For Participants


Welcome to the A2CPS Participants’ page. This groundbreaking study would not be possible without your important contribution. Here you’ll find more information about the study timeline and what to expect at your clinical visits, as well as contact information and parking instructions for each clinical site. There’s also a message from Errol Patterson, our Patient Representative, along with his personal advice for those undergoing knee replacement surgery. Check out these outside pain resources we’ve put together, and soon you can catch up on all things A2CPS at our news page. Finally, don’t miss the message of thanks from the National Institutes of Health (NIH), which funds this landmark study. For more general information about the study, please visit our A2CPS Homepage.


Study Timeline

What to expect at each step of the study

Clinical Sites

Contact information and parking instructions for each site

Pain Resources

Links to additional, external resources on chronic pain

Patient Representative, Errol R. Patterson

Errol R. Patterson lives in Silver Spring, Maryland. He is married, has three children and two grandchildren. Mr. Patterson had an illustrious career as a trial lawyer in Washington, D.C., that spanned 30 years. He would go on to teach law at Georgetown University, but his lifestyle had slowed down enough by early 2017 that he knew the time had come: his knees needed replacing. In 2019, he signed on with NIH as the A2CPS Patient Consultant - someone who helps us better understand your perspective as participants as we set up and carry out the study.

“The study has been developed from the beginning with the patient in mind,” says Patterson. “We tried whenever possible to minimize the patient burden, to make it accessible and a positive experience overall.” For example, Errol advocated from Day 1 for participants’ incentives “to be adjusted to make them meaningful and send the right message to patients: that you value them.” Furthermore, he has argued for patients to be viewed as a community rather than simply as a collection of individuals.

Having gone through double-knee replacement himself, Patterson says he has tremendous respect for the A2CPS participants who are taking on the extra commitment of the study while juggling recovery and their other responsibilities. It’s a worthy effort, he says. “Everyone should understand the ultimate goal: that is to develop a profile of data that’s predictive of people who move from acute pain to chronic pain. Success in achieving that goal would represent a significant leap forward in the treatment of chronic pain. At the end of this landmark study, people may look back on it as a watershed moment. The knowledge that you’re a critical part of this history should give you great pride and satisfaction from helping your fellow man.”

Errol’s Recovery Advice

Patterson has some words of encouragement – and advice – for recovery from knee replacement surgery. Patterson is not a medical professional; please consult with your own physician for guidance on your own surgery and recovery.


If you’re considering knee replacement, “I would encourage people to go ahead with it at the first opportunity they can. Don’t wait; it can be a life-changing event.” Today, Patterson says he’s fully recovered, and back to living a full life. “My knees aren’t holding me back.” Of course, that’s not everyone’s experience, and some people may face additional barriers to surgery.


Looking back, Patterson says, “I didn’t have a full appreciation of what postsurgery was going to be like. I needed to be dependent on my support network.” In the days after surgery, “there’s a substantial need for somebody to be there for you.”


Without robust physical therapy, Patterson says, “you don’t get the full benefits of surgery. I can attest to that fact from my own experience, but also from others who had a less positive, successful experience.” And PT should be consistent, often three days per week. “Even when it’s hard, you just grind through it.”


Most people need at least some opioid medication after surgery. “I would not have been able to function without that support – for sleeping, for getting moving – the recovery pain was intense.” But Patterson realized that, “at some point, it was time to move on past that.”


Research suggests that most people recover fully by 12 months post-surgery. Errol says he made progress in that time, but that he made additional improvements since then. “It just takes time. The idea that recovery is going to happen overnight - that’s not the case.”

Message from NIH

On behalf of the National Institutes of Health, we thank you so much for your participation in the Acute to Chronic Pain Signatures (A2CPS) study. Our investment in this initiative reflects the high priority of this potentially transformative research effort on pain management care.

This important research effort would be impossible without individuals like you. Your participation in the A2CPS initiative will help us learn how to prevent chronic pain and how to better treat chronic pain after it develops. Your participation in the study can help ensure that the findings from the A2CPS initiative are applicable to all, regardless of age, gender, race or socioeconomic status. We hope that you will complete the study and we are grateful for the time and effort you put into it. As the A2CPS initiative progresses, we look forward to sharing updates with you and expressing our continued appreciation for your participation.

Chronic pain affects millions of Americans. Your commitment to the A2CPS initiative not only can help to reduce the burden of pain for individuals who need surgery but ultimately could help millions of others who suffer from or are at increased risk of developing chronic pain. Thank you!