Edited by: Maw Pin Tan, University of Malaya, Malaysia
Reviewed by: Glenn W. Stevenson, University of New England, USA; Lisa Robinson, Newcastle upon Tyne Hospitals NHS Foundation Trust, UK
Specialty section: This article was submitted to Geriatric Medicine, a section of the journal Frontiers in Medicine
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The patient was a 58-year-old African-American male with radiographic evidence of bilateral knee osteoarthritis (OA). He participated in a standardized 12-week eccentric strengthening program within a Veterans Affairs (VA) medical center.
The use of an eccentric training paradigm may prove to be beneficial for older adults with knee OA since eccentric muscle actions are involved in the energy absorption at the knee joint during gait and controlled movement during stair descent. Furthermore, in comparison to standard muscle actions, eccentric muscle actions result in higher torque generation and a lower rate of oxygen consumption at a given level of perceived exertion. Therefore, this mode of progressive resistance exercise may be ideal for older adults.
The patient completed an eccentric strengthening regimen for the knee flexors and extensors twice per week without an exacerbation of knee pain. Muscle morphology measures of the rectus femoris were measured using diagnostic ultrasound. Isokinetic measures of muscle peak torque were obtained at 60°/s and 180°/s. Functional performance was assessed using a physical performance battery and stair-step performance was assessed from the linear displacement of the center of gravity trajectories obtained with a force plate. Visual analog scale pain ratings and self-reported global disease status were also documented. Post-exercise assessments revealed improvements in sonographic muscle size and tissue composition estimates, peak knee extensor torque (ranging from 60 to 253%), functional performance, and global disease status.
The patient exhibited improvements in muscle morphology, muscle strength, functional performance, pain, and global disease status after 12 weeks of an eccentric strengthening regimen. The intervention and outcomes featured in this case were feasible to implement within a VA medical center and merit further investigation.
Given the increased average life expectancy due to advancements in technology and medical care, chronic conditions such as osteoarthritis (OA) may have an impact on the aging population regarding their performance of daily tasks and health-related quality of life (HRQL). OA is the most prevalent form of OA (
Physical therapy is the conservative approach for addressing the sequalae associated with knee OA, and progressive resistive exercise along with manual therapy techniques to improve joint arthrokinematics are often employed within the plan of care. While investigators have noted that physical therapy features effective intervention approaches for knee OA, it is important to note that these interventions do not only entail exercise (
The benefits of strength training for knee OA has been studied extensively over the past two decades (
This study was approved by the Institutional Review Board of the Research & Development Service at the Washington DC Veterans Affairs (VA) Medical Center and informed consent was obtained from the patient. The patient featured in this case report was a 58-year-old male veteran with a history of chronic left knee pain over the course of the past 4–5 years. His primary complaints included knee joint stiffness, soreness, with intermittent swelling. The patient stated that he engaged in limited physical activity, with sporadic bouts of formal exercise approximately “1–2 times every few weeks.” However, he worked in an office, which required manual labor that would vary from 20 to 40% of his total hours. The patient reported that his biggest challenge was negotiating stairs, with the worst exacerbation of pain occurring while descending stairs. He also had difficulty with standing up after sitting down for periods longer than an hour, and pain with walking after 5–10 min. The patient participated in physical therapy for the knee pain approximately 2 years prior, and reported that the rehabilitation regimen was very effective in the management of his knee OA. However, following his discharge from physical therapy, he noted that his left knee pain had gradually returned after 4–5 months. The patient stated that he was not involved in any formal exercise program or receiving any physical therapy care at the time of his evaluation.
