 Eligible patients will be randomized in a 1:1 ratio to receive double-blind treatment with either the diclofenac topical patch or a matching placebo patch to be applied once daily for 14 days. Patients will return to the clinic for assessments on Day 3, Day 7 and Day 14; a follow-up assessment will be conducted on Day 21. Patients will complete an electronic diary in which assessments including pain intensity and pain relief will be recorded twice daily. Functional disability and global impression of change will be recorded in the diary at study visits, ratings of the quality of sleep will be recorded in the diary each morning, and the use of study treatment and rescue medication will be recorded in the diary each day. 