Prehabilitation, particularly in the form of exercise, has the potential to significantly improve preoperative and postoperative outcomes in patients with knee osteoarthritis who are undergoing total knee arthroplasty. Both physiological and psychological outcomes can be positively impacted.
By Carly McKay, PhD, and Harry Prapavessis, PhD
Osteoarthritis (OA) is a common condition, and its chronic symptoms of pain and joint stiffness are a leading cause of disability in those aged 65 years and older.1 The prevalence of knee OA, coupled with upward-shifting population demographics, means that the number of total knee arthroplasties (TKA) performed each year is on the rise.
Upwards of three million TKAs are projected to occur annually in the US by 2030.2 Clinicians report satisfactory outcomes in up to 95% of arthroplasty patients,3 but, while the operation is effective in terms of pain reduction, improving range of motion, and correcting joint alignment, a number of factors may affect a patient’s ability to achieve full function afterward. Regaining strength and mobility is key to attaining maximal benefit from the procedure,4 and it has been reported that those who have surgery earlier in the progression of OA generally have a better prognosis for achieving these gains than those with more severe symptoms.5 Additionally, the faster patients are able to become independently mobile and perform daily living activities after surgery, the better their functional outcomes.6
Given that presurgical function is the greatest predictor of postsurgical function,5 researchers have begun to examine the potential role of prehabilitation in patients undergoing TKA.7
What is prehabilitation?
The waiting period for elective procedures can be weeks or months. During this period, many conditions, including OA, continue to progress and the patient’s health and function deteriorate.8 Patients therefore undergo surgery in worse condition than when they were originally diagnosed, consequently requiring greater amounts of postoperative treatment to return to a healthy state.8 Furthermore, as patients awaiting surgery experience the progressive worsening of their condition, the time they spend engaging in daily living activities will likely decrease due to fatigue, pain, or a loss of motivation. To prevent declines in functional capacity associated with an increasingly sedentary lifestyle, some experts have advocated the implementation of presurgical exercise programs.4,7
The concept of presurgical intervention, or prehabilitation, has emerged in the literature as a potential means of ameliorating the effects of a prolonged waiting period on postoperative outcomes in a number of surgical populations, including those scheduled for colorectal and spinal surgery.
In general, the basic premise of prehabilitation is to increase the body’s functional capacity in preparation for surgery.4 It has been speculated that, by improving function, the patient will better withstand the physical and mental stressors of the procedure and will therefore require less intervention in the postoperative rehabilitation phase.7 Patients undergoing successful prehabilitation are thought to experience shorter recovery times, less dependence on caregivers after surgery, and a more rapid return to presurgical function than their counterparts receiving standard care.4,7,9
As an illustration, consider two hypothetical TKA patients. Both individuals begin at the same level of function in the preoperative phase, but the prehabilitation patient is able to increase his or her functional capacity before the surgery. Although both patients experience similar magnitudes of functional decline immediately following surgery, the prehabilitation patient retains a higher level of overall function, and is therefore able to recover to a minimal level of independence much faster. The degree of difference between the prehabilitation patient and the standard care patient is likely a function of the intensity, frequency, and duration of the prehabilitation intervention.4
One common concern is that exercise may exacerbate OA symptoms (primarily pain), and this concern can be enough to discourage patients from even considering exercise-based prehabilitation. There is, however, a large body of research suggesting that exercise is an effective nonpharmacological option for those with OA.