Left knee pain was rated as 6 out of 10 using a standard numeric pain scale at the time of the initial examination. The patient had no complaints of any problems with the right knee joint. An antalgic gait favoring the left knee was noticeable upon visual gait assessment and observation. Left knee flexion active range of motion (AROM) was found to be 120° and extension AROM to be 0°. Physical appearance of the knees was characterized by normal alignment with no notable excessive valgus or varus positioning. No swelling or edema was present upon visual inspection. There was notable crepitus with passive ROM into flexion and extension that was noticeable by both the patient and clinician. No hypersensitivity or tenderness was elicited with palpation at the joint line. There was some reported discomfort with tibial internal and external rotation at 90° of knee flexion. Special tests were performed to rule out any meniscal or ligamentous sources of pain or dysfunction. Apley’s and McMurray’s tests were both found to be negative for meniscal injury. Valgus and varus stress tests were negative, indicating no issues with the medial collateral and lateral collateral ligaments, respectively. Clarke’s test for chondromalacia patella was positive. The only notable manual muscle test (
All strength assessment and eccentric PRE was performed using an isokinetic dynamometer (Biodex System 4, Biodex Medical Systems, Shirley, NY, USA). The eccentric PRE regimen was 12 weeks in duration with training scheduled twice per week with at least 1 day of rest between sessions. The progression of the eccentric PRE workload was adapted from our previously described method of isokinetic eccentric-only strengthening exercise (
The progression phase features a training algorithm that allows for the modification of the training workload each session. This modification may result in exercise intensity remaining stable between sessions, or increasing by 5% if all torque targets are met (across all PRE sets), or decreasing by 10% if the torque targets are not met due to excessive fatigue (i.e., attainment of ≤70% of the target exercise torque during any PRE set). All exercise sets included 10 repetitions with the exercise volume progressing from three to four sets by Week 6, and the progressive phase movement speed transitioning from 60°/s to 90°/s by Week 10. The completion of each set was proceeded by 1 min of recovery time. The patient was able to monitor his ability to meet the torque targets with each repetition by viewing the torque-time curves on the Biodex computer monitor during the exercise bouts. Given our interest integrating eccentric PRE into the plan of care for patient populations with significant impairments, we have elected to refrain from maximally testing eccentric strength in people who are naïve to the training stimulus and/or managing active musculoskeletal or neuromuscular disease. Consequently, the isokinetic concentric maximum voluntary contraction (MVC) at 60°/s was used to derive the estimated eccentric peak torque. This estimate was obtained using the following equation (where, MVC expressed as torque, Ecc = eccentric, and Con60 = concentric at 60°/s):
This equation includes a minor adjustment of the previously used co-factor of 1.4 since its initial use did not include patients with joint pain (
Outcome measures featured in this report were utilized at Week 1 and 12 of the eccentric PRE regimen, and included multiple domains of disablement. Pain was documented using a written, self-reported, visual analog scale (VAS) based on a numeric scale of measurement (VAS; 0–10 scoring range) (
The patient’s ability to ascend and descend a step was objectively assessed using the Neurocom® Step Up and Over test (Neurocom International, Clackamas, OR, USA). This test involves starting in stance using a standardized location on a force plate, ascending an 8-inch high step with the ipsilateral limb, transitioning from step ascent to step descent while advancing the trailing contralateral limb, and then ending the test when both feet have returned to the force plate. This test documents elements of performance such as movement time and center of gravity (COG) displacement based on three consecutive trials for each leg. Mean values for movement time were obtained from the Neurocom® EquiTest software, and the mean linear COG displacement trajectories were measured using ImageJ (NIH, Bethesda, MD, USA; Ver. 1.48) to determine the maximum distance traversed during the Step Up and Over test. While the Neurocom® Step Up and Over test has been featured in previous validity studies (
The Knee Injury and Osteoarthritis Outcome Score (KOOS) was selected as an outcome measure for OA disease status and HRQL. The construct validity (
The patient completed all of the training sessions without any exacerbation of pain during or after the exercise bouts. The exercise sessions lasted approximately 20–30 min. The exercise target torques (i.e., the torque goal for each 10-repetition set) for the knee extensors at the start of the progressive phase (Week 4) were 54 ft-lbs on the less involved limb (right side) and 32 ft-lbs on the more involved limb (left side). At the end of the progressive phase (Week 12) the patient advanced his exercise target torques to 112 ft-lbs on the less involved limb and 76 ft-lbs on the more involved limb. These final torque targets during the eccentric PRE for the less involved and more involved limbs were 107 and 138%, respectively, higher than the pre-exercise isokinetic concentric MVC for the knee extensors. All of the pre and post-exercise isokinetic MVC values are summarized in Figure
Performance of the Step Up and Over test also reflected potential differences between the lower extremities. The linear displacement of the COG trajectory on the less involved limb was 1.11 m at the start of the exercise regimen and 1.14 m at Week 12. In comparison, the more involved limb exhibited linear displacement COG trajectory values that increased from 1.02 to 1.16 m over the 12-week period. As a result, the asymmetry in the Step Up and Over test performance decreased from 8.8 to 1.7%. The task performance time was similar between the lower extremities pre and post-exercise with the less and more involved limbs attaining 1.83 ± 0.05 s and 1.86 ± 0.26 s mean values, respectively, at Week 12. However, the longest duration single trial task performance time was observed during Week 12 in the more involved limb (2.10 s for the left leg versus 1.87 s for the right leg). The COG trajectories are shown in Figure
The patient’s general physical performance was observed using the PPT-7 test battery. He demonstrated modest improvements as his score increased from 19 during Week 1 to 21 during Week 12. Gait speed was also examined independently from the other PPT-7 items to further characterize the patient’s physical status. Habitual walking speed is a widely recognized as a key functional measure and an indicator of health status in older adults (
All of the KOOS subscale post-exercise values were improved in comparison to the baseline values. The pre and post-exercise scores are presented in Table
KOOS subscales | Week 1 | Week 12 | MDC/MPCI |
---|---|---|---|
Pain | 42 | 50 | −/+ |
Symptoms | 57 | 64 | −/− |
ADL | 40 | 50 | −/+ |
Sport/Recreation | 5 | 40 | +/+ |
QOL | 0 | 38 | +/+ |
The patient exhibited post-exercise increases in all of the KOOS subscales. However, the improvements met the criteria of the MDC and PMCI only in the Sport/Recreation and QOL subscales.
