The aim of this study was to evaluate the relationship between radiological severity by the grades of the Kellgren-Lawrence scale independently and divided into two groups: “0 and 1” and “2 to 4”, characterizing a “without” group and a group “with” radiological KOA and instruments that assess depressive symptoms, cognitive loss, risk of falling and specific quality of life for osteoarthritis in elderly individuals. This investigation stands out for independently evaluate the radiological grades of KOA by K&L scale, once the most common in the literature is the comparison of them in grouped grades, establishing or not the presence of radiological KOA. When assessed independently, the grades of the K&L scale are not related to depressive symptoms, cognitive loss, pain, stiffness, functional difficulty and risk of falling.
When assessing the presence or not of KOA (groups 2 to 4 and 0 and 1) in the tests related to mental health (GDS, MMSE) the groups evaluated obtained similar ratings, showing no significant differences between individuals with or without KOA. However, we should consider that most of the selected sample was classified in the GDS and MMSE tests with the presence of depressive symptoms and mild cognitive loss and being a cross-sectional study we cannot say that there is no relationship between the K&L scale and these questionnaires.
Regarding to the presence of depressive symptoms and the K&L scale, Kim et al. (9) observed that elderly people with symptomatic KOA (WOMAC > 39), had significantly higher scores in the GDS than those without symptoms and concluded that the presence of depressive symptoms is associated with an increased risk of having symptomatic OA, however this was only observed in the elderly with K&L grades from 0 to 3, but not with grade 4. Although this study suggests that there is a relationship between the GDS and the grades of K&L evaluated groups determined by the presence of symptomatic OA, differing from the type of analysis investigated here, which refers to the presence of depressive symptoms and their relationship with the severity of radiological OA.
For El Monaem et al. (10), the radiological classification of K&L is correlated with the emergence of depression in individuals with KOA assessed by the Beck depression inventory (BDI), indicating different results from ours in relation to depressive symptoms and radiological severity. This might be explained to used a diferent questionnaire, suggesting that there may be differences between them (GDS and BDI) and according to the findings to Bentz and Hall (29) GDS has more ability to correctly depression diagnosis than the BDI.
Regarding to cognitive losses and their association to K&L grades, divergences were found in relation to the results presented. The study by Yoshimura et al. (14) points to significantly lower MMSE score in individuals with radiological KOA (grade ≥ 2) than those without (grade 0 and 1). In addition, the incidence of radiological OA decreases as the MMSE score increases, that is, once the individual performs better in relation to cognitive impairment. Similarly, the presence of cognitive losses were associated with a five times greater risk of incidence of radiological OA in individuals without the disease. However, there were no significant associations between the presence of cognitive impairment, MMSE score and knee OA progression, corroborating our results.
In addition, when comparing groups, we found that the risk of falling from high and moderate levels in BBS was more frequent in individuals with radiological OA than in individuals without. In addition, as well in the WOMAC as in BBS tests mean values were found that keep the groups in the same classification level, that is, in the WOMAC both groups are in the “Little” category and in the BBS in the “no risk” category.
Despite the groups belonging to the same level of classification, the difference in the mean between them points out to group “2 to 4” as worse than the group “0 and 1”, as it presents significantly higher values in WOMAC and lower values in BBS. In this sense, it is understood that even in good health regarding the level of pain, stiffness, functional difficulty and risk of falling, the elderly with radiological OA (grades 2 to 4) are more debilitated than those without OA (grades 0 and 1).
Kim et al. (13) indicated that patients with moderate and severe knee OA (grades 3 and 4) have worse functional performance in BBS than those considered to have mild OA (grade 2 or less), approaching our results. On the other hand, it is documented that individuals with a worse K&L classification also performed worse on the TUG (12, 13), which was not observed in our study. In the present study, the groups evaluated had similar performance in the TUG test, but unlike BBS, they did not show significant differences. Thus, it is shown that the TUG test and the K&L classification for knee OA when evaluated between groups are not related, which was previously observed in relation to the hip joint (19).
The divergence between the results of these instruments that assess the risk of falling can be justified by the sample evaluated, which was poorly classified in the high and moderate risk levels in the TUG and also due to BBS measures of static and dynamic balance in several tasks, while the TUG measures mobility (gait) and balance solely by a single task. Therefore, the complexity given by the “increasing difficulty” component and the number of tasks to be performed in BBS may have influenced the test difficulty for elderly people with KOA. However, it was expected that this population would have difficulty in the movements of sitting, standing and walking, due to the presence of osteophytes and the reduction of the joint space, to be morphological alterations that hinder the joint functionality.
