Title: Adults at risk for accelerated knee osteoarthritis report different patterns of knee symptoms than those at risk for common knee osteoarthritis: data from the osteoarthritis initiative
Abstract: Purpose: Accelerated knee osteoarthritis (KOA) may be a unique subset of KOA where a knee progresses from normal appearance to advance-stage disease within 4 years. Individuals with accelerated KOA report greater symptoms (i.e., pain, dysfunction, and other symptoms) than those with common KOA, especially the year before they develop radiographic evidence of accelerated or common KOA. It is unclear if adults who develop accelerated KOA experience symptoms differently than those who develop common KOA. Hence, we examined if adults who develop accelerated KOA had greater knee symptoms with certain activities than those with or without common KOA and if the pattern of symptoms differed between those with accelerated or common KOA. Methods: We conducted a case-control study using data from baseline and the first 4 annual visits of the Osteoarthritis Initiative. Participants had no radiographic KOA at baseline (Kellgren-Lawrence [KL] < 2). We classified 3 groups: 1) accelerated KOA: ≥1 knee developed advance-stage KOA (KL = 3 or 4) within 48 months, 2) common KOA: ≥1 knee increased in radiographic scoring (excluding those with accelerated KOA), and 3) No KOA: no change in KL grade by 48-months. Blinded readers recorded KL grades based on weight-bearing, fixed-flexion posterior-anterior knee radiographs that were obtained at baseline and follow up visits. For symptoms (i.e., pain, dysfunction with certain activities, and other symptoms) we focused on individual items from the WOMAC pain/function subscales and KOOS pain/symptoms subscales collected at an index visit for each person. The index visit for accelerated and common KOA was defined as the visit a year before the person met the definition for accelerated or common KOA. For those with no KOA, the index visit was defined as the second to last visit (36 months). To examine difference in knee symptoms among the 3 groups (predictors) we used 3 ordinal logistic regression models for each symptom (3- or 4-level outcome, see Table 1). To study the pattern of symptoms we performed 2 factor analyses (one among those with accelerated KOA and another among those with common KOA). Factors with an Eigenvalue > 1 were retained. Results: Individuals who develop accelerated or common KOA within the next 12 months reported greater symptoms in most activities than those with no KOA (Table 1), as well as greater swelling and symptoms with knee bending (data not shown). Those who developed accelerated KOA were 2 to 2.5 times more likely to report greater difficulty with lying down, pain with straightening the knee, and pain walking compared with adults who developed common KOA. Among those who developed accelerated KOA, the factor that accounted for most of the variance in symptoms within the group reflected a difficulty with a wide range of activities of daily living while the corresponding factor in common KOA emphasized pain and difficulty with walking and standing (Table 2). A factor among those who developed accelerated KOA but not in those with common KOA was symptoms with bending and straightening the knee. Conclusions: Symptoms are common in the year prior to the development of accelerated or common KOA. There are 4 factors