The knee is a relatively complex joint considering its hinge based status and primary flexion/ extension movements. Placed between two multi-axial joints which can be quite unstable, the knee can often feel the brunt of non-contact injuries associated increase forces from poorly controlled hip and ankle joints. The most common of these injuries is ACL tears or ruptures which we touch on in the previous article: ACL Injury: No Longer a Career Ending Injury.
Identifying the areas which may be contributing to increased stress is important factor for the rehabilitation process and patient management. In many cases the question asked “but which do address first, the foot or the hip?” My initial answer to this question is to address the feet first. This is not a decision I chose because I am a podiatrist but more so on the fact that the issue surrounding the feet and ankles can be addressed in a faster amount of time initially, leaving you and your patient more time to focus on the exercised based rehabilitation program of the hips.
The evaluation of an individual’s biomechanics during running has the potential to identify risk factors, which may contribute to running injuries. However, any injury as a result of biomechanical movements is not solely based on the action itself, but the body’s ability to cope with the forces placed upon that tissue.
The transition from walking to running may bring increased ground reaction forces, rotation moments and impacts upon the knee due to the nature of the activity and its single leg stance. For this reason, it is important to be aware of where the activity of walking finishes and running/jogging begins. The change of walking to running occurs when double support (both legs in contact with the ground) stance phase during the gait cycle ends and two phases of double legged float begins (NOVACHECK, 1998).
At the moment of ground contact when the foot becomes fixed to the underlying surface, a moment of dorsiflexion begins to take place at the ankle. This moment induces internal tibial rotation and pronation around the oblique axis of the sub-talar joint. That pronatory moment is responsible for the “unlocking” of the once stable foot to act as a better absorber. However, due to this moment, rotational torques are transmitted through the tibia with potential for forces to be felt more proximal at the knee joint.
As the foot enters an its propulsive stage of gait the foot will supinate, regaining its stability or “locked” position to act as an effective lever before toe-off.
A number of studies have looked at the motion at the hip during running. At the time the foot makes contact with the ground the hip is in an adducted position which then progressively becomes more adducted as the foot enters the shock absorbing stance phase. Then from stance through to toe-off the hip becomes more abducted as it looks to aid in the “triple extension” moment.
And this is where we look at the impact of both those structures on the knee. Both the ankle joint and the hip joint are multi-axil structures designed for mobility. Our knee on the other hand is perceived as a joint for stability, a hinge joint with the two primary movements of flexion and extension, a joint that has specific anatomical structures in place for the limitation of movements such as adduction/abduction and internal/external rotation.
Now imagine if that poor knee joint was unlucky enough to have a runner who had not only poor pelvic/hip control but also chronic instability at the ankle joint as well, and the amount of force attenuation required to cope with those moments that occur simultaneously.
This is where my previous statement comes into play regarding the use of orthotics for knee pain associated with both the foot and the knee. In an ideal world a patient would be given a minimum of three exercises for each area of concern to improve activation, control and strength of those areas so no offloading or bracing is necessary. However, in being able to truly achieve that outcome, there is a large amount of confidence required in the patient’s compliance to the prescribed tasks, their ability to complete these tasks with the correct technique and will be able to maintain these assets over an extended period of time.
Or alternatively, an offloading device is used to help with the attenuation of forces which are occurring at the foot, while exercises related to the larger proximal muscles are prescribed. As activation and control at the hip reaches an appropriate level, orthotics can be weaned from the patient and foot/ankle exercises deployed, potentially returning a patient to sport earlier than may have previously be possible with the previously defined ideals.
Until Next Time
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