Patients performing G-EXE in addition to regular ambulation and activities-of-daily-living exercises demonstrated greater changes in knee ROM, quadriceps strength, and knee pain than those performing I-EXE in addition to regular ambulation and activities-of-daily-living exercises. The nonrandomized, asynchronous design decreases certainty of these findings.

Changes in ROM of knee flexion and extension ( P <.001) and quadriceps strength ( P <.001) were significantly better in the G-EXE group than those in the I-EXE group at discharge. The pain intensity improved more in the G-EXE group than in the I-EXE group at discharge ( P <.001). However, the changes in the timed up-and-go scores were not significantly different.

Two hundred thirty-one patients participated in G-EXE in addition to regular ambulation and activities-of-daily-living exercises twice daily during the hospital stay. Outcomes were compared to those of a retrospectively identified, historical control group (I-EXE group [n = 206]) that included patients who performed exercises identical to those performed by the G-EXE group. The outcomes included knee ROM, quadriceps strength, pain intensity, and timed up-and-go test score at 1 month before surgery and at discharge. Analyses were adjusted for age, body mass index, sex, length of hospital stay, and preoperative values.

To determine the effects of G-EXE during the acute recovery phase after TKA on knee ROM, quadriceps strength, functional ability, and knee pain.

The extent to which group-based exercise (G-EXE) improves knee range of motion (ROM), quadriceps strength, and gait ability is similar to that of individualized exercise (I-EXE) at 6 weeks and 8 months after total knee arthroplasty (TKA). However, the benefits of G-EXE for patients during the acute recovery phase after TKA remain unclear.

Total knee arthroplasty (TKA) is the most common surgical intervention for knee osteoarthritis (OA), offering patients pain relief, functional recovery, and improved quality of life.5,16 The early initiation of postoperative rehabilitation to increase range of motion (ROM) and quadriceps strength is a well-accepted concept and is considered important for obtaining the maximum benefit from knee arthroplasty.18–20 Additionally, in recent years, early hospital discharge has been increasingly supported worldwide because it leads to a significant decrease in the length of hospital stay.14,24 However, a shorter hospital stay may limit opportunities for postoperative rehabilitation, thus preventing patients from maximizing ROM, muscle strength, and function prior to discharge.

Group-based exercise (G-EXE) can provide therapy for several patients simultaneously and offers advantages, such as cost-effectiveness28 and positive impact on physical function, for community-dwelling elderly adults4,25 and individuals with severe OA.1,2,13 Previous studies investigated the effect of G-EXE at 6 weeks23 and 8 months8 after TKA and indicated that G-EXE improves knee ROM, quadriceps strength, and gait ability to an extent similar to that of individualized exercise (I-EXE). However, the benefits of G-EXE for patients during the acute recovery phase after TKA remain unclear. Timonen et al31 found that G-EXE is more effective than I-EXE at improving muscle strength during the acute recovery phase from illness when mobility is impaired; therefore, G-EXE is also expected to be more effective than I-EXE during the acute recovery phase after TKA. Physical therapists must help patients maximize their ROM, muscle strength, and functional ability during the short hospital stay; thus, investigations into the effects of G-EXE during the acute recovery phase after TKA are needed. The purpose of this study was to determine the effects of G-EXE as compared to I-EXE during the acute recovery phase after TKA on knee ROM, quadriceps strength, functional ability, and knee pain.

