Inclusion Criteria:  Willing to provide written informed consent; Male or female, 6-11 years old; 12-16 years old; or 18-45 years old; BMI <32kg/m2; Minor soft tissue injury within 96 hours of enrollment; Spontaneous pain of at least moderate intensity (i.e., pain of at least 6 on the Wong-Baker FACES® scale) according to the participant); Clinically significant injury according to the principal investigator; Willing and able to accommodate study requirements for data collection, including return for study Visits 2 and 5; Have access to high-speed internet, a computer, iPad, or android device for telehealth visits; Negative urine pregnancy test at inclusion for females of reproductive potential (started the menstrual cycle); For pediatric and adult females of reproductive potential (started the menstrual cycle): abstinence from sexual intercourse, or use of highly effective contraception for at least 30 days prior to screening, and agreement to use such a method during study participation and for three (3) days following the final topical system application; For pediatric and adult males of reproductive potential: abstinence from sexual intercourse, or use of condoms or other methods to ensure effective contraception with partner during study participation and for three (3) days following the final topical system application; and Able to read and speak English.  Exclusion Criteria:  Major soft tissue injury (fractures are only exclusionary if the injury is stabilized with a device, e.g., a hard cast, that cannot be removed to allow a topical system to be applied to the injured area); Open skin lesion or any dermatological condition (e.g., skin infection, eczema) within the injured area; Injury involves the spine, digits, hands, or bottom of foot; Prior injury to the same site within the past 90 days; Three or more other prior injuries (minor or major) to the region in the past; Injury occurred more than 96 hours prior to study entry; Prior use of topical medication to involved area within 48 hours of study entry; Hypersensitivity disorders, including asthma or urticaria, but only if associated with exposure to aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) including diclofenac; Coagulation defects; Prior use of over the counter (OTC) analgesics or short-acting NSAIDs (ibuprofen, ketoprofen) within 6 hours of study entry (acetaminophen permitted up until the time of study entry); Prior use of narcotic analgesics within seven (7) days of study entry; Prior use of systemic anti-inflammatory steroidal drugs within 60 days of study entry; Prior use of long-acting NSAIDs such as piroxicam or naproxen since injury; Concomitant use of drugs which may be susceptible to interactions with diclofenac, or affect safety if used concomitantly (e.g., serotonin-selective reuptake inhibitors, lithium, digoxin, anticoagulants, antidiabetic agents, cyclosporin, methotrexate, quinolone antimicrobials, other NSAIDs, steroids and diuretics); Participants with mental, behavioral, or neurodevelopmental disorders for which the relevant disorder(s) prevent compliance with the protocol; Documented alcohol or drug abuse within 365 days of study entry; Documented nicotine dependence within 365 days of study entry; Current or prior history of severe cardiac, renal, or hepatic impairment or disease; Severe systemic diseases (e.g., cancer, severe acute infection); Any underlying disease or medication that severely compromises the participant's immune system; Current or prior history of any chronic pain disorder; Current or prior history of gastrointestinal bleeds or, ulcers; Females who are pregnant or breast feeding; or Participation in another clinical trial within 90 days of enrollment.