Results

Disease burden of osteoarthritis in China

In 1990, the number of OA cases in China was 4.6541 million, with a crude incidence rate of 395.61 per 100,000. The DALYs were 1.8294 million person-years, and the crude DALY rate was 155.50 per 100,000. By 2021, the number of OA cases had increased to 11.6527 million, with a crude incidence rate of 819.03 per 100,000. The DALYs reached 5.3274 million person-years, and the crude DALY rate was 374.44 per 100,000. From 1990 to 2019, the age-standardized incidence rate and standardized DALY rate showed an increasing trend, and the OA disease burden in China in 2021 was significantly higher than that in 1990 (Table 1, Fig. 1).

Indicator | China | Global
1990 | 2021 | 1990 | 2021
Female | Male | Total | Female | Male | Total | Female | Male | Total | Female | Male | Total
Number of cases (10,000) | 275.29 | 190.13 | 465.41 | 698.11 | 467.17 | 1165.27 | 1239.67 | 850.38 | 2090.05 | 2770.27 | 1892.95 | 4663.21
Crude incidence rate (/100,000) | 483.28 | 313.31 | 395.61 | 1004.99 | 641.62 | 819.03 | 468.18 | 316.63 | 391.86 | 704.55 | 478.09 | 590.93
Age-standardized incidence rate (/100,000) | 589.07 | 389.19 | 487.11 | 664.05 | 445.31 | 554.61 | 568.60 | 408.56 | 489.78 | 621.32 | 445.74 | 535.00
DALYs (10,000 person-years) | 109.72 | 73.23 | 182.94 | 323.25 | 209.49 | 532.74 | 548.52 | 343.37 | 891.89 | 1302.13 | 828.33 | 2130.46
Crude DALY rate (/100,000) | 192.61 | 120.67 | 155.50 | 465.35 | 287.71 | 374.44 | 207.15 | 127.85 | 167.22 | 331.16 | 209.21 | 269.97
Age-standardized DALY rate (/100,000) | 250.86 | 168.91 | 210.61 | 290.18 | 197.25 | 244.79 | 257.65 | 182.42 | 222.80 | 284.14 | 200.52 | 244.50

Fig. 1: Burden of Osteoarthritis in China and Globally, 1990 and 2021. (A) Age-standardized incidence rate (/100,000). (B) Age-standardized DALY rate (/100,000).

Global disease burden of osteoarthritis

In 1990, the global number of OA cases, DALYs, crude incidence rate, and crude DALY rate were 20.9005 million, 8.9189 million person-years, 391.86 per 100,000, and 167.22 per 100,000, respectively. By 2021, these indicators had risen to 46.6321 million, 21.3046 million person-years, 590.93 per 100,000, and 269.97 per 100,000. From 1990 to 2021, the standardized DALY rate and incidence rate of OA in China showed a significant upward trend: the standardized incidence rate in China was lower than the global level before 2003 but higher than the global level after 2003, while the standardized DALY rate in China was lower than the global level before 2021 (Table 1, Fig. 1).

OA disease burden by gender in China

From 1990 to 2021, the age-standardized incidence rate of OA in males increased from 389.19 per 100,000 to 445.31 per 100,000, and the standardized DALY rate increased from 168.91 per 100,000 to 197.25 per 100,000. In females, the standardized incidence rate rose from 589.07 per 100,000 to 664.05 per 100,000, and the standardized DALY rate increased from 250.86 per 100,000 to 290.18 per 100,000. The standardized incidence rate and DALY rate in females were higher than those in males in all years (Table 1, Fig. 2). Overall, the standardized incidence rate and DALY rate of OA showed an upward trend from 1990 to 2021, with AAPC values of 0.43% and 0.49%, respectively (both P < 0.001).

Fig. 2: Disease Burden of Osteoarthritis by Gender in China, 1990–2021. (A) Age-standardized incidence rate (/100,000). (B) Age-standardized DALY rate (/100,000).

For males, the AAPC of the standardized incidence rate was 0.42% (P < 0.001), showing an increasing trend over the entire period. By segment: it decreased from 1990 to 2000 (APC <0, P < 0.001), increased from 2000 to 2005 (APC = 2.40, P < 0.05), decreased from 2005 to 2010 (APC = −0.90, P < 0.05), and increased again from 2010 to 2021 (APC >0, P < 0.05). For females, the AAPC of the standardized incidence rate was 0.39% (P < 0.001), with a decreasing trend from 1990 to 2000 (APC <0, P < 0.05) and an increasing trend from 2000 to 2021 (APC >0, P < 0.05).

The AAPC of the standardized DALY rate in males was 0.51% (P < 0.001), showing an overall upward trend: increasing from 1990 to 1995 (APC = 0.26, P < 0.05), decreasing from 1995 to 2000 (APC = −0.19, P < 0.05), increasing from 2000 to 2005 (APC = 2.16, P < 0.05), and increasing again from 2010 to 2021 (APC >0, P < 0.05). In females, the AAPC of the standardized DALY rate was 0.47% (P < 0.001), with a decreasing trend from 1990 to 2000 (APC <0, P < 0.05) and an increasing trend from 2000 to 2021 (APC >0, P < 0.05) (Fig. 2, Table 2).