of pre-diagnosis pain patterns that are similar in those that develop accelerated and common KOA. Individuals who develop accelerated KOA report difficulty with many activities of daily living, especially activities with frequent knee bending, while those who develop common KOA report symptoms primarily with walking and standing. Those who develop accelerated KOA uniquely have symptoms with straightening or bending the knee. Future study of these factors with MRI findings may help to identify early sources of pain that can potentially be the focus of therapeutic targets. Our results may also help identify individuals at risk for accelerated KOA or with early-stage accelerated KOA.Table 1Adults at Risk for Accelerated Knee Osteoarthritis (KOA) Are More Likely to Report Greater Knee SymptomsNo KOACommon KOAAccelerated KOA (AKOA)VariableNone (score = 0)Mild (score = 1)Moderate-Extreme(score = 2 to 4)None(score = 0)Mild (score = 1)Moderate-Extreme(score = 2 to 4)None (score = 0)Mild (score = 1)Moderate-Extreme(score = 2 to 4)AKOA vs No KOA OR (95% Cl)KOA vs No KOA OR (95% Cl)AKOA vs KOA OR (95% Cl)Difficulty: down stairs964 (74%)240 (18%)101 (8%)114 (61%)52 (28%)20 (11%)27 (51%)13 (25%)13 (25%)3.02 (1.79, 5.09)1.73 (1.26, 2.37)1.77(0.99, 3.18)Difficulty: up stairs904 (69%)267 (20%)134 (10%)104 (56%)53 (15%)29 (16%)26 (49%)16 (30%)11 (21%)2.32 (1.38, 3.92)1.74(1.29, 2.36)1.34(0.75, 2.40)Difficulty, stand from sitting930 (71%)262 (20%)116 (9%)107 (57%)45 (24%)35 (19%)26 (48%)16 (30%)12 (22%)2.73 (1.63, 4.57)1.94(1.44, 2.63)1.38 (0.78, 2.45)Difficulty: standing1121 (86%)142 (11%)46 (4%)142 (76%)31 (17%)14 (7%)37 (69%)13 (34%)4 (7%)2.68 (1.49, 4.83)1.91 (1.33, 2.76)1.39 (0.72, 2.69)Difficulty: bending856 (67%)254 (20%)162 (13%)94 (53%)46 (26%)37 (21%)27 (53%)11 (22%)13 (25%)1.97 (1.16, 3.36)1.82 (1.34, 2.46)1.09 (0.60, 1.97)Difficulty: walking1131 (86%)138 (11%)39 (3%)147 (79%)32 (17%)8 (4%)39 (72%)12 (22%)3 (6%)2.41 (1.31, 4.45)1. 72 (1.18, 2.53)1.41 (0.71, 2.79)Difficulty: in car/out of car972 (74%)232 (18%)102 (8%)112 (60%)52 (28%)23 (12%)31 (57%)13 (24%)10 (19%)2.27 (1.33, 3.86)1.90 (1.39, 2.59)1.20 (0.67, 2.17)Difficulty: shopping1122 (87%)119 (9%)54 (4%)143 (77%)30 (16%)13 (7%)38 (73%)12 (23%)2 (4%)2.23 (1.18, 4.22)1.93 (1.33, 2.81)1.16 (0.57, 2.33)Difficulty: socks on1115 (85%)131 (10%)63 (5%)154 (82%)23 (12%)10 (5%)43 (80%)6 (11%)5 (9%)1.51 (0.77, 2.96)1.22 (0.82, 1.84)1.24 (0.58, 2.63)Difficulty: get out of bed1067 (82%)162 (12%)79 (6%)133 (72%)37 (20%)16 (9%)35 (65%)9 (17%)10 (19%)2.59 (1.49, 4.53)1.73 (1.23, 2.44)1.51 (0.81, 2.81)Difficulty socks off1138 (87%)114 (9%)57 (4%)154 (82%)77 (14%)6 (3%)44 (81%)7 (13%)3 (6%)1.50 (0.74, 3.03)1.38(0.92, 2.08)1.09 (0.50, 7.37)Difficulty: lying down1174 (90%)94 (7%)41 (3%)157 (84%)23 (12%)7 (4%)39 (72%)9 (17%)6 (11%)3.40 (1.84. 6.28)1.64(1.07, 2.52)2.10(1.04, 4.25)Difficulty: sitting1147 (88%)122 (9%)39 (3%)147 (79%)32 (17%)8 (4%)43 (80%)8 (15%)3 (6%)1.83 (0.93, 3.60)1.91 (1.30, 2.81)0.96 (0.46, 2.02)Difficulty: on/off toilet1098 (84%)153 (12%)57 (4%)145 (78%)31 (17%)11 (6%)39 (72%)10 (19%)5(9%)2.03 (1.11, 3.73)1.51 (1.04, 2.18)1.36 (0.69. 