Abstract
After total knee arthroplasty (TKA), persistent quadriceps muscle atrophy and weakness impairs physical function. Blood flow restriction (BFR) exercise is emerging as a potential method to improve muscle size and strength in clinical populations with orthopedic limitations. There are no randomized controlled studies documenting BFR exercise after TKA. This case report describes the use of home-based BFR exercise to increase quadriceps size, strength, and physical function after TKA.
A 59-year-old man (6 months post-TKA) performed body weight and walking exercises with BFR 5×/wk for 8 weeks. Blood flow in the TKA leg was restricted using a thigh cuff inflated to 50% of limb occlusion pressure. Lean leg mass, vastus lateralis thickness, knee extensor strength, and physical function were measured at baseline (6 months post-TKA), posttraining (8 months post-TKA), and long-term follow-up (14 months post-TKA).
After training, lean leg mass, vastus lateralis thickness, and knee extensor strength in the TKA leg increased by 4%, 14%, and 55%, respectively. Compared with baseline, posttraining knee extensor strength symmetry (TKA/uninvolved leg) increased from 64% to 98%. The patient’s performance improved for the 30-second chair stand, 40-m fast walk, and 6-minute walk tests. Increased quadriceps and physical function were maintained at the long-term follow-up.
With enhanced quadriceps and physical function, the patient resumed independent physical activity. Muscle and strength gains surpassed those typically reported after TKA. Outcomes suggest that home-based BFR exercise was feasible, safe, and effective. BFR exercise after TKA is promising and warrants further research.
Each year, more than 650,000 total knee arthroplasty (TKA) surgeries are performed to treat end-stage knee osteoarthritis.1 Annual costs associated with TKA are $11 billion2 and will increase dramatically as the number of surgeries reaches 3.5 million by 2030.1 After a TKA surgery, knee joint pain is reduced in most individuals.3 However, surgery also has a profound impact on quadriceps muscle size and strength. For example, quadriceps strength is substantially reduced after surgery, improves between 3 and 6 months, and reaches a level that is ~80% of the uninvolved leg (for a review, see reference4). Persistent quadriceps weakness after TKA is associated with altered gait mechanics5 and reduced physical function.6 Moreover, muscle weakness in older adults is a risk factor for falls.7 Accordingly, developing effective rehabilitation strategies to restore quadriceps muscle size and strength is imperative so that individuals with TKA can maintain adequate functional mobility and avoid further long-term disability.8–12
Several barriers make it difficult to regain quadriceps size and strength after TKA. First, typical exercise loads (60–80% of 1-repetition maximum) required to trigger muscle and strength adaptations are not always feasible because they may increase pain and/or joint irritation. Second, time requirements for complete restoration of quadriceps size and strength can be excessive for some patients. Third, access to specialized equipment for enhancing quadriceps muscle strengthening after hospital or outpatient discharge may be limited. Implementation of blood flow restriction (BFR) exercise is emerging as a safe and useful method to increase muscle size and strength in clinical populations with orthopedic limitations.13 This exercise mode involves lifting low loads (20–30% of 1-repetition maximum) while a pressurized cuff reduces blood flow.14 Specifically, cuff pressure is set low enough to partially maintain arterial blood flow to working muscles but high enough to prevent most venous blood flow from returning to the heart. Exercise with BFR is advantageous13,14 because increases in muscle size and strength are elicited using low loads, and strength gains can be achieved faster than traditional exercise. This modality can also be used with both resistance and aerobic exercise. The possibility of using BFR after TKA is intriguing,15 but there are no randomized controlled studies documenting BFR exercise after TKA. Our purpose was to describe the use of an 8-week home-based BFR exercise program with a patient who had leveled off in their recovery at 6 months post-TKA. We envisioned that BFR exercise would be safely tolerated, increase quadriceps size and strength, and enhance physical function.
