Total Knee Arthroplasty (TKA) is a common surgical treatment for severe knee Osteoarthritis (OA); the most frequently performed joint arthroplasty, improving pain, physical function, disability and health related quality of life (HRQoL) [1-6]. Key indications for TKA are generally agreed to be end-stage knee OA and persistent severe pain [7-11] Although there is a rapid and substantial improvement in knee pain, function and HRQoL after TKA, little is known about the frequency and history of falls as well as the factors affecting falling status in patients following TKA a year after surgery in comparison to pre-operative status.

Furthermore, few studies have included pre-operative and postoperative assessments of falls, and even fewer studies have identified the type and circumstances of falls, location and related impairments and disabilities in this population and simultaneously show the possible improvement in falls frequency a year after TKA in individuals with severe knee OA, along with the estimation of self administered questionnaires and physical performance tests, examining HRQoL and other parameters of patients life.

Therefore, the purpose of this study was to investigate and determine: a) the history and frequency of falls, including mechanism or causes of falls, injuries sustained from falls reported, activity during falling and location of falls, b) the factors affecting falls, a year after TKA in elderly patients with severe knee OA.

The demographic and clinical characteristics of the participants at the baseline are described in Table 1.

According to the results, there was a significant improvement in falling status of patients a year after total knee arthroplasty. In total, a year after surgery, 15 patients reported 20 falls, which defines the percentage of patients who had a fall a year after surgery at 22.1% (p<0.001), (Table 2). On the contrary, in the pre-operative measurement the proportion was 63.2% [13].

In general, there was 54.5% improvement of patients' falling status. According to the results, 23.5% of patients who were 1-time fallers preoperatively became non-fallers postoperatively, 20.6% were frequent fallers preoperatively became non-fallers postoperatively and 10.3% who were frequent fallers preoperatively became 1-time fallers postoperatively (Table 2).

The frequency of 1-time fallers postoperatively was 14.7% compared to 29.4% preoperatively. The majority of 1-time fallers became non-fallers postoperatively. Specifically from 29.4% of 1-time fallers preoperatively, only 2.9% remained 1-time fallers postoperatively, 2.9% became frequent fallers and 23.5% became non-fallers. Those who became 1-time fallers postoperatively were 10.3% of frequent fallers preoperatively and 1.5% of non-fallers preoperatively. The frequency of frequent fallers was 7.4% postoperatively compared to 33.8% post-operatively. The majority of frequent fallers became non-fallers postoperatively. Specifically from 33.8% of frequent fallers preoperatively, only 2.9% remained frequent fallers postoperatively, 20.6% became non-fallers postoperatively and 10.3% became 1-time fallers postoperatively. Those who became frequent fallers postoperatively were 1.5% of non fallers preoperatively and 2.9% of 1-time fallers preoperatively (Table 2).

According to the results of self administered questionnaires and physical performance tests, there was a significant improvement in the one-year postoperative measurement compared to preoperative (Table 3).

Concerning the characteristics of falls, an alteration was detected in all parameters, but statistically significant differences in the frequencies reported, referred to minor injury (p=0.002), frequency of stumbles (p=0.003), and the falls due to muscle weakness (p<0.001) (Table 4).

The history of falls and the presence of fear of falling statistically affected falling status (Table 5), whereas older age (Table 6), marginally affected falling status a year after TKA.

According to the multiple logistic regression, the history of falls increased 7.2 times the likelihood of falls, the presence of FOF increased 11.9 times the likelihood of falls and the annual increase of age over 65 years increased 1.13 times the likelihood of falls (Table 7).

A limited number of studies exists in the literature, describing the improvement in fall history and frequency a year after TKA, especially when comparing with the preoperative status in individuals with knee OA. A year after TKA the frequency of falls was 22%, significantly reduced compared to the frequency of 63.2% preoperatively. Pain relief, active movement and improved physical activity, which starts 3 months after the procedure and reaches its optimum level a year later, minimized that risk and reduced the post operative falls rate to 22.1% as recorded in our study, a figure that was lower to the one reported even for healthy community living older adult population [23-25]. The findings of this study do not permit us to determine the parameter, whose positive change precedes that of the others assessed in this study and succeeds in reversing the negative chain of pain, muscle weakness, instability, stiffness, disability and poor quality of life. It was though clear, that this chain was reversed a year after TKA, possibly finding the relief of pain on the top of the scale.

