Shoulder impingement syndrome is a very common cause of shoulder pain and normally treated with physiotherapy or surgery. Research has shown that physiotherapy is as effective as surgery, however, the incidence of surgery for this condition is on the rise internationally, nationally and locally. The most effective form of physiotherapy, however, is not known. Laboratory studies have suggested that posterior shoulder tightness may contribute to irritation of the soft tissue around the shoulder joint and perpetuate pain from shoulder impingement syndrome. There is a lack of good quality evidence to support this perspective. The aim of this study is to assess the feasibility of conducting a randomized controlled trial to evaluate the effectiveness of treatment for posterior shoulder tightness in combination with 'best care' compared with 'best care' alone in individuals with shoulder impingement syndrome.