Evidence supporting the benefits of aerobic exercise has been reasonably persuasive. A meta-analysis conducted in 2004 identified 12 randomized controlled trials (11 targeting knee OA) investigating the effects of aerobic-based exercise interventions on OA symptoms.10 The results indicate that walking programs,11-14 jogging in water,14 and Tai Chi15,16 can have significant impact on pain, joint tenderness, and functional status for OA patients.10 Walking programs demonstrated particular efficacy for reducing pain and disability, with reductions in self-reported pain ranging from 29% to 47% and self-reported disability during daily living activities (such as bathing, dressing, and transferring from bed to a chair) decreasing approximately 15% to 20%.10
Strength training has also been consistently supported in the literature, with a recent systematic review identifying 18 studies that investigated the effects of lower limb strengthening on knee OA symptoms.17 Of these studies, 56% showed significant improvements in pain for resistance training groups versus controls.17 Strength training was also associated with significant improvements in physical disability in 79% of the studies in which it was measured.17 The effects of high-resistance (60% to 80% of one repetition maximum [RM]) training appear to be larger than the effects of low-resistance (10% to 50% of one RM) training,18 and isokinetic or isotonic exercises seem to be of greater benefit than simple range-of-motion or isometric exercises, as they develop functional strength in muscles used to perform daily living activities.19
Because many knee OA patients elect to have TKA after they have exhausted all pharmacological treatments, exercise may be the only management option remaining during the presurgical period. Considering its efficacy in OA populations and its potential to improve surgical outcomes, exercise is therefore the primary component of many prehabilitation interventions.
Education, physical therapy, and exercise have all been examined as prehabilitation modalities for TKA. A recent review of 11 studies (n = 1044), five of which included TKA patients, found that preoperative education reduced patient anxiety in three studies but had no significant effect in two others.20 Similar discrepancies were reported for pain and length of hospital stay.20 In a review of five studies investigating preoperative physiotherapy, three of which focused on TKA (n = 89), Ackerman and Bennell reported no significant effect on functional outcomes or length of hospital stay for TKA patients.21
Although a number of prehabilitation modalities have been investigated, exercise interventions are particularly attractive due to the physiological plausibility of their effect. Loss of lower extremity muscle strength is a strong predictor of reduced functional performance and stability during daily living activities,22,23 and it has been reported that muscle weakness is a better predictor of pain and disability than radiographic OA.24-26 Because quadriceps strength is one of the largest contributing factors to function for those with knee OA, increasing strength before surgery may allow patients to more quickly regain full function post-TKA and engage in a greater number of daily living activities in the long term. Cardiovascular fitness, healthy body weight, and optimal immune function are also crucial to recovery, as they allow patients to safely undergo anesthesia and fight off infection. Exercise can help patients to achieve these health prerequisites as well, further supporting its role in presurgical treatment.
Not surprisingly, the evidence supporting exercise as a prehabilitation intervention has been somewhat more positive than the evidence for other modalities. For TKA patients, it has been reported that exercise-based interventions produce improvements in preoperative and postoperative sit-to-stand tests,27,28 as well as postoperative stair ascent and descent tests27,29 relative to those receiving standard care. Although there is some support for using exercise prehabilitation to improve six-minute walk distance,28 researchers have also found contradictory evidence related to that outcome measure.29 Additionally, patients have self-reported positive effects of exercise on preoperative function.28,30 Some evidence suggests exercise improves postoperative self-reported function,28 but other studies have shown no effect30 or have suggested that exercise causes steeper immediate declines postoperatively compared to a control condition.31 It has also been shown that exercise interventions may allow patients to walk further at discharge than those receiving standard care. 30
Furthermore, TKA patients participating in exercise prehabilitation have shown greater improvements in preoperative lower limb strength than controls.29,30 Estimates suggest that prehabilitation patients may demonstrate as much as a 54% increase in quadriceps strength following a four- to six-week intervention.29 Postoperatively, exercise prehabilitation has resulted in significantly greater extension strength improvements based on within-group analyses (ie, prehabilitation patients improved significantly from pre- to postoperation),27 but there has been no significant strength difference when comparing control groups (ie, no significant difference between prehabilitation and standard care patients after surgery).30
Although the effect of exercise prehabilitation on function and strength is encouraging, its effect on pain is unclear. There is some evidence that exercise-based interventions in patients undergoing TKA result in significant pain reductions in the presurgical and postsurgical periods,28,29 although there may be a slight increase in preoperative pain for those engaging in aerobic-based exercise.31 Other studies have found no significant postoperative effect on pain.27,30,32
A pilot study we recently conducted examined the effect of a prehabilitation intervention based on lower limb strength training.32 Twenty-two TKA patients with similar baseline strength were randomized to either an intervention training group or a placebo training group (which performed upper body exercises only), and exercised three times per week for six weeks before surgery. We found that the intervention had a large effect on quadriceps strength before TKA [F(3,18) = 0.89, p = 0.47, effect size η2 = 0.13], although there was no significant difference between groups after surgery. There was also a large effect on preoperative walking speed [F(3,18) = 1.47, p = 0.26, η2 = 0.20], but no significant effect on postoperative walking speed, stair ascent and descent speed, pain, or self-reported function.32
Our results indicate that, although there may not be statistically significant improvements following strength-training prehabilitation, there may be clinically meaningful improvements in strength and mobility before surgery. This suggests that prehabilitation may be beneficial to patients during the preoperative period while they are awaiting TKA. Moreover, as this was a pilot study, it may have been underpowered to detect postoperative differences between prehabilitation patients and controls. We recommend conducting larger studies to examine the postoperative effects of this particular type of intervention.