Methods This study was a prospective observational study in patients undergoing TKA and included a historical control group. The patients were examined 1 month before the surgery and at hospital discharge. We introduced G-EXE into postoperative inpatient rehabilitation after TKA at our institution on April 1, 2012. We consecutively recruited 245 patients who were scheduled for TKA from April 1 to August 31, 2012 and met the following inclusion criteria for the G-EXE group: (1) an age of between 50 and 80 years and (2) the completion of primary unilateral TKA for knee OA staged as grade 4, based on the Kellgren-Lawrence radiographic grading system.17 The exclusion criteria were (1) the presence of uncontrolled hypertension or diabetes, (2) neurologic impairments, (3) coexisting OA or other orthopaedic conditions in the contralateral hip or knee affecting mobility, and (4) a diagnosis of rheumatoid arthritis. Fourteen patients were excluded because of neurologic impairments (n = 2), coexisting OA affecting mobility (n = 8), and rheumatoid arthritis (n = 4). Ultimately, 231 patients were included in the G-EXE group after providing informed consent. The historical control group (I-EXE group) included 217 patients who underwent TKA before G-EXE introduction (from November 1, 2011 to February 29, 2012) and met the inclusion and exclusion criteria described above. Eleven patients were excluded because of neurologic impairments (n = 1), coexisting OA affecting mobility (n = 7), and rheumatoid arthritis (n = 3). We ultimately included 206 patients in the I-EXE group. This study did not use a randomized design. Although the historical control design could have introduced differences in group characteristics, the shorter recruitment and trial periods and the large sample size reduced the differences in group characteristics and strengthened the study. Therefore, we used a historical control design and included a large sample size in less than 1 year. The study was approved by the Ethics Committee of Anshin Hospital in Kobe, Japan. All patients in both groups underwent primary unilateral TKA, performed by 4 surgeons. Patients in both groups were subjected to identical surgical procedures and identical anesthetic procedures. In both groups, all surgical procedures used the medial parapatellar approach and posterior-stabilized knee replacement. A pneumatic tourniquet was used during all surgeries. At the end of surgery, all patients received the same drug cocktail to ensure effective pain control. Additionally, the postoperative pain control program was the same for both groups. The same postoperative ambulation and activities of daily living (ADL) exercise program was administered to all patients by 5 physical therapists with 3 to 6 years of experience. All patients performed ambulation and ADL exercises for 20 minutes each, twice daily, from the day after the surgery to the day before discharge. On the day after surgery, patients learned to transfer (eg, from a bed to a chair) and walked using a walker, bearing as much weight as tolerable. After independent ambulation was achieved using a walker, ambulation exercises using a cane were introduced. Patients then learned to ascend/descend stairs. The primary mobility-related goal at discharge in both groups was independent ambulation using a cane. In addition to performing ambulation and ADL exercises for 20 minutes each, all patients in the G-EXE group participated in a 30-minute G-EXE session supervised by a physical therapist (twice daily) from the day after the surgery to the day before discharge. One session of G-EXE included 6 patients and comprised 15 minutes of ice massage, 15 repetitions of ankle pumps, hip rotations without load, quadriceps setting without load in a neutral hip position, and active-assisted heel slides in the long-sitting position, intended to alleviate pain and improve knee ROM and muscle strength (TABLE 1, FIGURE 1). No changes were made in exercise intensity or procedures during hospitalization. TABLE 1 Exercise Protocol Description Pain and swelling control Ice massage for 15 min Strengthening Quadriceps setting without load with neutral hip position for 15 repetitions