2.67)Difficulty: heavy chores962 (77%)179 (14%)104 (8%)121 (70%)35 (20%)17 (10%)32 (62%)11 (21%)9 (17%)2.16 (1.24, 3.77)1.42 (1.01, 2–02)1.53 (0.82, 2.87)Difficulty: light chores1129 (86%)143 (11%)34 (3%)149 (81%)31 (17%)5 (3%)43 (80%)7 (13%)4 (7%)1.70 (0.87, 3.32)1.52 (1.02, 2.26)1.12 (0.53, 2.36)Pain: straightening knee fully1100 (84%)151 (12%)57 (4%)143 (76%)34 (18%)10 (5%)34 (63%)12 (22%)8 (15%)3.22 (1.85, 5.62)1.60 (1.11, 2.31)2.04 (1.08, 3.85)Pain: bending knee fully962 (74%)235 (18%)110 (8%)121(65%)42 (23%)23 (12%)29 (54%)12 (22%)13 (24%)2.66 (1.58, 4.48)1.50 (1.09, 2.07)1.75 (0.97, 3.15)Pain: walking1013 (77%)222 (17%)74 (6%)127 (68%)47 (25%)13 (7%)27 (50%)14 (26%)13 (24%)3.88 (2.31, 6.51)1.58 (1.13, 2.19)2.49 (1.38, 4.84)Pain: up/down stairs775 (59%)342 (26%)190 (15%)86 (46%)60 (32%)40 (22%)22 (42%)12 (23%)19 (36%)2.53 (1.52, 4.20)1.67 (1.25, 2.23)1.51 (0.86, 2.66)Pain: in bed1152 (88%)99 (8%)58 (4%)147 (79%l26 (14%)14 (7%)43 (80%)6 (11%)5 (9%)1.91 (0.97. 3.75)1.98(1.34, 2.91)0.97(0.46, 2.03)Pain: sit or lie down1111 (85%)152 (12%)45 (3%)144 (77%)31 (17%)12 (6%)35 (65%)13 (24%)6 (11%)3.12 (1.77, 5.50)1.70 (1.17, 2.46)1.87 (0.96, 3.46)Pain: standing1038 (79%)203 (16%)66 (5%)129 (69%)47 (25%)11 (6%)32(59%)13 (24%)9 (17%)2.84 (1.65, 4.87)1.68 (1.20, 2.35)1.72 (0.94, 3.15)Difficulty with tub and pain with twisting was omitted from the analyses b/c > 20% was missing.All variables had statistically significant chi square p-values with the exception of difficulty taking socks on/off Open table in a new tab Table 2Factor Analysis Identified Novel Groups of Common Symptoms among Those at Risk for Accelerated Knee Osteoarthritis (AKOA) and Common Knee Osteoarthritis (KOA)AKOA (n = 46 out of 54)KOA (n = 162 out of 187)Factor1Factor2Factor3Factor4Factor5Factor1Factor2Factor3Factor4Difficulty: up stairs0.860.170.070.230.000.310.680.250.15Difficulty: down stairs0.860.080.120.110.080.160.730.210.22Difficulty: standing0.480.660.140.110.140.690.410.210.17Difficulty: bending0.680.330.220.190.190.440.660.160.21Difficulty: walking0.380.600.430.340.080.730.300.200.17Difficulty: in car/out of car0.720.250.200.38−0.060.170.610.230.21Difficulty: shopping0.360.400.210.460.130.450.500.330.23Difficulty: socks on0.200.180.120.880.190.250.250.860.17Difficulty: get out of bed0.660.100.390.420.140.270.400.520.20Difficulty: socks off0.280.020.090.820.320.240.250.870.17Difficulty: lying down0.100.210.860.13−0.010.190.220.290.74Difficulty: sitting0.180.790.410.120.010.220.490.190.25Difficulty: on/off toilet0.750.120.280.050.170.250.530.380.10Difficulty: heavy chores0.360.470.080.130.150.440.560.360.11Difficulty: light chores0.280.430.290.160.010.500.440.360.12Pain: straightening knee fully0.440.320.350.290.140.440.220.270.27Pain: bending knee fully0.420.330.230.180.050.630.230.280.16Symptoms: swelling0.200.070.350.24−0.010.300.110.090.26Symptoms: crepitus0.320.070.14−0.010.230.020.070.010.03Symptoms: catching−0.010.050.00−0.030.170.010.180.020.07Symptoms: straightening0.050.090.040.210.790.050.08−0.090.09Symptoms: bending0.140.010.080.240.810.210.160.100.01Pain: walking0.370.420.110.37−0.050.620.130.140.26Pain: up/down stairs0.710.260.010.150.060.420.430.200.18Pain: in bed0.260.140.830.120.130.260.260.100.80Pain: sit or lie down0.180.510.66−0.020.060.270.110.190.56Pain: standing0.660.290.230.090.130.660.130.150.16Eigen Value13.442.051.771.531.3412.761.471.121.09Variance explained by each factor6.023.143.142.741.744.224.172.972.26 Open table in a new tab Difficulty with tub and pain with twisting was omitted from the analyses b/c > 20% was missing. All variables had statistically significant chi square p-values with the exception of difficulty taking socks on/off