Indicator | AAPC (95% CI) | t-value | P-value
Age-standardized incidence rate
Male | 0.42 (0.36–0.48) | 13.6 | <0.001
Female | 0.39 (0.34–0.43) | 17.08 | <0.001
Total | 0.43 (0.39–0.46) | 24.28 | <0.001
Age-standardized DALY rate
Male | 0.51 (0.43–0.59) | 12.86 | <0.001
Female | 0.47 (0.42–0.52) | 18.84 | <0.001
Total | 0.49 (0.46–0.52) | 31.54 | <0.001

OA disease burden by age in China

The incidence rate of OA increased with age: it remained low in populations under 39 years old, began to increase slowly in those aged 40–54, reached the highest the 55–59 age group, and remained stable in those aged 55–85 and above. The DALY rate of OA was mainly concentrated in people over 55 years old, with the highest DALY rate in the age group over 85 years old.

From 1990 to 2004, the age-specific incidence rate and DALY rate of OA remained stable across all age groups; after 2004, these indicators began to gradually increase (Fig. 3).

Fig. 3: Disease Burden of Osteoarthritis by Age Group in China, 1990–2021. (A) Incidence rate (/100,000). (B) DALY rate (/100,000).

Disease burden of OA subtypes in China

In the GBD 2021 database, OA subtypes mainly include hand osteoarthritis, hip osteoarthritis, knee osteoarthritis, and other osteoarthritis. From 1990 to 2021, the standardized incidence rate and DALY rate of knee osteoarthritis were significantly higher than those of other subtypes, while hip osteoarthritis had the lowest standardized incidence rate and DALY rate. In 2021, the standardized incidence rate and standardized DALY rate of knee osteoarthritis were 406.42 per 100,000 and 162.44 per 100,000, respectively; for hand osteoarthritis, the rates were 92.70 per 100,000 and 51.26 per 100,000; for hip osteoarthritis, the rates were 0.62 per 100,000 and 13.86 per 100,000; and for other osteoarthritis, the rates were 41.63 per 100,000 and 22.75 per 100,000. Compared with 1990, all burden indicators of OA subtypes in China increased in 2021 (Fig. 4).

Fig. 4: Disease Burden of Osteoarthritis Subtypes in China, 1990–2021. (A) Age-standardized incidence rate (/100,000). (B) Age-standardized DALY rate (/100,000).

Interpretation of Hip OA Data: It is important to note that the exceptionally low recorded incidence rate of hip OA may not fully reflect the true epidemiological burden. We tentatively put forward a hypothesis that this anomaly may stem from significant underdiagnosis in primary care settings and limited access to diagnostic imaging (e.g., X-ray, MRI) in resource-constrained regions of China. Unlike knee OA, which presents with more obvious symptoms, hip OA is often misdiagnosed or overlooked in the early stages. However, this explanation remains speculative without supporting clinical registry or imaging prevalence data from Chinese populations, and should not be regarded as a definite conclusion; the reported incidence may only represent the ‘tip of the iceberg’ of the actual disease burden.

Model construction and projection

Comprehensive model fitting indicators, residual diagnostic test results, cross-validation performance, and 95% forecast uncertainty intervals for 2044 are summarized in Table 3 to fully demonstrate model robustness. Ljung-Box test results showed no significant residual autocorrelation for both prediction models, and ten-fold cross-validation yielded low MAPE values, indicating no overfitting and reliable long-term extrapolation performance.

Outcome indicator | Prediction model | R2 | Ljung-box P-value | 10-Fold cross-validation MAPE (%) | 2044 predicted value (per 100,000) | 95% prediction interval (per 100,000)
Age-standardized DALY rate | ARIMA (0,2,1) | 0.999 | 0.723 | 1.21 | 292.02 | (278.15, 306.79)
Age-standardized incidence rate | Brown exponential smoothing | 0.997 | 0.681 | 1.56 | 589.00 | (572.36, 608.42)

Using the age-standardized incidence rate and DALY rate of OA from 1990 to 2021 as raw data, the optimal model for the standardized DALY rate was determined to be ARIMA (0, 2, 1) with an R2 of 0.999. The model projection showed that the standardized DALY rate of OA in China would continue to rise from 246.27 per 100,000 in 2022 to 292.02 per 100,000 in 2044. For the standardized incidence rate, the Brown model was selected with an R2 of 0.997, indicating an excellent fit to the historical trend. The projection indicated a steady upward trend, increasing from 556.11 per 100,000 in 2022 to 589.00 per 100,000 in 2044 (Fig. 5).

Fig. 5: Projection of Osteoarthritis Disease Burden in China, 2025–2044. (A) The model of age-standardized incidence rate (/100,000). (B) The model of age-standardized DALY rate (/100,000).

Uncertainty Consideration: Table 3 lists the 95% prediction intervals of all 2044 forecast indicators, with relatively wide interval ranges reflecting prominent statistical uncertainty for 20-year long-term extrapolation. While this study provides point estimates for future trends and the high R2 values (0.999 and 0.997) indicate good fitting for historical patterns, our univariate forecasting framework only relies on past OA burden data and cannot integrate dynamic future changes in population obesity levels, residents’ physical activity status and national healthcare policies. These key modifiable drivers may substantially alter actual OA trends and generate deviations between real-world burden and our predicted values, so all projection results must be interpreted prudently.