The treatment intervention will be delivered in the physiotherapy outpatient departments of Worthing Hospital or Southlands Hospital. Treatment will be delivered by NHS physiotherapists over 13-15 weeks and consist of 6-8 sessions of physiotherapy. The first 4 sessions will be delivered weekly and the subsequent 4 sessions will be delivered every 2 weeks. This treatment dose and duration is consistent with previous high quality studies (Holmgren et al. 2014, Bernhardsson et al. 2011). The intervention will be delivered while patients are on the surgical waiting list for subacromial decompression surgery. The current waiting times for surgery vary considerably between consultants, from 18-28 weeks. This means the intervention can be fully completed during the waiting time for surgery.