When someone comes into our office with a swollen knee, they will often discuss with us the problems of their knee pain with the thought that the inflammation is the cause of that pain. That is why, they often tell us, they are on anti-inflammatories, “to help the pain.” Therefore, before they come visit us, they have associated anti-inflammatories with reduction in knee pain. The question then is does knee inflammation really cause knee pain?
An April 2022 paper (1) reviewed the current medical literature on the relationship between inflammatory markers and pain in patients with knee osteoarthritis. Inflammatory markers were listed as effusion, synovitis, baker’s cysts, cytokines and C-reactive protein. The researchers found that the strength of the association between inflammation and pain does not exceed the moderate level. Meaning a clear cut association between inflammation and pain could not be made. In fact the evidence was conflicting.
That knee swelling or inflammation causes knee pain is the subject of debate in the medical community. In a paper for m2011, doctors demonstrated the problems of what an MRI says is going on in the knee, how much swelling is going on in the knee, and then trying to determine if what the doctors were seeing was actually causing the knee pain.
In this 2011 paper (2) doctors systematically evaluates the association between MRI findings (cartilage defects, bone marrow lesions, osteophytes (bone spurs), meniscal lesion, effusion/synovitis, ligamentous (knee ligament) abnormalities, subchondral cysts and bone attrition) and pain in patients with knee osteoarthritis in order to establish the relevance of such findings when assessing an individual patient.
The doctors here found that bone marrow lesions and having pain when inflammation was present may indicate the source of the knee pain, however, while this evidence was moderate, other MRI findings were limited or conflicting. A strong recommendation connecting inflammation and pain could not be made.
Why use this 2011 as a benchmark to reviewing other research? Certainly things have changed for the better since 2011? No, not really. This is attested by the number of research papers using this research as a citation. Over 100.
1 Dainese P, Wyngaert KV, De Mits S, Wittoek R, Van Ginckel A, Calders P. Association between knee inflammation and knee pain in patients with knee osteoarthritis: a systematic review. Osteoarthritis and Cartilage. 2021 Dec 27.
2 Yusuf E, Kortekaas MC, Watt I, Huizinga TW, Kloppenburg M. Do knee abnormalities visualised on MRI explain knee pain in knee osteoarthritis? A systematic review. Annals of the rheumatic diseases. 2011 Jan 1;70(1):60-7.