clinic near you.  What you can expect during an extensive orthopedic assessment is for your physical therapist or athletic trainer to assess the entire kinetic chain including the quantity and quality of hip motion, full lumbar motion, as well as segmental mobility of the lumbar spine, the foot and the ankle.  This comprehensive examination is intended for use with people who have a previous history of injury, have existing injuries or those requiring a formal physical therapy intervention, and should only be done by a qualified health care professional.

Biomechanics Lab

The biomechanics lab can be considered the “gold standard” for movement assessment.  Most biomechanics labs use a Viacom (or similar) 8 or 10 camera system to view and measure movement patterns in the human body.  In the lab, analysts place markers on the subject and video tape movement from 8 or 10 different angles.  This movement is then digitized and can then be reproduced in a three dimensional model (picture).   Viewing movement in a three dimensional model allows you to see it from several angles which enables assessment of all of the connecting components of the movement.  Extremely accurate measurements can be taken during any phase of the movement, from which researchers and clinicians can determine hip, knee flexion angles, tibial rotation and many other components of movement which can lead to diagnosis of potential areas for performance improvement, injury prevention and/or injury rehabilitation.

Unfortunately, access to biomechanics laboratories is limited for most people since there are not many of them currently available in this country.  Labs are typically found in high performance centers, research or university settings only.  Building and operating a biomechanics lab is very expensive, typically costing anywhere from $200,000 to $500,000 depending on the number and types of cameras, force plates, and other equipment used in the facility.  With this high cost, many providers of outpatient physical therapy, athletic performance enhancement training and injury prevention services are prohibited from providing full laboratory access.

3D Technologies

There has been a recent influx of various 3D technologies available on the market and all of which say they can accurately measure and quantify movement in three dimensions.  This discussion here will only touch on each of these technologies and our experience with each and for more in-depth information on each, you can visit their individual websites. 

Xbox One Sensor - Some of the most affordable systems are those that are using the Microsoft Kinect.  In 2013, Microsoft released the new Kinect (Xbox One Sensor).  This sensor has had a lot of technological developments, one of which is the ability to track movement of the body segments.  This technology is great and a useful tool in movement assessment however, there are a lot of limitations.  As with any technology, we must be aware of the limitations so that we can limit the impact on what we are attempting to accomplish with it.  Some of those limitations include:

• Accuracy of the skeletal tracking
• Sensitivity to lighting which impacts accuracy of the tracking
• Significant artifact in the skeleton when measuring joint angles and movement.

One additional question arises is the 3D motion that is being measured truly 3D.   For example, you are not able to measure femoral rotation with this device and the majority of movement we were able to quantify with some degree of accuracy was frontal plane motion only.  That said, although this technology will improve over the years, some of the claims being made by some companies utilizing should be investigated.

Noraxon Myomotion – This is truly a 3D system that utilizes both 2D video and wearable sensors to detect motion in three planes.  Multiple myomotion system sensors are strapped to the subject after which the subject can perform the activities.  The system records the motion in three dimensions and displays these as both graphs and as skeletal movement.  This system has been found to be very reliable and accurate both for measurement of frontal plane motion and internal rotation of the femur.  It’s multi-functionality also allows it to be used indoors and outdoors but also has some limitations.

• Sensors – there are upwards of 5 to 10 sensors that can be placed on a subject.  Although this is great for data this can be someone less efficient.
• Sensor placement – the current strapping that is used with the sensors is not conducive to performing athletic activity without significant reinforcement (additional taping).  The sensor straps tend to move a lot and sometimes fall off.
• Distance from the hub – if you are performing athletic activity on the field, the distance you can get from the hub (which receives the signal from the sensor) is very limiting.  If you go outside that, you must stop and recalibrate the system.
• Efficiency – all the above mentioned issues leads to decreased efficiency.  An examination that should take 15 min ends up taking 45 min to one hour.

This system is very accurate but unfortunately it is very costly and cumbersome to use.  At a price tag above $20K and inability to use this efficiently in a clinical or in physicals makes it less than optimal. 

DorsaVi – This is a new wearable sensor technology out of Australia developed by a physical therapist.  This system also measures movement in 3D and uses a combination of both 2D video and a wearable sensor.  These sensors have an accelerometer, gyrometer and magnetometer.  This allows you to get force data, position data and rotational data.  The system records the motion in three dimensions and displays these as both graphs along with the 2D video.  This system has been found to be very reliable and accurate both for measurement of frontal plane motion and internal rotation of the femur.  Its multi-functionality also allows it to be used indoors and outdoors but also has some limitations.

Sensors need to be placed on exact anatomical locations – DorsaVi does provide training video and a device to aid in measurement and accuracy of placement.

• For ballistic movements, sensor has to be reset after each repetition – this can prolong time between multiple reps
• Movement specific – the system is locked in to specific movements that are set as a part of the software.

This system is very affordable and the company is working on many of the issues that impact its efficiency.  The beauty of all these 3D technologies is the ability for automated reporting.  This reduces 30-45 minutes of data analysis and writing a written report at the conclusion of an assessment.

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.