Apart from a significant reduction in the frequency of falls, an improvement of 54% in the falling status of patients was observed. The greater improvement was observed on the behavior of frequent fallers, since they improved their falling status from 33.8% to 7.4%. This group was more vulnerable since they fell more often and with the background of weakness and instability that characterizes them, they were in greater risk of injury. That change supported the belief, that the patients in our study regained their normal physical activity and balance and stopped being so unstable, like they were before due to severe knee OA. Nevertheless, there was a proportion of patients (19%), who maintained their falling status and remained fallers in both measurements, but that rate was considered to be within the normal limits of 30% of fallers among the elderly population.

Previous studies conducted with TKA patients have presented similar findings although not so positive, starting from Swinkels et al., (2009) [26], reporting a postoperative fall rate of 24.2%, Matsumoto et al., (2012) [27], reported fall rate of 32.9% and Levinger et al., (2012) [28], reported a fall rate at 40%. When comparing postoperative results to preoperative status, a significant difference was reported in fall rate, although Swinkels et al., (2009) [26], found almost the same results preoperatively and postoperatively and no significant difference. Additionally, Matsumoto et al., (2012) [27], didn’t have a preoperative measurement to compare and Levinger et al., (2012) [28], reported a reduction in fall rate from 48.5% to 40%, but that difference was not significant.

According to the literature the intrinsic risk factors that are responsible for 39% -53% of falls in the community older adult population are history of falls [23, 29, 30], advanced age [25, 31], gender [25, 31], muscle weakness, reduced physical activity [32], mobility disorders and abnormal gait [33-35], sedentary life [36], fear of falling [23, 37-39] chronic diseases [40, 41] and solitary life [42]. In the present study, the factors that affected falling status were the history of falls, fear of falls and advanced age. In addition the history of falls increased 7.2 times the likelihood of falls, whereas the presence of FOF increased 11.9 times the likelihood of falls. In contrast to other studies [26, 31, 39-41], a year after TKA, factors like chronic diseases, solitary life, reduced physical activity and gender didn’t affect falling status. Those factors seemed more likely to influence fear of falls rather than history of falls [43].

A year after TKA, the main cause of falls was tripping and stumbling and the majority of falls took place during walking. In most cases, the main cause of stumbling is minor. But the adjustment, reaction speed and muscle strength required to overcome the obstacle is beyond the ability of the elderly person to overcome [44]. Furthermore there was a notable minimization of the presence of muscle weakness as a cause of falls, indicating that most patients gradually regain satisfactory levels of muscle strength even though that was not measured directly.

The risk of fracture after TKA was also a matter of investigation. A year after TKA, when pain and stiffness was decreased and function was improved, we would expect that the risk of fracture would diminish as well. Nevertheless the reduction was not significant compared to the pre-operative evaluation. However, the result would be considered satisfactory, considering that studies with community older adult population report that approximately 1 in 10 falls result in a serious injury, of which 5% are fractures [14, 23, 29]. In our study that rate was 1 in 20 falls. On the other hand, there was a significant improvement in the frequency of minor injuries, which leads to the conclusion that the risk of serious injury decreased significantly after surgery compared to the preoperative evaluation.

The difference between indoor and outdoor falls was also a matter of interest. Although most elderly people spent their time primarily in their home [45] the studies indicate that at least 50% of falls take place outdoors [46-49]. Similarly in our study the frequency of outdoor falls was 65%.

Acknowledging the limitations of the study, we would identify the small number of patients because the research included only patients with severe knee OA a year after TKA. Nevertheless, there are numerous studies examining falls for community living elderly population but there are only few examining patients a year after TKA.

Based on the results of falls frequencies, falls characteristics and differentiation of falling status, we can conclude and support the belief that a year after TKA, patients with severe knee OA significantly reduced the frequency of falls and the consequent risk they provoke.

TKA generally improved a lot of aspects in patients’ life. One of these was the reduction of fall risk, which always co-exists in this population, causing devastating problems threatening the benefits of the procedure.