Ankle pumps for 15 repetitions

Hip rotations without load for 15 repetitions Range of motion Active-assisted heel slides in long-sitting position for 15 repetitions Download Figure Download PowerPoint FIGURE 1. Photographs of the exercises performed. (A) Ice massage, (B) quadriceps setting, (C) ankle pumps, (D) hip rotations, and (E) active-assisted heel slides. From the day after surgery to the day before discharge, all patients in the I-EXE group individually performed the same exercises for 30 minutes twice daily, including 15 minutes of ice massage, under the supervision of a physical therapist. The I-EXE was performed in addition to the regular ambulation and basic ADL exercises. Patients in both groups performed 20 minutes of ambulation and ADL exercises, and 30 minutes of group-based or individualized exercise, in the morning and afternoon from the day after surgery to the day before discharge. The difference between the G-EXE and I-EXE groups was that individuals in the G-EXE group performed the exercises in a group setting and those in the I-EXE group performed the exercises individually. Data were collected 1 month before surgery and at discharge, and included the patients' age, sex, body mass index (BMI), knee ROM, quadriceps strength, functional ability, and knee pain. Knee ROM was measured using a standard long-arm goniometer. The axis of the goniometer was aligned with the center of the lateral epicondyle of the femur. The distal arm of the goniometer was aligned with the lateral malleolus, and the proximal arm was aligned with the greater trochanter of the femur. Passive knee flexion and extension ROM were performed in the supine position. Quadriceps strength of the involved limb was measured as the peak isometric knee extension torque (Newton meters per kilogram) using a handheld dynamometer (µTas F-1; ANIMA Corporation, Chofu, Japan). Participants were seated with the hip flexed to 90° and the knee flexed to 75°.26 The sensor of the handheld dynamometer was fastened to the shin with a Velcro strap, while a belt was used to restrain it and enhance the reliability of the isometric leg muscle strength measurements (FIGURE 2).15 The positioning of the dynamometer was recorded at the initial testing of each subject, and an identical setup was used for each subsequent strength assessment. Participants were instructed to extend their knee maximally for approximately 3 seconds. Verbal encouragement was provided to facilitate maximal volitional force production. The peak torque was estimated as the product of the force and distance between the attachment of the dynamometer and knee joint. Two attempts at maximal contraction were performed, and the trial with the highest volitional force production was normalized to body weight and used for analysis. Download Figure Download PowerPoint FIGURE 2. Photograph of the quadriceps strength measurement setup. Functional ability was assessed using the timed up-and-go (TUG) test.29 The TUG test measures the time it takes a participant to rise from an armless chair (seat height, 40 cm), walk 3 m, turn, and return to sitting in the same chair. Participants were instructed to walk as quickly as possible so long as they felt safe and comfortable. For the TUG score, the average of 2 subsequent trials was used for analysis. Assistive devices were allowed only if the participant felt unsafe or could not complete the test without the assistance of a cane. Pain score was collected after patients answered the question, “In the last 24 hours, how would you rate your overall pain at rest and then on movement, with 0 being no pain and 10 being the worst imaginable pain?” This measure gave an integer pain score ranging from 0 to 10, with 0 as no pain and 10 as maximal pain.22 The normality of the parameter distribution was verified by the Shapiro-Wilk test. First, patients who dropped out from the standard postoperative rehabilitation program or could not complete the test at discharge in both groups were compared with patients with complete preoperative and postoperative data using assessments of age, BMI, preoperative knee ROM, quadriceps strength, TUG scores, and pain scores using Student's t test. Additionally, differences in sex between patients who dropped out of the standard postoperative rehabilitation program or could not complete the test at discharge and patients with complete preoperative and postoperative data were evaluated using the chi-square test. Second, Student's t test was used to compare age, BMI, preoperative knee ROM, quadriceps strength, TUG scores, pain scores, and length of hospital stay between the 2 groups. The chi-square test was also used to investigate differences in sex between the 2 groups. Third, a multiple regression analysis using forced entry was used to determine the effects of G-EXE on knee ROM, quadriceps strength, functional ability, and knee pain, but included only patients with complete preoperative and postoperative data. The dependent variables included outcomes (knee ROM, quadriceps strength, TUG scores, and pain scores) at discharge and the independent variables included groups (G-EXE versus I-EXE). The independent variables also included age, sex, BMI, length of hospital stay, and preoperative score as the covariates (eg, when the group difference in quadriceps strength was tested, quadriceps strength at baseline was used), because the preoperative values for knee ROM, quadriceps strength, functional ability, and knee pain reportedly affect postoperative values.3,27,33 All statistical testing was performed at a level of significance of .05. Analyses were conducted using SPSS Version 22.0 (IBM Corporation, Armonk, NY).

