A Clinical Trial to Compare Safety and Effectiveness for Relieving Tenderness of 10% Naproxen Gel vs. a 2.32% Diclofenac Diethylamine Gel in the Treatment of Strains and Bruises of the Legs.

Inclusion criteria

• Participant must be 18 to 60 years of age inclusive, at the time of signing the informed consent.
• Participants with a primary diagnosis of acute sports-related acute soft tissue injuries of the lower extremities that do not require hospitalization and that occurred within 3 hours of enrollment.
• Participants with a baseline algometric measurement values on the injured site of ≤50% of the respective value at the contralateral site.
• Participants with a baseline pain on movement (POM) of ≥50 mm on a visual analog scale (VAS) (0-100 mm).
• Participant's absolute sensitivity to tenderness on the contralateral site is at least 2.5 N/cm2 as measured by algometry.
• Participant's size of trauma is between 25 and 150 cm^2.

Exclusion criteria

• Heart surgery within 2 weeks of enrollment in the study.
• Suspected bone fracture or torn ligaments related to the injury.
• Open wounds to the area to be treated.
• Current skin disorders or localized infection in the area to be treated.
• Injured area is too hairy for proper assessments.
• Suspected head injury.
• History of blood coagulation disorders.
• Current or past history of gastrointestinal ulceration, gastrointestinal bleeding or other bleeding disorder(s).
• Relevant concomitant disease such as asthma (exercise induced asthma is permitted).
• History of significant disease deemed by the investigator to render the patient unsuitable for inclusion, including evidence or history of clinically significant (in the judgment of the investigator) hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular (including hypertension and cardiac arrhythmia), hepatic, psychiatric, neurologic diseases, or malignancies within the last 5 years.
• Participants with a medical disorder, condition, or history of such that could impair the participant's ability to participate or complete this trial in the opinion of the investigator.
• Significant ongoing painful condition other than that associated with the sports-related injury/contusion.
• Any ongoing condition that might interfere with the absorption, distribution, metabolism, or excretion of the study medication.
• Females who are planning to become pregnant, are pregnant or lactating. Prior/Concomitant Therapy
• Ice and compression are prohibited from the time of injury through the final evaluation.
• Physical therapy or other comfort measures, or herbal preparations for bruises from the time of injury through the final evaluation.
• Use of any medications within 5 days of enrollment until discharge from the study site (except oral contraceptives, prophylactic antibiotics, synthetic thyroid hormones, methylphenidate or medications to treat benign conditions such as antibiotics to treat acne).
• Any other treatment or medication (oral or topical), that could interfere with the trial (e.g. corticosteroids) up to 3 days prior to the trial.
• Participants with the following medical conditions may be eligible at the discretion of the investigator: ADHD on a stable dose regimen of methylphenidate/(dextro) amphetamine for at least 6 months; participants with hypothyroidism on a stable dose of synthetic thyroid hormone for at least 6 months.
• Have received any form of treatment in the form of medication for depression in the past 6 months or any form of psychotropic agent (including selective serotonin uptake inhibitors [SSRI] but excluding ADHD medications described above) within the last 6 months.
• Any previous history of allergy or known intolerance to naproxen, diclofenac, paracetamol or any of the drugs or formulation constituents which, in the investigator's opinion, might preclude use of an NSAID, including aspirin-sensitive asthma or a previous allergic response to a NSAID, including bronchospasm, urticaria, angioedema, and rhinitis; participation in a clinical trial in the previous 30 days.
• Use of any over the counter (OTC) or prescription medications with which the administration of naproxen, acetaminophen, any other NSAID, is contraindicated.
• Habituation to analgesic drugs including opioids (i.e., routine use of oral analgesics 5 or more times per week for greater than 3 weeks within the past 2 years).

Other Exclusions

• More than low-risk alcohol consumption (>24 g (males) or ˃12 g (females) of alcohol regularly per day). Amount corresponds to 0.6 L of beer/day or 0.24 L of wine/day or 3 glasses (at 2 cL) of liquor/day for males and 0.3 L of beer/day or 0.12 L of wine/day or 1 glass (at 2 cL) of liquor/day for females.
• Self-reported drug abuse within two years prior to screening.
• Member or first-degree relative of study staff or the Sponsor directly involved in the study.
• Unwilling or unable to comply with all requirements outlined in the protocol.
• Previous enrollment in this study.