Li et al. (12) points to the WOMAC as related to the radiological grade. A significant worsening in its score, as well as in the visual analog pain scale (VAS), is suggested by individuals with knee OA in grades 3 and 4, when compared to individuals with grades 0 to 2. These data are also similar to our findings.
According to Lethbridge-Cejku et al. (30), radiological changes resulting from knee osteoarthritis are significantly associated with the presence of pain. People with grades 3 and 4 have a higher proportion of recurrent pain than people with lower grades and there is a significant increase in this proportion of constant pain with punctuated changes in K&L scale, such as increased osteophyte size, greater narrowing of the joint space and presence of subchondral sclerosis. This result may justify the reason why an instrument that measures pain, such as WOMAC, is related to image examination. In addition, for Pereira et al. (31) the proportion of individuals who report higher levels of pain (measured by a specific questionnaire and referring to pain experienced in the last six months) is higher among those who are classified in grades ≥ 2 by the K&L scale.
On the other hand, for Creamer et al. (15) these joint changes and the functional difficulty measured by WOMAC are not correlated. However, for Szebenyi et al. (11) the probability of individuals with KOA to present pain or reduced function, assessed by WOMAC and VAS is greater if these changes occur in the tibiofemoral (medial and / or lateral) and patellofemoral compartments at the same time and not in only one of them, which was not evaluated by Creamer et al. (15). Furthermore, pain was more associated with subchondral bone sclerosis than with other changes in knee OA (11), the presence of subchondral lesions generates mechanical pain and is related to body weight support (32, 33) however for Ciccuttini et al. (34) the greatest association of pain is with the development of osteophytes (16). In this sense, it seems that the type of change identified by the K&L scale is more efficient in predicting pain and functional reduction than the grade score itself.
Unlike our findings, for Kumar et al. (19) the radiological classification, determined by the K&L scale and divided into the group with OA (grades 2 and 3) and without OA (grades 0 and 1), is not related to pain or function. However, these were measured for the hip joint, using the outcome assessment instrument for hip deficiency and osteoarthritis (HOOS), which also indicated the non-association between the radiograph and the other dimensions assessed (symptoms, activities of daily living and quality of life related to the hip joint). Thus, the different results can be explained by different assessment methods and a different joint.
On the correlation analysis between the grades of the K&L scale and the numerical variables, the results indicated the WOMAC as significant when avalue the total sample. This result reveals the worsening of pain, stiffness and functional difficulty as the radiological grade increases. Corroborating the findings of Szebenyi et al. (11), who also found as a result the correlation between pain and function with the classification of the K&L scale for KOA. The VAS and WOMAC scores functioned as a subscale of the K&L scale in all grades (0 to 4). For Kim et al. (9) there is a significant correlation between the K&L classification, and the total score and all subscales of the WOMAC. In their study, 660 elderly people were investigated and they found that those with symptomatic KOA, classified by the WOMAC score > 39, obtained higher scores on the K&L scale than those without symptons. Furthermore, as the radiological grades increased, the frequency of symptomatic OA became more prevalent.
On the other hand, other studies suggest that the WOMAC score and the radiological grades by the K&L are not correlated (16, 18). Unlike our study, they had most of their sample classified in grade 3. Still in our results, as presented in other studies, when comparing the three WOMAC domains between grades, the groups evaluated and the total sample, there were no significant differences or correlations (18, 35).
This study is a pioneer in the comparison between the independent degrees of the K&L scale and factors associated with KOA, such as depressive symptoms, cognitive loss, quality of life related to OA and risk of falling in elderly Brazilians. In addition, it assesses several factors associated with KOA in the same investigation. As limitations, this study presents a cohort selected for convenience, cross-sectional analysis and did not have all the instruments for assessing symptoms correlated with the topic in the literature for possible comparisons.
Further studies are suggested to better understand the relationship between the presence of depressive symptoms and cognitive loss and the radiological classification determined by the K&L scale. In addition, studies that understand the relationship between radiological severity and the risk of falling, measured by different instruments.