anything that will cause scapular instability, e.g. wry neck + holding arms infront of body for long periods (musician, typist, hairdresser, awning installer) + changed breathing (pregnant, reaction to medication, putting on weight causing pressure on diaphragm) + work hardening program, truncal strenghening program+laying on back for extended periods.
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if the person gets a wry neck and doesnt have an exacerbating factor they are likely to recover. if there is an exacerbating factor that doesnt allow the scapular instability to resolve, it is a slippery slope into the abyss. regards towelhorse