1. Joseph W Fiske OMSIV – Touro University California; Shiley Center for Orthopaedic Research and Education at Scripps Clinic
2. John Ryan Quinn MD – Shiley Center for Orthopaedic Research and Education at Scripps Clinic
3. Eric T Owashi MD – Shiley Center for Orthopaedic Research and Education at Scripps Clinic
4. Julie C McCauley MPHc – Shiley Center for Orthopaedic Research and Education at Scripps Clinic
5. William D Bugbee MD – Shiley Center for Orthopaedic Research and Education at Scripps Clinic; Department of Orthopedic Surgery, Scripps Clinic
6. Steven N Copp MD – Shiley Center for Orthopaedic Research and Education at Scripps Clinic; Department of Orthopedic Surgery, Scripps Clinic
7. Kace A Ezzet MD – Shiley Center for Orthopaedic Research and Education at Scripps Clinic; Department of Orthopedic Surgery, Scripps Clinic
8. Adam S Rosen DO – Shiley Center for Orthopaedic Research and Education at Scripps Clinic; Department of Orthopedic Surgery, Scripps Clinic

Abstract

Introduction
Stiffness remains one of the most common indications for re-operation after total knee arthroplasty (TKA) and is a common reason for patient dissatisfaction. There is no study to our knowledge that evaluates if postoperative flexion is improved by showing patients an intraoperative photograph of their knee in maximum gravity assisted flexion following primary TKA.

Methods
Patients undergoing unilateral TKA were included; 85 patients received an intraoperative photograph of their knee in maximum gravity-assisted flexion (GAF) one day postoperatively and 79 patients did not receive an intraoperative photograph. GAF was measured preoperatively, intraoperatively pre-incision, intraoperatively post-surgery, 1 month postoperatively, and 4 months postoperatively. All patients had measurements obtained at each interval. Knee Society Score (2011KSS) and Knee Injury and Osteoarthritis Outcome Score, Joint Replacement (KOOSJR) were obtained preoperatively, 3 months postoperatively, and 1 year postoperatively.

Results
Mean age was higher in the photo group (72.1) than the no photo group (68.0, p=.001). Mean GAF preoperatively was 119.8° in the photo group and 118.4° in the no photo group (p=.484). Mean GAF intraoperatively pre-incision was higher in the photo group (124.9°) than the no photo group (120.5°, p=.009). Mean GAF intraoperatively post-surgery was higher in the photo group (125.5°) than the no photo group (121.0°, p=.001). Mean GAF 1 month postoperatively was lower in the photo group (110.0°) than the no photo group (114.6°, p=.016). Mean GAF 4 months postoperatively was lower in the photo group (117.4°) than the no photo group (122.1°, p=.001). There were no differences in KSS or KOOSJR scores. 

Conclusion
Despite age and intraoperative flexion possibly being confounding factors, patients shown an intraoperative photograph of their knee in maximum flexion failed to show greater knee flexion after TKA than patients not shown the photograph. Clinically, both groups had satisfactory outcomes after TKA with no differences in outcome scores.

Introduction
Total knee arthroplasty (TKA) is a successful intervention for patients with end-stage arthritis of the knee. TKA seeks to alleviate pain, correct deformity, and improve function, with range of motion being an important aspect of knee function. Patients require minimum degrees of knee flexion to perform specific activities of daily living (ADLs): 83° to climb stairs, 88-90° to descend stairs, and 115° to put on pants.(1-4) Range of motion (ROM) necessary for the majority of ADLs is commonly achieved and postoperative range of motion of between 100^o and 120^o has provided patient satisfaction.(5-7) Closer approximation of normal, native knee range of motion is likely to improve patient satisfaction. Considering 11-20% of patients are dissatisfied after TKA, commonly due to limitations in knee range of motion,(8-10) it is imperative to identify all factors that could help improve post-operative knee range of motion. Targeted ROM should be identified in the early post-operative period as flexion plateaus at three months and extension at 6 months.(11) 

Preoperative knee flexion (best predictor), surgical technique, prosthetic design, and rehabilitation are all factors that influence postoperative flexion.(12-14) Accordingly, goals to improve postoperative flexion have been established by surgeons and implant manufacturers alike. Stiffness is a common reason for patient dissatisfaction and remains the most common indication for re-operation after TKA.(9, 15) While treatment of TKA stiffness includes manipulations under anesthesia (MUA), arthroscopy, open arthrolysis, and revision surgery, management is best achieved by preventing its occurrence.(16) While there has been extensive research on methods to improve range of motion following TKA, there has been no study to date utilizing an intraoperative photograph to aid in patient range of motion. The purpose of this study is to evaluate if mean postoperative flexion at 1 and 4 months is greater in patients provided an intraoperative photograph of their knee in maximum gravity-assisted flexion after completion of primary TKA than patients not receiving a photograph. This study aims to provide a new tool for physicians to help explain to patients the amount of flexion that is attainable postoperatively in order to provide patients with a clear incentive to work toward a final flexion goal.

