Soft tissue is a term used to describe muscles, tendons and ligaments (not bone). Injury to these structures can include bruising, ligament or joint sprains, or muscle pulls ranging from a minor strain up to a complete tear or tendon rupture. These injuries are very common, and may be caused by an accident (such as a trip or fall), or a sudden change or increase in an activity which can overload the tissues and cause them to become inflamed (eg. spending all day in the garden, or starting running after a long break).
Please see the advice sheet about the self-management and recovery from sprains and strains. You may also wish to refer to the specific section for the joint involved for further advice regarding exercises and when to access specialist assessment.