Bilateral osteophytes are associated with more severe knee pain in women from an open population

Abstract

Purpose: Pain is a personal response that is influenced by several factors, for example genetic predisposition, experience and expectations, coping strategies, and sociocultural environment. Therefore, it is difficult to directly link structural osteoarthritis (OA) lesions to pain. Several studies showed that bone marrow lesions (BML) and effusion (inflammation) are associated with pain. Different types of pain have been distinguished within people with osteoarthritis (OA). With the modified painDetect questionnaire (mPD) nociceptive pain, mixed pain and neuropathic-like pain (or predominantly central sensitization) can be distinguished. Little is known about the association between the different types of pain and structural lesions seen on MRI. Therefore, our aim was to explore if there is a difference in structural lesions in the knee in women with different pain types. Methods: In the sub-cohort of 700 women of the Rotterdam Study measurements were performed, including a knee specific questionnaire and MRI of both knees. The knee specific questionnaire included the mPD for knee pain. All MRIs were scored with the MRI OA knee score (MOAKS). The knee was divided in patella and tibiofemoral region. Osteophytes were scored based on size. We defined the presence of a definite osteophytes as a score of 2 or higher. A cartilage lesion was defined as the presence of a cartilage lesion with a score of 1 or higher. Bone marrow lesions (BML) were defined as present if there was a score based on size of 1 or higher. Effusion was defined as present when there was more than a physical amount of fluid seen on the MRI. For each woman we defined if they had no, unilateral of bilateral lesions. The total score of the mPD was calculated and each woman was categorized as no pain (a score of 0), predominantly nociceptive pain (a score <12 on the mPD), mixed pain (a score between 12 and 18 on the mPD), or predominantly central sensitization (a score >18 on the mPD). The number and percentages of unilateral and bilateral osteophytes, cartilage lesions, BML and effusion were calculated. Univariate and multivariate generalized linear models were used to calculated the association between uni- or bilateral MRI features and the categories of the mPD. Results: Of the 700 women, 409 women (59.6%) had no knee pain, 231 women (33.7%) had predominantly nociceptive pain, 40 women (5.7%) had mixed pain, and only six women (0.9%) of this open population had predominantly central sensitization. Due to the low number of women with predominantly central sensitization, we summed the two highest categories of the mPD for further analysis. In table 1 the numbers and percentages of the MRI features are shown per group of women defined by their mPD score. No differences were seen for age per group, while a slightly increasing BMI was seen with each category of the mPD. Bilateral lesions were more likely seen in women with a higher score on the mPD. In table 2 the association between the presence of uni- and bilateral MRI features and the mPD score are shown. Due to high correlation between osteophytes in the patella and osteophytes in the TF joint (r=0.715), and between BML and cartilage lesions in the patella (r=0.664), we discarded the osteophytes and BMLs of the patella from the analysis. Multivariate analysis showed that the presence of osteophytes in the TF (unilateral (OR=1.80 (95%CI 1.1-3.0) p=0.026) and bilateral (OR=3.18 (95% CI 1.7-5.9) p<0.001)) were significantly associated to a higher score on the mPD, independent from age and BMI and the other MRI features. Bilateral effusion (OR=1.63 (95% CI 1.0-2.7) p=0.062) was borderline significantly associated with a higher score on the mPD. A higher BMI (1.055 (1.0-1.1) p=0.009) was also significantly associated to a higher score on the mPD. Conclusions: Women with more OA features seen on MRI, especially those with osteophytes in both knees, are more likely to have mixed pain and predominantly central sensitization (a higher score on the mPD) than women with less OA features. Furthermore, women with mixed pain and predominantly central sensitization had a higher BMI than women with predominantly nociceptive pain and women without pain. Further analysis will be needed to show if women with mixed pain and predominantly central sensitization also have more severe OA features seen on MRI, than women with predominantly nociceptive pain.View Large Image Figure ViewerDownload Hi-res image Download (PPT)