RUNNING INJURIES

Causes of abnormal pronation Problems associated with abnormal pronation

Limb length discrepancy (LLD) Genu valgum & varum (knock knees

and bow legs)

Tibial valgum & varum, forefoot inversions, ankle equinus

Overuse injuries, medial knee pain Patello-femoral disorder, achilles

tendinopathy Plantar fasciitis, stress fractures Table 1: Some of the common causes and problems associated with abnormal pronation

Causes of abnormal supination Problems associated with abnormal supination

LLD, genu varum, tibial varum Subtalar joint varum Orthoses and plantarflexed 1st ray

Decreased shock absorption, osteoarthritis

Stress fractures, lateral knee pain

Ilio-tibial band syndrome, lateral ankle joint sprains and instability, digital deformities

Table 2: Some of the common causes and problems associated with abnormal supination

It is beyond the scope of this article to cover full biomechancial evaluation howev- er the ‘Further reading’ section at the end of the article lists recommended texts detailing biomechanical assessment of the foot.

Gait cycle During locomotion, one full gait cycle is the interval of time from heel strike of one foot to heel strike by the same foot at the next step. The gait cycle is divided into a

stance phase and a swing phase period for each foot. The stance phase portion of the gait cycle, for each foot, occurs between heel strike and toe off.

During the swing

phase, the foot swings from one step to the next and is non-weight bearing. The swing phase requires approximately 38% of the full gait cycle.

Running cycle Stride length and stride rate tend to increase with increases in running speed.

Walking Contact (27%)

Stance phase (62%) Midstance (40%)

Swing phase(38%) Propulsion (33%)

As a rule, uphill running tends to shorten stride length and increase stride rate while downhill running tends to lengthen the stride length and decrease the stride rate. Heel strike is the most common of initial ground contact but some runners may strike the ground with either their midfoot or the forefoot.

The magnitude of the

ground reaction force (GRF) is greatest dur- ing the contact phase and increases with increased speed. It is estimated that in a 70kg man each foot will endure 1,000,000 kg of force over a marathon distance and it is therefore, hardly surpris- ing that in a biomechanically compromised runner, injury risk tends to be greater.

Functional foot orthoses Functional foot orthoses are an orthopaedic device which are designed to promote structural integrity of the joints of the foot and the lower limb by resisting ground reaction forces that cause abnormal skeletal motion to occur during the stance phase of the gait cycle. There are three main biomechanical con- cepts concerning the control of abnormal biomechanical compensation with func- tional foot orthoses:

1. The orthoses ensure that the subtalar joint is as close to its neutral position as possible just before the foot enters the propulsive phase of the gait cycle ie. prior to heel raise

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30% Figure 1: Comparison of the walking and running cycles SportEX 25

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