Case Description
Patient
A 59-year-old male (body mass: 85 kg, height: 1.81 m, body mass index: 22; body fat: 31%) with a history of knee osteoarthritis presented pain and edema in his left knee. The patient developed an antalgic gait, experienced difficulty with reciprocal stair climbing/descending, and was unable to participate in his regular physical activity program of 5–6×/week of walking/cycling in the summer months and ice hockey/Nordic track during the winter months. A unilateral TKA procedure was performed to alleviate the osteoarthritic pain. The patient completed 11 weeks of outpatient physical therapy focusing on knee range of motion, lower extremity strengthening, balance, gait, and functional activities training. According to the medical record at discharge from physical therapy, the patient had an active knee range of motion of 6 to 131°, 4/5 quadriceps strength, and was ambulating independently without an assistive device. At the time of our initial interview, the patient reported he was 6 months postsurgery with full functional knee range of motion and adequate strength for independent ambulation. He had mild knee joint pain (1.8 cm using a 0- to 10-cm visual analog scale), slight edema, and self-reported weakness in the left quadriceps. The patient exhibited an intermittent antalgic gait and difficulty with reciprocal stair climbing/descending. With the long-term goal of returning to his walking, cycling, and ice hockey activities, the patient needed to achieve increased strength to resume such activity. The patient described a “plateau” in his recovery, as increased exercise intensity through strength training was not tolerable secondary to knee discomfort.
Examination: Baseline, Posttraining, and Long-Term Follow-up
The experimental procedures described here were approved by our university institutional review board and the patient gave informed written consent. Muscle size, strength, and physical function were evaluated at baseline (6 months post-TKA), posttraining (8 months post-TKA), and long-term follow-up (14 months post-TKA). Lean leg mass was assessed using dual energy x-ray absorptiometry (Discovery Wi, Hologic Inc, Marlborough, MA, USA). According to the manufacturer, the coefficient of variation (COV) of this system for the measurement of lean and fat mass has been reported to be 0.6 to 1.4%, and 1.8 to 2.1%, respectively.16,17
Thickness of the vastus lateralis was measured separately in the TKA and uninvolved legs using B-mode ultrasound (Logiq e BT12, GE Healthcare, Chicago, IL, USA). The patient was positioned supine with knees resting comfortably at an angle of 10° with a rolled towel placed under the knee for support. The scanning probe was used to image the muscle. Images of the vastus lateralis were taken at 66% of the distance from the anterior superior iliac spine to the proximal patella, and thickness was measured as the widest distance between the superficial and deep aponeurosis.18 Measurements were assessed 5×/d on 2 separate days (COV = 1.7%) and averaged over the 2 days. The same investigator performed all of the muscle thickness measurements and analyzed those using saved images.
Knee extensor strength was measured during a break test19 using a hand-held dynamometer (Microfet, Hoggan Health Industries, Inc., Murray, UT, USA). The patient performed 4 brief maximal contractions (~5 seconds) on 3 separate days. A 1-minute rest was provided between contractions. The average of the 3 closest contractions within each day was used for analysis (COV = 4.7%), and knee extensor strength symmetry was calculated as: [(TKA leg – uninvolved leg)/(uninvolved leg)]. Physical function20 was assessed using the 30-second chair stand, stair climb (9 stairs, stair height 18.8 cm), 40-m fast walk, and 6-minute walk tests. Functional tests were performed 1×/d on 2 separate days and the average values were used for analysis. These physical function tests are reported to have good reliability.21
Overview of the home-based blood flow restriction (BFR) program consisting of body weight and walking exercises. The patient performed this ~25-min exercise routine 5×/wk for 8 weeks. LOP = limb occlusion pressure; TKA = total knee arthroplasty.
