Association of Knee and Hip OA with Fall Risk and Fractures

By Youyou Zhang, Xiaoxi Li, Yining Wang, Liru Ge, Faming Pan, Tania Winzenberg, and Guoqi Cai

Patients with knee and hip OA frequently have pain, muscle weakness, impaired joint proprioception, and poor balance, which are important risk factors for falls. 

Falls and osteoarthritis (OA) are major public health problems. The incidence of falls and fractures increases with age, and knee OA and hip OA are also highly prevalent in older populations. Nearly 30% of individuals older than 45 years have radiographic evidence of knee OA, and about half have knee symptoms. Patients with knee and hip OA frequently have pain, muscle weakness, impaired joint proprioception, and poor balance, which are important risk factors for falls. Studies evaluating the association of knee and hip OA with falls and fractures have inconsistent findings. The aim of this systematic review and meta-analysis was to investigate associations of symptomatic and radiographic knee and hip OA with risk of falls, recurrent falls, and fractures.

Methods

An electronic search of databases from inception to February 2023 was conducted. Two authors independently screened studies, extracted data, and assessed the risk of bias using the Newcastle-Ottawa Scale tool in eligible studies. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using random-effects models.

Results

Of 17 studies included (n = 862,849), 2 had a high risk of bias. Among studies that evaluated falls or fractures as outcomes, 7/8 (87.5%) and 5/11 (45.5%) were self-reported, respectively. Both symptomatic knee and hip OA were associated with increased risk of recurrent falls (knee: OR = 1.55, 95% CI 1.10 to 2.18; hip: OR = 1.50, 95% CI 1.28 to 1.75) but not falls or fractures. Radiographic knee OA increased risk of falls (OR = 1.28, 95% CI 1.03 to 1.59) but did not significantly increase risk of recurrent falls (OR = 1.39, 95% CI 0.97 to 1.97) or fractures (OR = 1.22, 95% CI 0.99 to 1.52). Radiographic hip OA decreased the risk of recurrent falls (OR = 0.70, 95% CI 0.51 to 0.96) but had no statistically significant association with fractures (OR = 1.16, 95% CI 0.79 to 1.71).

Discussion

The results of this meta-analysis revealed that symptomatic knee and hip OA were associated with an increased risk of recurrent falls, but were not associated with the risk of fractures. Radiographic knee OA was associated with an increased risk of falls. While the quality of evidence of included studies was moderate to very low, symptomatic knee and hip OA should be considered as potential risk factors for falls and falls risk assessment, and preventive interventions in people with OA at these sites considered.

While only radiographic knee OA was associated with an increased risk of falls, both symptomatic and radiographic knee OA showed a similar magnitude in the increased risk of recurrent falls, though for radiographic knee OA this was not statistically significant. This is likely to reflect a real effect of knee OA on falls because a single fall may be coincidental, whereas recurrent falls are more likely to have an internal, disease-related cause, and they generally lead to more serious consequences. Considering the high prevalence of knee OA and the severity of falls in older adults, it is important to strengthen medical care and develop preventive interventions to reduce falls in this population. In patients with knee and hip OA, routine use of screening tools may help to identify those at increased risks of falls and fractures, and this is likely to promote the implementation of primary preventions, such as self-management, home safety resources, and more intensive clinical care. Exercise programs have also been shown to strengthen the muscles of the lower limb and improve balance, and thus reduce the risk of falls and the fear of falling in people with OA, and could be considered for people with knee and hip OA. However, OA patients are different from the general population in many aspects, such as joint stability, balance, muscle strength, and bone quality; therefore, more research is needed to evaluate whether OA-specific screening tools could provide a more precise estimation for falls and fractures.

There were no statistically significant associations between symptomatic knee or hip OA and the risk of any fractures, including vertebral fractures. However, a recent study found that the associations of bilateral knee symptoms with the risk of fractures were attenuated and no longer statistically significant after further adjusting for falls. This finding is consistent with the study’s sensitivity analysis showing that symptomatic knee OA was associated with an increased risk of fractures. Thus, the potential role of knee OA in fractures cannot be ruled out.

While symptomatic hip OA was associated with an increased risk of recurrent falls, radiographic hip OA was associated with a decreased risk. It remains unclear whether sex has a modification effect on the association between OA and fracture risk. In a post-hoc study of a randomized controlled trial, women with knee pain or clinician-diagnosed knee OA were found to have a higher risk of fractures, but it is unknown whether the association between knee OA and fracture risk was stronger in women. In a recent study by the authors using data from the Osteoarthritis Initiative, however, they found that men with unilateral knee symptoms had a higher risk of fractures than women. Therefore, the role of sex in the association between OA and fracture risk needs further study.

A recent meta-analysis evaluated the association of knee and hip OA with the risk of falls and found that knee but not hip OA was positively associated with the risk of falls (RR: 1.46; P < 0.01), and that radiographic OA (knee and hip OA combined) was not significantly associated with fall risk (P > 0.05). This pooling of OA sites and of both symptomatic and radiological OA may be problematic given there are significant differences between knee and hip OA. Indeed, when the study authors updated the literature search and separated symptomatic and radiographic OA for both the knee and the hip, they found that while symptomatic knee and hip OA were both associated with an increased risk of recurrent falls (OR = 1.28, P < 0.05), radiographic knee OA was associated with an increased and radiographic hip OA with a decreased risk of falls (OR = 0.70, P < 0.05). More studies are needed in the future to examine these findings.

Conclusion

Symptomatic knee and hip OA were both associated with an increased risk of recurrent falls, and radiographic knee OA was associated with an increased risk of falls. No statistically significant associations of radiographic and symptomatic knee or hip OA with fractures were found. Symptomatic knee and hip should be considered as potential risk factors for falls and falls risk assessment and preventive interventions in people with OA at these sites considered.

Youyou Zhang is with the Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, 230032, Anhui, China.

Xiaoxi Li is with the Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, 230032, Anhui, China.

Yining Wang is with the Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, 230032, Anhui, China.

Faming Pan is with the Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, 230032, Anhui, China, and the Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Hefei, 230032, Anhui, China.

Tania Winzenberg is with the School of Medicine, University of Tasmania, Hobart, TAS, Australia, and the Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia.

Guoqi Cai is with the Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, 230032, Anhui, China, and with the Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia.