Mobility is important to us
We all know that our mobility is one of the most important things to us. Without it, we are constrained to our home unless someone is able to take us out. As younger people we injure ourselves in sports or leisure activities and this can result in an end to our career in sports if not treated or rehabilitated correctly. As we get older we start to suffer from hip and knee osteoarthritis which is so painful that we can’t walk. Eventually we get a joint replacement but in many cases the outcome is not good and we don’t resume normal mobility. And then in our later years we have a fear of falling because we know how important it is for us not to fall over. Unfortunately this fear often leads to poor walking habits which result in a fall.
So how can we improve the situation? In all cases, knowing what the problem is helps us put it right. It is a little like having high blood pressure. We know how bad it is, we take corrective action and then we check that the corrective action is working.
The limitations of the human to assess walking
Skilled people believe they can see things and so we can do the assessment themselves. Unfortunately, this simply isn’t the case, which is why so many people don’t recover from injury or surgery or fall in later life.
Watch a person walking down the street and what do you see? You see their body movement and their arms swing, but you don’t see the legs moving. Why not? Well, there are many reasons, and they are all to do with how quickly our eyes take images, how detailed these images are and how well our brain can process these. Imagine we are a video recorder and a computer combined. The video is our eye and the frame rate is quite slow, around 20Hz. That means for every stride we have 20 images. Furthermore, when we work at this frame rate we only take in a limited amount of the image for processing, typically the outline form of the complete body. So, we have 20 images of the human form to work with. From this we want to see the limb movement as this is how we propel our self forward. In practice, this is impossible. The human brain cannot look at an image and get a position of individual limb segments, rather it stores the overall body position.
What information we need
In order to assess gait we need absolute position of all limb segments in relation to each other about 100 times per second, in order to get a detailed profile of how we are moving our limbs. This needs to be in the sagittal and coronal plane against a reference axis and must be accurate to within a degree. We then need to store these 100 frames, with the absolute reference axes and process them to produce differences between the frame, in order to formulate the gait cycle in terms of limb movement. Then we would have a 100 point curve for the limb segments per stride. From this we can also calculate how the joints are moving through the gait cycle.
How does this information help?
Walking problems may be due to injury, conditions such as knee osteoarthritis (OA) or lack of muscle strength. In all cases we adapt the way we walk in order to minimise pain and we often do this without realising, for example with early stage knee OA. This adapted gait cycle can provide an early warning indicator which enables conditions to be treated early. In the case of injury, the problem is known, but the gait cycle identifies how well the recovery process is working. And for lack of muscle strength the gait information shows the severity and how well the person is responding to exercises.
Without precise information conditions such as knee OA are only detected once pain is significant (late stage) by which time often the only treatment available is joint replacement surgery.
Recovery after surgery is slow and painful and for some people there is insufficient incentive to continue, resulting in a permanent lack of mobility.
Incentive is important in anything we do, particularly where pain is involved. Accurate information on how you are walking shows the slow improvements and hence provides the incentive to keep going.
There are numerous sufferers of lower back pain, who simply do not know what is causing the pain. In some cases the pain may be due to a gait deficit that is causing compensatory back movement. So whilst the limbs are hurting the back is. Monitoring of the walking pattern can identify whether the problem is due to walking incorrectly or whether it truly is a back problem.