Results This study included 437 patients who underwent primary TKA. Of the 437 patients initially enrolled in this study, 4 patients in the G-EXE group (1.7%) dropped out because of a requirement for secondary suturing due to failure of healing (n = 1, 0.4%) and health conditions unrelated to the study (n = 3, 1.3%). In the I-EXE group, 3 patients dropped out because of a requirement for secondary suturing due to failure of healing (n = 1, 0.5%) and health conditions unrelated to the study (n = 2, 1.0%) (FIGURE 3). We found no significant differences in age, BMI, sex, preoperative knee ROM, quadriceps strength, TUG scores, or pain scores between the 7 patients who dropped out and the 430 patients with complete preoperative and postoperative data (all, P>.05). Download Figure Download PowerPoint FIGURE 3. Flow of the study. Abbreviations: G-EXE, group-based exercise; I-EXE, individualized exercise. The final analyses included 227 patients in the G-EXE group and 203 patients in the I-EXE group (TABLE 2, FIGURE 3). There were no significant differences in baseline age, BMI, sex, preoperative knee ROM, quadriceps strength, TUG scores, or pain scores between the 2 groups. The mean length of hospital stay of the G-EXE group (6.2 ± 0.4 days) was significantly shorter than that of the I-EXE group (7.9 ± 0.8 days) (P<.001) (TABLE 2). All patients in both groups participated in G-EXE or I-EXE, in addition to the regular ambulation and ADL exercises, daily from the day after surgery to the day before discharge. TABLE 2 Characteristics of the Participants at Baseline and at Discharge* Characteristic I-EXE Group (n = 203) G-EXE Group (n = 227) Baseline Age, y 71.1 ± 6.8 (51–79) 70.6 ± 7.2 (51–79) Sex (female), n (%) 181 (89.2) 205 (90.3) Body mass index, kg/m2 26.9 ± 4.0 (19.2–34.3) 27.1 ± 4.6 (20.0–33.4) Discharge Length of hospital stay, d 7.9±0.8 (6–9)† 6.2±0.4 (6–8)† Exercise and treatment sessions, n 11.5±0.8 (8–14)† 8.3 ± 0.8 (8–12)† Patients in the G-EXE group displayed significantly greater knee flexion ROM at discharge than those in the I-EXE group (P<.001; adjusted mean difference between groups, 6.0°; 95% confidence interval [CI]: 4.2°, 7.9°) (TABLE 3). At discharge, patients in the G-EXE group exhibited significantly better knee extension ROM than those in the I-EXE group (P<.001; adjusted mean difference between groups, 5.0°; 95% CI: 4.1°, 6.0°) (TABLE 3). Patients in the G-EXE group exhibited significantly better quadriceps strength at discharge than those in the I-EXE group (P<.001; adjusted mean difference between groups, 0.21 Nm/kg; 95% CI: 0.17, 0.25 Nm/kg) (TABLE 3). However, there were no significant differences in TUG scores (P = .52) (TABLE 3). Mean pain score at discharge in the G-EXE group was significantly lower than that of the I-EXE group (P<.001; adjusted mean difference between groups, 2.0; 95% CI: 1.5, 2.4) (TABLE 3). TABLE 3 Measurements of the Participants at Baseline and on the Day of Discharge* I-EXE Group (n = 203) G-EXE Group (n = 227) Outcome Preoperative Postoperative Preoperative Postoperative Adjusted Mean Group Difference at Discharge† P Value‡ Knee flexion ROM, deg 121.6 ± 19.9 86.2 ± 9.9 124.2 ± 17.8 94.0 ± 6.5 6.0 (4.2, 7.9) <.001 Knee extension ROM, deg −8.8 ± 6.4 −6.0 ± 5.3 −7.9 ± 5.5 −0.8 ± 2.2 5.0 (4.1, 6.0) <.001 Quadriceps strength, Nm/kg 0.81 ± 0.30 0.30 ± 0.17 0.83 ± 0.3 30.50 ± 0.13 0.21 (0.17, 0.25) <.001 TUG test score, s 11.4 ± 3.8 16.2 ± 5.8 11.8 ± 4.9 15.8 ± 4.7 0.3 (−0.7, 1.3) .52 Pain score 4.0 ± 2.1 3.7 ± 1.7 4.1 ± 2.3 2.1 ± 1.4 2.0 (1.5, 2.4) <.001

