A Study to Evaluate the Safety and Efficacy of CNTX-6970 in Subjects With Knee Osteoarthritis Pain.

A subject will be eligible for study participation if they meet all of the following criteria: 1. Individuals between 40 and 90 years of age (inclusive) at the time of the Screening Visit. 2. Willing to use a mobile smart device during the study period. Individuals who do not have access to a mobile device will be provided with one for the duration of the study and trained in its use. 3. Can understand the nature of the study and protocol requirements and is willing to comply with study drug administration requirements and discontinue prohibited concomitant medications. 4. Radiography of both knees with a posterior-anterior, fixed-flexion view taken during the Screening visit. The Index knee must show evidence of chronic OA with a K-L Grading Scale of 1, 2, 3, or 4. Such evidence will be provided by a central reading of the radiography of both knees from an expert radiologist of the CCC of EPPIC-Net. 5. Moderate to severe pain in the Index knee associated with OA and stable for a minimum of 6 months prior to Screening in the opinion of the investigator. 6. Confirmation of OA of the index knee: American College of Rheumatology (ACR) diagnostic criteria. 7. Subjects must have failed 2 or more prior therapies. Failure is deemed to be inadequate relief in the opinion of the investigator. 8. Body mass index (BMI) of ≤ 40 kg/m2. 9. Willing to refrain from illicit drug use during the study, and to have illicit drug testing at screening and at later time points. A subject will be e…