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Joint Stability - 1 Muscular Arrangement o Muscles cross...

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Joint Stability: Joints allow movement, however, too much movement means instability. Joint cohesion = resistance to displacement Movement is gained at the expense of stability Factors Influencing Joint Stability: 1. Shape of the bony structure; o A hinge is more stable than a saddle o The hip ball and socket joint is more stable than the shoulder due to it’s depth and bony structure 1. Ligaments ; o not very elastic, strong, fibrous tissues o connect bones and help maintain their relationship o they check movement at the extremes o are easily torn in violent motions they are very resistant to fast stretch o however, can over-stretch if subjected to prolonged stress o ligaments do not easily recover to their previous length when stretched, therefore, joint stability can be permanently affected
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Unformatted text preview: 1. Muscular Arrangement; o Muscles cross joints and, often, when they shorten, they provide good joint support by pulling one bone into the other at the joint (causing joint compression). Consider the line of action of each muscle as it pulls on the bone…. examples - Shoulder - subscapularis, supraspinatus, infraspinatus, teres minor. Knee - quadriceps and hamstrings. 1. Fascia and skin o provide a capsule to hold the joint structure together 1. Surface tension (negative pressure) o Congruent bone surfaces which are covered in synovial fluid strongly resist being pulled apart because of the surface tension of the fluid o especially in the hip joint - the ball is held in the socket by surface tension and atmospheric pressure...
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