Home Search Sitemap Contact Bookmark

Free Dissertations - Health Dissertations

These Comparatively Simplistic Analyses Have Been Progressively Improved ...



These comparatively simplistic analyses have been progressively improved through the work of Kleissen and others (Kleissen R F M et al. 1998) who evolved the concepts of the foot as an adaptable, dynamic structure which adapts to uneven terrain as well as acting as an efficient shock absorber for the stresses and strains encountered during walking, running and jumping.

In practical terms, it is appropriate to consider the foot as having elements of both types of function in combination as the stability and rigidity of the foot changes in different phases of the gait cycle. The mid-tarsal joint is the prime consideration in this respect as it varies in mobility through its ability to lock and thereby transform the forefoot into a rigid structure

Different authorities describe the gait cycle in different terms and may vary in detail. In this dissertation we shall give a brief overview of the main biomechanical features of the cycle.

The cycle is generally described as having four main phases, the heel strike, midstance, toe off (or propulsive phase) and swing through phases. We shall consider each phase briefly.
In the heel strike phase, pronation is the predominant movement. This occurs primarily through the alignment of the articular surfaces of the calcaneum and talus. In relation to the lower leg the foot is everted, dorsiflexed and adducted. At the point of heel strike, the mortise joint of the ankle becomes locked. Effectively fixing the talus and thereby causing all subsequent motion to take place at the sub-talar level. (Sadeghi H et al. 1997).

The musculature involved at this stage of the cycle are the long extensors of the lower leg which decelerates the action of plantar flexion, gastrocnemius which decelerates internal rotation of the tibia and tibialis post. which decelerates pronation. (Valmassy R L 1996)

Directly after the heel strike the mid-tarsal joint unlocks and allows the foot to transform from a rigid lever type structure to a dynamically mobile one. (Perry J 1992). This degree of mobility is short lived as the foot returns to its rigid configuration at about the midstance phase due to the locking of the mid-tarsal joint at the time when the metatarsal rays make initial contact with the ground and the beginning of the supination phase. As supination progresses so the mid-tarsal joint becomes locked. (Scholhorn W I et al. 2002).

In terms of biomechanics, we note that it is particularly during this phase of the cycle that the various proprioceptive mechanisms quickly determine and process information relating to the consistency and disposition of the walking surface and set up compensatory movements in other muscle systems in the body to maintain posture. (Rompe J D et al. 2003).


Thanks