People who suffer from depression or anxiety before joint replacement surgery tend to feel more pain afterwards, according to a new study.
People who catastrophised ahead of the same surgery also reported more pain.
In the UK, about 9 million people aged 45 or older have reported to their doctor with knee or hip pain, due to osteoarthritis, with numbers expected to rise as the population ages.
Of those who go ahead with a knee or hip replacement, a third develop greater pain and disability after surgery.
The study, led by Dr Nils Niederstrasser, at the University of Portsmouth, analysed a wide cross section of existing research and is published in the Journal of Pain.
He said: “Chronic joint pain is exceedingly common with roughly one in every five people in the UK who are 45 or older having sought treatment for knee osteoarthritis alone.
“We’ve found even modest depression, anxiety and catastrophising are robust predictors of whether a patient later experiences improvements in terms of pain relief and ability to move the joint.
“That’s what’s fascinating – all participants included in the study had undergone successful surgery, no subsequent fixing or repairs were required.
“It has long been understood that a patient’s mental wellbeing has an effect on their outcome after surgery, but we would go further and argue that someone’s mental state is a useful predictor of how someone will fare post-operation.
“This should be considered more prominently in treatments and care before and after this type of surgery.”
Why people suffering depression or anxiety or who are catastrophising suffer most post-operation might be due to having a fear of pain, being more sensitive to pain, or having a low mood, which often means a person remains sedentary.
Dr Niederstrasser said: “The worst thing you can do after surgery is to sit on the couch and wait for things to heal and get better by themselves. You need to get up and move once it is safe to do so, which includes engaging in exercises and activities.
“Anyone who has ever had surgery or had to go through some form of physical rehabilitation knows that pain is inevitable. So, if you are afraid of pain, or in your mind, pain is linked with catastrophe, or if your mood is low and you can’t bear the thought of having to suffer through rehabilitation exercises or even the pain that you will experience when you stand up, then you are less likely to engage in any such activity.
“In essence, you avoid movement and activity, such as rehabilitation exercises, for fear of experiencing pain and this inactivity is what can make the pain worse and hamper the healing process.”
Scientists are also aware that depression, anxiety or catastrophising might be linked to a greater sensitivity to pain.
Dr Niederstrasser said it might be that repeated pain, as expected after surgery, leads to sensitisation whereby the nervous systems reacts more strongly to pain-related signals, which can amplify the pain experience and put a person off trying to move.
“Pain is the ultimate punishment if you think about it in conditioning terms,” he said. “We encourage behaviour by removing pain and the best way to deter someone from doing something is to pair it with pain. That’s why we don’t run a marathon with a broken leg and touch the hot stove only once.
“This sensitisation and the subsequent increased pain response may also mean that medication that would normally lead to adequate pain relief may not be potent enough anymore (because the pain is greater) and so a higher dose is needed.”
Dr Niederstrasser and his co-author, Dr Stephanie Cook, at De Montfort University, carried out an extensive review of studies linking patients’ mental state and their surgical outcomes, focusing on how well patients fared after a hip or knee replacement, including how much pain relief they asked for, how well their new joint functioned, their mood and quality of life.
They wanted to examine if any previous studies in this field showed bias or were selective in their reporting. Instead they found a strong and consistent link between pre-surgery mental state and post-surgery outcomes.
Dr Niederstrasser said: “Depression and anxiety might stop someone from doing rehab exercises or resume their normal daily activities. To compound the problem, by remaining inactive, they also are at greater risk of arthritis and further loss of function, leading inevitably to poorer health and mood.”
Factors such as fear, catastrophising and depression need to be targeted when providing pre- and after-care for patients. This is currently not done routinely.