Discussion According to the results of this study, knee ROM scores were significantly higher, quadriceps strength was significantly greater, and knee pain score was significantly lower at discharge in the G-EXE group than in the I-EXE group. Moreover, the TUG scores were similar between the 2 groups. These results indicate that G-EXE during the acute recovery phase after TKA was highly effective for the improvement of knee ROM and quadriceps strength and alleviation of knee pain. Previous studies regarding G-EXE after TKA showed that the effects of G-EXE were similar to the effects of I-EXE on physical function.8,23 One reason for the difference in the results between our study and a previous study23 is the participation ratio in G-EXE. Madsen et al23 found no difference in knee ROM and quadriceps strength between G-EXE and I-EXE groups; however, only 31% of patients completed all G-EXE sessions in their study. In our study, all patients in the G-EXE group completed all G-EXE sessions; therefore, increasing attendance at G-EXE sessions may be necessary to enhance the effects of G-EXE. Another possible reason for the effectiveness of G-EXE in our study is that we conducted early-onset G-EXE in inpatients during the acute recovery phase after TKA, whereas 2 previous studies conducted late-onset G-EXE in patients 6 weeks23 and 8 months8 after TKA. Timonen et al31 found that 10-week G-EXE during the acute recovery phase from illness, when mobility is impaired, was more effective than I-EXE in improving lower-limb muscle strength. In the present study, we also conducted G-EXE during the acute recovery phase, and this early introduction of G-EXE may account for the differences from previous studies.8,23 However, the length of our intervention was shorter than that of a previous study,31 and some short-term follow-up would have added insight with respect to the efficacy of the intervention. Therefore, further study should assess the effects of the length of the intervention on achieving maximum benefit. In elderly adults, exercise motivation has an impact on the effort expended during exercise32 and the results of exercise.7 The G-EXE group had more opportunities for social interaction with other patients than the I-EXE group did, and social interaction is a primary motivator for elderly people to exercise.30 Exercise motivation can also be increased by class instruction and peer support,10 and G-EXE can increase exercise motivation among participants.11,21 Therefore, increasing exercise motivation by implementing G-EXE may provide an advantage over I-EXE. Additionally, it is reported that exercise motivation is related to pain.7 In the current study, reduced pain in the G-EXE group may also be related to exercise motivation. At discharge, patients in the G-EXE group demonstrated better flexion (6°) and extension (5°) ROM than those in the I-EXE group. Additionally, patients in the G-EXE group had a mean pain score that was 2 points lower than that in the I-EXE group at discharge. Five degrees of knee ROM6,20 and 2 points on a pain score12 are considered minimal clinically important differences. We found positive effects of G-EXE as compared to I-EXE on knee ROM and pain scores during the acute recovery phase after TKA; however, the group differences at discharge were similar to the minimal clinically important differences. Therefore, greater effort is needed to increase G-EXE effectiveness during the acute recovery phase after TKA. Six patients simultaneously performed exercises in the G-EXE group. We found that the mean length of hospital stay in the G-EXE group was significantly shorter than that in the I-EXE group. Therefore, we believe that G-EXE more effectively improves knee ROM, quadriceps strength, and knee pain and reduces costs. However, a further study should assess the cost-effectiveness of G-EXE during the acute recovery phase after TKA. There are limitations that should be considered when interpreting these results. First, we used a historical control study design rather than a randomized controlled trial design, which might have introduced systematic differences, including population differences. Preoperative factors including age, BMI, sex, knee ROM, quadriceps strength, functional ability, and knee pain were similar between the 2 groups; however, there may also be differences in unobserved factors. Additionally, the historical control may include potential differences in actions or judgments of the patients, surgeons, or physical therapists at different time points. This design introduces a risk of selection bias or information bias, such as observer expectation bias, participant expectation bias, or Hawthorne bias. Second, we did not evaluate the psychosocial benefits of G-EXE. One study reported that G-EXE provided a psychosocial benefit to elderly adults,9 which suggests that it may provide the same psychosocial benefit to patients in the G-EXE group in this study. However, further studies are needed to investigate the psychosocial effect of G-EXE in patients during the acute recovery phase after TKA.

Conclusion In conclusion, patients performing G-EXE in addition to regular ambulation and ADL exercises demonstrated better knee ROM, quadriceps strength, and knee pain at discharge than those performing I-EXE in addition to regular ambulation and ADL exercises. Patients benefit from G-EXE during hospitalization in the acute recovery phase after TKA.