Methods
An institutional review board (IRB) approved prospective cohort study (level of evidence: II) was conducted. One hundred sixty-four patients undergoing a unilateral total knee arthroplasty (TKA) by one of three joint arthroplasty surgeons at our institution were included. Patients were enrolled in the study consecutively. The first group of patients (N=85) received an intraoperative photograph of their knee in maximum gravity-assisted flexion (GAF) 1 day postoperatively. The second group of patients (N=79) did not receive an intraoperative photo. Inclusion criteria consisted of: undergoing a unilateral TKA at our institution, all ages, and diagnosis of osteoarthritis. Exclusion criteria consisted of: history of prior surgery other than arthroscopy (osteotomy, ACL reconstruction, ORIF, etc.), bilateral TKA, pre-operative flexion of <75 degrees, patients with documented neurological deficit on the operative extremity, history of arthrofibrosis, any patient sustaining a complication delaying the ability to perform post-operative exercises/therapy, and varus/valgus deformity > 25 degrees. We did not exclude any patients based off of medical comorbidities although research has shown an increase in post-operative arthrofibrosis with specific medical conditions including diabetes mellitus, pulmonary disease, and depression.(17)

First phase: pre-operative 
Prior to surgery at a scheduled pre-operative history and physical appointment, all patients involved in the study were evaluated and gravity assisted knee flexion was measured using a goniometer. Gravity assisted flexion, shown in figure 1, was used since it is a more reproducible force compared to active or passive flexion. Landmarks for measurement were the greater trochanter (stationary arm), lateral epicondyle (axis), and lateral malleolus (moving arm). Photographs of the knee in gravity assisted flexion were taken and saved in the patient’s electronic medical records (EMR). Participants did not have access to the uploaded imaging on the EMR. At this time, 2011 Knee Society Scores (KSS) and Knee Injury and Osteoarthritis Outcome Scores, Joint Replacement (KOOSJR) were obtained.

Second phase: intra-operative 
Prior to beginning the surgery and under anesthesia, gravity assisted flexion was measured with a goniometer and documented in the operative report. After completion of the surgery with dressings on, gravity assisted flexion was again measured by goniometer and documented in the operative report. Photographs of the knee in gravity assisted flexion pre-incision and postoperatively were taken and uploaded in the EMR. Again, the images were not accessible to the patient. 

Third phase: inpatient hospitalization 
Patients were seen and discharged per typical protocol.  Patients randomly selected to receive the intra-operative photograph were provided a printout of the image on postoperative day 1 along with a note that stated: 

This is a photograph of your knee bent (flexed) after the surgery was completed. This picture is an incentive to show you how far you can bend your knee. It also lets you know that when you bend your knee and feel pain that you are not breaking anything inside or damaging your knee. Your goal should be to aim for obtaining the bend seen in your photo by six weeks.

Sincerely,

Your care team

All patients received the same instruction regarding their knee replacement and proceeded with the typical inpatient therapy/education and home therapy.  

Final phase: post-operative visits and time period 
Patients were seen at 1 and 4 months after surgery. At each visit, gravity assisted flexion was measured with a goniometer while supine using the same landmarks. Photographs of the knee in gravity assisted flexion were uploaded and flexion measurements were documented in the patient’s EMR. After all phases were completed, the data was assembled and evaluated. 2011 KSS and KOOSJR scores were obtained at 3 months and 1 year postoperatively. 

Data Analysis
An a priori power analysis was performed to determine the sample needed to test if the photo group and no photo group had an equivalent change in gravity assisted knee flexion (from preoperatively to the four-month visit). For the power analysis, we used historical data from our institution’s arthroplasty registry, which showed that primary unilateral TKA patients had a mean flexion of 118° and a standard deviation of 9.5° at their four-month follow-up. Using an effect of 5°, we determined that 58 patients would be required in each group. A two-tailed test was used with 80% power, α < 0.05, and 95% confidence. 