Intervention
An overview of the home-based BFR exercise program is illustrated in Figure 1. The patient performed BFR exercise 5×/wk for 8 weeks. Each session consisted of 3 exercises (single-leg knee extension, body weight half-squats, walking) and took ~ 25 minutes to complete. First, the patient performed 3 sets of 30 seated single-leg knee extensions using his TKA leg with a 12-inch Thera-Band (90–0°). During the program, Thera-Band resistance increased from yellow (first 20 sessions) to red (next 7 sessions) to green (final 13 sessions). Next, the patient performed 3 sets of 30 double-leg bodyweight half-squats. Specifically, the patient was instructed to start from a standing position, lower his body until his knee angle reached ~45°, and then slowly rise back up. Finally, the patient performed 3 sets of 2-minute walking intervals at a self-selected speed. Throughout the session a 1-minute rest period was provided between sets and 2 minutes of rest was given between exercises. During each exercise, TKA leg blood flow was restricted using an 18-cm-wide aneroid sphygmomanometer (Briggs, Healthcare, Waukegan, IL, USA). The cuff was wrapped around the proximal part of the thigh and inflated to 108 mm Hg, which represented 50% of the pressure required to completely occlude blood flow in the femoral artery as assessed in the seated position (216 mm Hg). Moderate cuff pressures between 50% and 80% of limb occlusion pressure are appropriate for use with low-load resistance exercise.14 The cuff remained inflated during the 1-minute rest between sets but was deflated during the 2 minutes of recovery between exercises. Accordingly, blood flow was partially occluded for a total of ~18 minutes. It is important to note that limb occlusion pressure was determined only at the beginning of the program. During the exercise training sessions, cuff pressure was frequently checked by having the patient return to a seated position during the rest periods. If the pressure had dropped slightly, the patient would then inflate the cuff back to the prescribed pressure. Each week the patient visited the laboratory to perform 1 supervised session to verify proper movement form and cuff pressure. Before and after each session, the patient recorded any level of quadriceps muscle soreness and knee joint pain (0–10 visual analog scale).
Alterations in Physical Functiona
| Functional Test | Baseline 6 mo Post-TKA | Posttraining 8 mo Post-TKA | Follow-Up 14 mo Post-TKA | Change b | MCII |
|---|---|---|---|---|---|
| 30-s chair stand (reps) | 15 | 27 | 31 | 12c | 2–3 |
| Stair climb test (s) | 7.2 | 5.9 | 5.2 | −1.3 | −5.5 |
| 40-m fast walk (m/s) | 2.1 | 3.0 | 3.0 | 0.9c | 0.2–0.3 |
| 6-min walk (m) | 696 | 774 | 800 | 78c | 60 |
| Functional Test | Baseline 6 mo Post-TKA | Posttraining 8 mo Post-TKA | Follow-Up 14 mo Post-TKA | Change b | MCII |
|---|---|---|---|---|---|
| 30-s chair stand (reps) | 15 | 27 | 31 | 12c | 2–3 |
| Stair climb test (s) | 7.2 | 5.9 | 5.2 | −1.3 | −5.5 |
| 40-m fast walk (m/s) | 2.1 | 3.0 | 3.0 | 0.9c | 0.2–0.3 |
| 6-min walk (m) | 696 | 774 | 800 | 78c | 60 |
aMCII = minimal clinically important improvement; TKA = total knee arthroplasty.
bChange score from baseline to posttraining.
cChange score > MCII.
Alterations in Physical Functiona
| Functional Test | Baseline 6 mo Post-TKA | Posttraining 8 mo Post-TKA | Follow-Up 14 mo Post-TKA | Change b | MCII |
|---|---|---|---|---|---|
| 30-s chair stand (reps) | 15 | 27 | 31 | 12c | 2–3 |
| Stair climb test (s) | 7.2 | 5.9 | 5.2 | −1.3 | −5.5 |
| 40-m fast walk (m/s) | 2.1 | 3.0 | 3.0 | 0.9c | 0.2–0.3 |
| 6-min walk (m) | 696 | 774 | 800 | 78c | 60 |
| Functional Test | Baseline 6 mo Post-TKA | Posttraining 8 mo Post-TKA | Follow-Up 14 mo Post-TKA | Change b | MCII |
|---|---|---|---|---|---|
| 30-s chair stand (reps) | 15 | 27 | 31 | 12c | 2–3 |
| Stair climb test (s) | 7.2 | 5.9 | 5.2 | −1.3 | −5.5 |
| 40-m fast walk (m/s) | 2.1 | 3.0 | 3.0 | 0.9c | 0.2–0.3 |
| 6-min walk (m) | 696 | 774 | 800 | 78c | 60 |
aMCII = minimal clinically important improvement; TKA = total knee arthroplasty.
bChange score from baseline to posttraining.
cChange score > MCII.
