My patient came in yesterday saying that his knee started clicking even though he didn't feel any pain with the clicking. There were occasional twinges of pain only occasionally. However, he was worried that his knee will get worse. After assessing his knee (which turned out fine) and reassuring him, I told him my own experiences.
After I had my third knee operation (within the space of a year), my right knee started feeling better. Of course I started training again as soon as the surgeon permitted. For a start, I ran almost exclusively on grass (since it was the softest surface I could find), often going multiple rounds, to ensure that I can get my mileage since I was hoping to compete again after my injuries.
However, I was much more sensitive about my right knee, to the point of being paranoid about every sensation I felt in the knee. Each time I was on the bus or MRT and if someone came close to my right knee, I'd move away and glare at the person for coming too close to me. Does this sound like you?
Well, it turns out this action of pain sensitization is common across other painful knee disorders as well. In patients with knee osteoarthritis, pressure from placing your hands on the knees alone can trigger pain. The good news is that this sensitization for painful knees can be treated.
The following systematic review investigated 52 studies that studied pain sensitization across four different painful knee disorders. The authors found evidence of pain sensitization in people with knee osteoarthritis, patellofemoral pain and post meniscectomy patients. They however found conflicting evidence in patients with patella tendinopathy.
The researchers found that the extent of structural joint damage in the observed knee disorders does not correlate to the severity of symptoms. Hence, pain is not necessarily a 'signal' from a joint or area that is damaged. Meaning x-rays or MRI results does not correlate with pain. Some patients have no 'damage' on x-ray/ MRI but have a lot of pain, while others with lots of damage on film may have no pain.
Many factors play a role to determine if a person will perceive a stimulus as painful or not since pain can be a complex experience that is associated with memories, belief and social context. Anxiety, depression, fear of movement, viewing their condition considerably worse than it actually is may also play a part.
It is suggested that repetitive stimulation may lead to subsequent sensitization of the nervous system. This include loading of the knee joint, ongoing inflammation at the knee joint or related tissues and altered biochemical markers. These factors contribute and maintain the pain sensitization in the knees.
In patients with knee osteoarthritis and patellofemoral joint pain, pain sensitization can be treated through exercise therapy, mobilization, pharmacological (yes, painkillers) and surgical intervention. Correct exercise is recommended for treatment of painful knees. There is the incorrect belief that exercise may harm the joint cartilage in patients with osteoarthritis.
If doctors, surgeons and physiotherapists focus less on x-rays/ MRI's and more on factors (including psychosocial factors mentioned above) relating to each patient's pain and disability, there will be more opportunities for collaboration and improved treatment outcomes.
Reference
De Oliveira Silva D, Rathleff MS, Petersen K et al (2019). Manifestations Of Pain Sensitization Across Different Painful Knee Disorders: A Systematic Review Including Meta-analysis And Metaregression. Pain Med. 20(2): 335-358. DOI: 10.1093/pm/pny177.
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