Dispelling the Myth: Importance of Mechanics from the Ground Up
By Robbie Ohashi PT, DPT, OCS, ATC, CSCS
Biomechanics is best described as an interface between muscular and neurological activity. When biomechanics are sound, the movement system runs efficiently with minimal stress experienced by the involved tissues. However, just the opposite occurs when the biomechanics of the movement system are dysfunctional.
It is generally accepted amongst rehabilitation and performance training professionals that repetitive faulty movements result in microtrauma to the tissues. If the tissue’s healing response is insufficient, repetitive stress can lead to macrotrauma and eventual musculoskeletal pain syndromes. This is often the case in repetitive use injuries of the lower extremities. In treating these chronic lower extremity conditions, the question remains — does one best address faulty biomechanics from the top-down, or the ground-up?
The easy answer to this question is that you need to address both. The importance of proper foot stability and ankle mobility cannot be neglected as an integral part of the kinetic chain. However, it is my contention that the evaluation and intervention of the lower extremity should start proximally with the pillar.
The dynamic relationship of the three components of the pillar, the scapulae, trunk and pelvis provide a stable platform for the upper and lower extremities to operate from. Recent research has clearly linked deficits in both core stability and hip strength (primarily the hip abductors and external rotators) with repetitive lower extremity injuries.
One reason for the emphasis on the proximal segments is that the large joint reaction forces the muscles of the hip to counteract to maintain equilibrium in the movement system. Neumann reports that in the static position of single leg standing, the moment arm used by the hip abductor muscles is about half the length of the moment arm used by body weight. Therefore, to achieve frontal plane stability in this position, the hip abductor muscles must produce a force about twice that of superincumbent body weight. He reports that data based on computer modeling or direct measurements from strain gauges implanted into a hip prosthesis indicate that joint reaction forces reach at least three times body weight while walking and up to 5-6 times body weight while running or ascending and descending stairs. The thought of the forces required by the muscles of the hip to generate to counteract joint reaction forces during deceleration or changing direction from a full sprint is mind-boggling.
The hip joint acts as the most proximal link in the lower extremity kinematic chain, provides multi-planar motion and utilizes a complex set of muscles for movement and stability. Impaired muscle performance of the hip can lead to dysfunction in all planes, most notably the transverse and frontal planes with excessive hip adduction and internal rotation. This faulty movement pattern of the hip is associated with a state of altered mechanics of the distal segments as well, including medial collapse of the knee, tibiofemoral joint rotation, lateral tibial rotation, and pronation or supination of the foot. It is also a major contributing factor in multiple repetitive use injuries such as patellofemoral pain, Iliotibial band syndrome, piriformis syndrome, internal derangement of the knee and medial collateral ligament sprains, amongst others.
Addressing only the distal foot and ankle complex in an athlete with this pattern of dysfunction may cause more harm than good. For example, an athlete with long-standing hip abductor and external rotator weakness and a knee valgus collapse can have resultant foot pronation and a chief complaint of plantar fasciitis (see Pictures A & B). A common intervention for this hypermobile, pronated foot is to add a stabilizing, rigid foot orthotic to the athlete’s shoe. However, only treating the movement dysfunction at the distal segment without eliminating the true source of the pain through correcting the athlete’s proximal hip mechanics, may lead to increased microtrauma and pain at the knee joint as the femur now internally rotates on a newly fixated tibia.
Because of their relationship with lower extremity injuries, the dynamic stability of the proximal components of the lower extremity including the trunk, pelvis and hip, must be a priority in both rehabilitative and performance-based programs. This is especially the case with activities promoting single leg stability. While the mobility and stability of the distal segments are important to the entire kinetic chain and should be addressed, in most cases they should take a back seat to the proximal components of the pillar.
The Athletes’ Performance Lower Quarter Functional ExaminationREAD MORE provides rehabilitation professionals a system to identify and treat these impairments of the movement system. This is often the crucial first step in eliminating the cause of an athlete’s lower extremity pain, increasing their performance potential, and lengthening their competitive career.
Picture A: An athlete with the diagnosis of right plantar fasciitis and a pattern of dysfunction including compensatory hip adduction/internal rotation, tibial lateral rotation, and foot pronation.
Picture B: The same athlete after being cued to engage her hip abductor/external rotator muscles and point her feet forward. Note how the alignment of her distal segments is improved by correcting the proximal segments of her lower extremities.