Joint stability

The ability of a joint to withstand mechanical shocks and movements without being dislocated or otherwise injured. Stability depends on a number of factors, including the strength of the ligaments that bind the bones together, and the strength of muscles associated with the joint. Excessive flexibility training, especially without appropriate strength training, may reduce stability making an individual more prone to dislocations.

The ability of a joint to withstand mechanical shocks and movements without becoming dislocated or otherwise displaced and injured. Stability is provided by the support of the surrounding bones (osseous stability) and the soft tissues, including the joint capsule. ligaments, and muscles. Stability varies according to whether the joint is moving (dynamic stability) or stationary (static stability). The bones contribute mainly to static stability; the ligaments and capsule to both static and dynamic stability; while the muscles contribute only to dynamic stability. Different joints vary greatly in their stability; different types of stability may vary within a single joint. The hip, for example, has a high osseous stability, while the knee has a low osseous stability, but high ligamentous and muscular stability. Excessive flexibility may reduce stability and make an individual accident prone.

Joint stability refers to the resistance offered by various musculoskeletal tissues that surround a skeletal joint. Several subsystems ensure the stability of a joint. These are the passive, active and neural subsystems.^[1] The opposite of stability is instability. It is believed that one or more of the subsystems must have failed if joint instability occurs.

The bony components that may relate to the potential for joint instability can be measured by use of x-rays. Plain film lateral x-rays can be used to evaluate for translations anteriorly (anterolisthesis) or posteriorly (retrolisthesis). Where plain films indicate the likelihood of these translations being significant, flexion-extension views can be utilized to determine the dynamic range of movement of joints. This allows for a more accurate view of any potential instability issues.^[2]

References

1. ^ Panjabi MM. (1992). "The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis.". J Spinal Disord 5 (4): 390–7. doi:10.1097/00002517-199212000-00002. 
2. ^ Cocchiarella, L.; Andersson G. (1993). American Medical Association Guides to the Evaluation of Permanent Impairment, Ed 5. Chicago Il. USA: American Medical Association. pp. 98. ISBN 0-89970-553-7. 

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