Outcomes
Program Adherence
The patient completed 4 weeks of the program, took a 1-week break at Christmas, and finished the final 4 weeks. He completed all 40 total prescribed BFR exercise sessions. Muscle soreness associated with BFR exercise was low (0.0–1.4 cm). Joint pain persisted throughout the study (1.2–2.5 cm) but did not limit exercise and was generally lower after exercise (0.2–1.5 cm).
Alterations in Quadriceps and Physical Function
After training, lean leg mass and vastus lateralis thickness in the TKA leg increased by 4% and 14%, respectively (Fig. 2). Knee extensor strength increased by 55% (Fig. 2), and the patient reported less pain with the maximal contractions. Compared with baseline, posttraining strength symmetry increased from 64% to 98% of the uninvolved leg. Changes in physical function are reported in the Table. Most notably, the patient completed 12 more repetitions during the chair stand test, increased 40-m gait speed by 0.9 m/s, and improved the 6-minute walk test by 78 m. These change scores exceeded the minimal clinically important improvement values.21 After the program, the patient reported improved gait, enhanced stair climbing/descending ability, and achieved his goal of resuming his walking and cycling program. Quadriceps and physical function were generally well maintained at the long-term follow-up visit (6 months postintervention, 14 months post-TKA) (Fig. 2; Table).
(A) Alterations in lean leg mass, (B) vastus lateralis muscle thickness, and (C) knee extensor strength. TKA = total knee arthroplasty.
Role of the Funding Source
Blue Cross/Blue Shield of Michigan supported the authors’ research involving application of BFR exercise with clinical populations (ref. no. 002650.II). The funder played no role in the conduct or reporting of this case.
Discussion
Feasibility and Main Findings
Our patient was able to safely perform BFR exercise at home and tolerated the training well. To minimize the need for expensive equipment, we used body weight and walking exercises that required only the use of a thigh cuff and resistance band (~$30). We also accounted for BFR safety by using a moderate cuff pressure normalized to the patient’s limb occlusion pressure. The key outcomes were that 8 weeks of BFR exercise: (1) stimulated increases in lean leg mass and vastus lateralis thickness, (2) improved knee extensor strength, and (3) enhanced physical function. Thus, implementation of home-based BFR exercise was feasible, safe, and effective.
Quadriceps and Physical Function
Restoration of quadriceps size and strength is imperative for recovery of physical function following TKA.4 In this patient, lean leg mass and vastus lateralis thickness in the TKA leg increased considerably, which is noteworthy because at 6 to 12 months knee extensor strength is more associated with quadriceps size rather than quadriceps activation.22 Knee extensor strength in the TKA leg also increased dramatically with BFR exercise and reached 98% of the uninvolved leg. Meier and colleagues4 have reported that knee extensor strength generally increases up to 6 months postoperatively, tapers off to ~80% of the uninvolved leg, and sometimes does not fully recover. Thus, the level of knee extensor strength symmetry achieved by the patient was excellent because it surpassed TKA values documented in the literature4 and was within the range for middle-aged23 and older adults24 (≥90%) without osteoarthritis. As expected, muscle and strength gains translated to enhanced physical function as indicated by meaningful improvements in chair stand, 40-m fast walk, and 6-minute walk performance. Improvements in these functional tests were consistent with the patient’s self-reported increased walking, stair climbing, and cycling activity. Importantly, at the long-term follow-up visit the patient’s quadriceps size and strength were still generally well maintained and physical function was still high.