ADL, activities of daily living; QOL, quality of life; MDC, minimal detectable change values: Pain, 13.4; Symptoms, 15.5; ADL, 15.4; Sport/Rec, 19.6; QOL 21.1; MPCI, minimal perceptible clinical improvement: ≥8.
The progression of knee OA is characterized by a group of symptoms that may include joint pain, lower extremity weakness, gait disturbances, and a general loss of endurance secondary to the activity limiting pain (
An important observation from this case study is the ability of a patient with significant knee pain (VAS = 6 out of 10 at the start of the program) to engage in an eccentric PRE regimen without any exacerbation of his symptoms. Moreover, the patient did not report any DOMS despite the general concerns about excessive muscle damage secondary to eccentric exercise for specific musculoskeletal conditions (
The patient appeared to have a meaningful response to the eccentric PRE stimulus given the magnitude of change reflected in the post-exercise MVC values. However, it is important to note that the age of the patient featured in this report was 58 years old, which is younger than the median age of U.S. veterans (62 years of age) and outside the NIH National Institute of Aging’s category of the “young-old” (65–80 years of age) (
Since eccentric PRE was used as the sole strength training regimen for the patient during the intervention period, the strength assessment measures at Week 12 may represent the transference of eccentric muscle action adaptations to concentric muscle actions. While the specificity of training applies to all forms of muscle action, the transference of the physiologic adaptations to eccentric exercise to isometric or concentric muscle actions have been previously noted (
The specificity of the eccentric PRE regimen may confer an advantage to people with knee OA since difficulty in descending a curb or a flight of stairs is a common patient complaint (
The patient appeared to have a favorable response to eccentric PRE based on his self-assessment of OA disease status and HRQL (Figure
The patient featured in this report appeared to have positive physiological adaptations to eccentric strength training without an exacerbation of his knee OA symptoms. His apparent improvement in knee extensor muscle size, tissue quality, and strength may have influenced his improved post-exercise status concerning functional performance and self-reported disease status and HRQL. All case reports constitute a detailed account of clinical practice, and cannot be used to establish causal relationships between interventions and patient outcomes. In addition, patients with significant comorbid factors and advanced age may have a differential response to the eccentric PRE stimulus described in this report. Nevertheless, this report served as a proof-as-concept endeavor that demonstrated the safe application of the eccentric PRE in a veteran with symptomatic and radiographic evidence of bilateral knee OA.
Continued investigation of the efficacy of eccentric PRE for older adults with knee OA may be merited. Additional pilot studies and observational trials will be needed to better understand the patient response to eccentric PRE based on estimates of OA severity and levels of patient disability. Further inquiry concerning exercise adherence in supervised and non-supervised settings would also aid the adoption of formalized PRE regimens in the management of knee OA. In general, traditional isoinertial strengthening approaches (i.e., exercise with an emphasis on concentric muscle actions) are more readily adaptable for home exercise programs in comparison to the eccentric training paradigm. Consequently, developmental work may be needed to refine eccentric PRE regimens for home use by patients with a wide range of physical abilities.
Regarding the outcome measures featured in this report, the use of diagnostic musculoskeletal ultrasound provided important information about post-exercise changes in muscle tissue morphology and had a low patient and practitioner burden. Moreover, the novel approach used in this report to objectively assess step ascent/descent performance using the Neurocom® Step Up and Over test appeared to reveal differences between the more involved and less involved limb. However, more study will be needed to understand the clinical and research utility of this assessment method for people with knee OA. Finally, the KOOS questionnaire was a valuable tool in the clinical management of the patient. The QOL subscale may prove to be useful as a primary outcome measure in this patient population, and the multidimensional Pain scale may offer some advantages over the use of simple VAS ratings of pain related to knee OA.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Funding for this project was provided by the VA Office of Academic Affiliations (OAA; 38 U.S.C 7406) and the VA Office of Research and Development, and by the National Center for Advancing Translational Sciences, National Institutes of Health (NIH), through the Clinical and Translational Science Awards Program (CTSA grant # UL1TR000101). Any opinions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Veterans Affairs or the U.S. Department of Health and Human Services.