Although researchers have looked at the role of psychological variables in arthroplasty outcomes, they have not generally included them in prehabilitation studies in this population. Considering that prehabilitation is predicated on the notion of preparation for both the physical and mental stressors of surgery,7 there is a paucity of information regarding the ability of such an intervention to successfully influence preoperative psychological variables.
Of all the psychological variables that could potentially influence TKA outcomes, arthritis self-efficacy is perhaps the one most deserving of research consideration. Arthritis self-efficacy characterizes the patient’s self-confidence in managing his or her symptoms while performing daily living tasks. It has been shown that preoperative self-efficacy and expectancies can explain, on average, 10% of the outcome variance in self-reported pain, function, and health-related quality of life for TKA patients.33 Similar findings have been reported for objective measures of function, with van den Akker-Scheek and colleagues reporting that preoperative self-efficacy significantly predicted walking speed six months after knee or hip arthroplasty (coefficient of determination, R2 = 0.47).34
Postoperative self-efficacy has been shown to influence surgical outcomes to an even greater extent than preoperative self-efficacy.34-37 Moon and Backer examined the effect of immediate postoperative self-efficacy on ambulation frequency and exercise performance the day following joint replacement, and found that it accounted for 8% to 33% of the variance.37 This is echoed in the findings of van den Akker-Scheek et al, who found that postoperative self-efficacy was a significant predictor of long-term physical and mental functioning (R2 = 0.30 and R2 = 0.53, respectively).34Self-efficacy may therefore help clarify some of the discrepancies in previous prehabilitation research, although to date it has not been well examined in this context. In our own work, after adjusting for baseline self-efficacy, participants exhibited a significant increase in arthritis self-efficacy from baseline to 12 weeks post-TKA, but the six-week strength-training prehabilitation intervention failed to elicit a significant treatment effect [F(3,18) = 0.51, p = 0.08, η2 = 0.08] (Figure 1).32 In this study, arthritis self-efficacy at all time points (baseline, preoperative, and six and 12 weeks post-TKA) was significantly correlated with preoperative quadriceps strength (correlation coefficient range: r = 0.43 to 0.49).38
Overall, the improvements in arthritis self-efficacy in this study were tied to symptom reductions over time, although the relationship between quadriceps strength and self-efficacy may point to an important role for prehabilitation. Future studies examining this relationship will be crucial for our understanding of how strength may impact self-efficacy, and vice-versa, and how to design prehabilitation interventions to enhance this positive interaction.
In summary, prehabilitation has the potential to improve both preoperative and postoperative function for TKA patients. Although research has not yet determined the intervention design and dosage that will impart the greatest benefit to patients, a growing body of evidence supports exercise-based interventions for positively impacting patient outcomes. Therefore, researchers and clinicians should continue to pursue the development of prehabilitation interventions as an arthroplasty adjunct.
Carly McKay, PhD, is a postdoctoral fellow in the Sport Injury Prevention Research Centre at the University of Calgary in Alberta, Canada. Harry Prapavessis, PhD, is a professor and faculty scholar in the Exercise & Health Psychology Laboratory, School of Kinesiology, at Western University in London, Ontario, Canada.
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