Possibility of BFR Exercise
Application of BFR exercise provides a stimulus for increasing muscle size and strength in healthy14 and clinical13 populations. To date, there is a single case series25 documenting BFR exercise use after TKA (3 patients). Gaunder’s team25 reported that BFR resistance exercise implemented at ~2.5 months postoperatively increased knee extensor strength by 57 to 360% and restored symmetry in all 3 patients. Our case report extends this by highlighting the possibility of home-based BFR use and a suite of BFR-induced changes in muscle size, strength, and physical function. Collectively, these 2 case reports suggest that BFR exercise has potential for accelerating recovery of quadriceps and physical function after TKA. The use of BFR with this population was also proposed in a review15 on TKA rehabilitation. Although BFR exercise prescription is not established for TKA, it seems that it could be used in the clinic or at home and through resistance, aerobic, or some combination of exercise modes. A next step is to investigate these possibilities through randomized controlled studies.
Limitations
It is important to point out that the patient was middle-aged and had a rather high level of physical function as indicated by his physical activity program and performance during the baseline functional tests. Thus, results may not be the same for older and/or less active adults with TKA. The patient also had significant osteoarthritis in his contralateral right knee, and thus muscle thickness and strength comparisons need be interpreted with caution. Further, although quadriceps size and strength contribute to improved physical function, there are additional factors that warrant consideration (eg, pain, quadriceps activation, hip strength). We also acknowledge that BFR exercise induces slight discomfort and dull pain at the site of the cuff that could affect patient motivation and compliance. Future work with this population should quantify the perceived level of discomfort during BFR exercise. Partial restriction of blood flow during exercise does have potential risks of inducing muscle soreness, adverse cardiovascular responses, blood clotting, and muscle/nerve damage. For this reason, its application presents a challenge.26 A systematic review and meta-analysis13 highlighted the use of BFR exercise in a range of clinical populations and adverse effects were rare.27 With careful consideration of past medical history, appropriate cuff pressure selection, close monitoring of training, and patient education, positive BFR exercise outcomes can be achieved safely.
Conclusion
An 8-week home-based program consisting of body weight and walking exercises with BFR increased lean leg mass, vastus lateralis thickness, knee extensor strength, and functional mobility in a patient who was 6 months post-TKA. To our knowledge, this is the first and only report to describe the use of BFR at home for a TKA patient who was discharged from physical therapy and to demonstrate a combination of structural and functional improvements. These results suggest that research is needed to determine the efficacy of using BFR exercise after TKA.
Author Contributions
Concept/idea/research design: M.A. Kilgas, A.E. Denherder, C.T. Williams, S.J. Elmer
Writing: M.A. Kilgas, A.E. Denherder, L.L.M. Lytle, C.T. Williams, S.J. Elmer
Data collection: M.A. Kilgas, A.E. Denherder, S.J. Elmer
Data analysis: M.A. Kilgas, A.E. Denherder, S.J. Elmer
Project management: S.J. Elmer
Providing participants: M.A. Kilgas
Consultation (including review of manuscript before submitting): M.A. Kilgas, A.E. Denherder, L.L.M. Lytle, C.T. Williams, S.J. Elmer
Ethics Approval
The experimental procedures described in this manuscript were approved by the Michigan Technological University Institutional Review Board, and the patient gave informed written consent.
Funding
Blue Cross/Blue Shield of Michigan supported the authors’ research involving application of BFR exercise with clinical populations (ref. no. 002650.II).
Disclosures
The authors completed the ICJME Form for Disclosure of Potential Conflicts of Interest and reported no conflicts of interest.
M.A. Kilgas, PhD, Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, Michigan.
A.E. Denherder, MS, Department of Kinesiology and Integrative Physiology, Michigan Technological University; and Department of Physical Therapy, Central Michigan University, Mt Pleasant, Michigan.
L.L.M. Lytle, PT, DPT, Department of Kinesiology and Integrative Physiology, Michigan Technological University; and Aspirus Keweenaw Outpatient Therapies, Calumet, Michigan.
C.T. Williams, PT, DPT, Department of Physical Therapy, Central Michigan University; and Department of Kinesiology and Integrative Physiology, Michigan Technological University.
S.J. Elmer, PhD, Department of Kinesiology and Integrative Physiology, Michigan Technological University, 1400 Townsend Dr, Houghton, MI 49931 (USA); and Department of Physical Therapy, Central Michigan University.
References
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