Means and frequencies were used to describe patient demographics and preoperative, intraoperative, and postoperative data. A 2-sided independent samples t-test was used to compare age, height, weight, and BMI between the photo and no photo group. A Pearson’s chi-square test was used to compare sex and side of TKA. A 2-sided independent samples t-test was used to compare preoperative, intraoperative, and postoperative data. Statistical significance was set at p < .05 and the minimum significant difference in degrees of flexion was set to 10°.

Results

Demographics
Out of 130 participants in the photo group and 100 participants in the no photo group, 85 and 79 participants respectively received gravity assisted flexion measurements at each interval—preoperative, intraoperative pre-incision, intraoperative post-surgery, 1 month postoperative, and 4 months postoperative. In the photo group, the mean age at the time of TKA was 72.1 ± 7.8 while the mean age in the no photo group was 68.0 ± 7.7 (p=.001). Forty-nine of 85 participants (57.6%) in the photo group and 44 of 79 participants (55.7%) in the no photo group were female (p=.752). The mean height was 66.5 ± 4.3 inches in the photo group and 66.9 ± 4.6 inches in the no photo group (p=.584). The mean weight was 178.1 ± 37.3 pounds in the photo group and 184.8 ± 43.5 in the no photo group (p=.288). The mean BMI was 27.9 ± 4.9 in the photo group and 29.0 ± 5.8 in the no photo group (p=.188). Forty-nine of 85 patients (57.6%) underwent right sided TKA in the photo group and 39 of 79 patients (49.4%) underwent right sided TKA in the no photo group (p=.259). Demographics are summarized in Table 1. 

Gravity Assisted Flexion Data
Preoperatively, mean gravity assisted flexion was 119.8° ± 13.2 in the photo group and 118.4° ± 12.1 in the no photo group (p=.484). Intraoperatively and pre-incision, mean gravity assisted flexion was 124.9° ± 9.7 in the photo group and 120.5° ± 11.7 in the no photo group (p=.009). Intraoperatively and post-surgery, mean gravity assisted flexion was 125.5° ± 8.1 in the photo group and 121.0° ± 8.7 in the no photo group (p=.001). 1 month postoperatively, mean gravity assisted flexion was 110.0° ± 12.8 in the photo group and 114.6° ± 10.8 in the no photo group (p=.016). 4 months postoperatively, mean gravity assisted flexion was 117.4° ± 10.0 in the photo group and 122.1° ± 8.4 in the no photo group (p=.001). Measurements of gravity assisted flexion at each interval are summarized in Table 2. 

When evaluating changes in gravity assisted flexion preoperatively to 1 month postoperatively, flexion decreased 9.7° ± 13.0 in the photo group and decreased 3.8° ± 12.8 in the no photo group (p=.004). From preoperatively to 4 months postoperatively, flexion decreased 2.4° ± 11.9 in the photo group while flexion increased 3.7° ± 11.5 in the no photo group (p=.001). From intraoperatively and pre-incision to 1 month postoperatively, flexion decreased 14.9° ± 13.9 in the photo group and decreased 6.0° ± 12.9 in the no photo group (p=.000). From intraoperatively and post-surgery to 1 month postoperatively, flexion decreased 15.4° ± 13.4 in the photo group and 6.4° ± 11.4 in the no photo group (p=.000). From intraoperatively and pre-incision to 4 months postoperatively, flexion decreased 7.6° ± 11.6 in the photo group and increased 1.6° ± 11.4 in the no photo group (p=.000). From intraoperatively and post-surgery to 4 months postoperatively, flexion decreased 8.1° ± 10.7 in the photo group and increased 1.2° ± 9.6 in the no photo group (p=.000). From 1 month to 4 months postoperatively, flexion increased 7.3° ± 10.4 in the photo group and increased 7.5° ± 10.2 in the no photo group (p=.910). Changes in gravity assisted flexion at different intervals are summarized in Table 3. 

Outcome Scores
Mean 2011 KSS scores were obtained preoperatively from 66 patients in the photo group and 63 patients in the no photo group (Symptom: 9.9 ± 5.1 in photo group, 8.5 ± 4.9 in no photo group, p=.107; Satisfaction: 14.9 ± 6.4 in photo group, 14.7 ± 7.8 in no photo group, p=.905; Expectation: 14.4 ± 1.0 in photo group, 14.2 ± 1.2 in no photo group, p=.228; Activity: 44.8 ± 16.1 in photo group, 42.3 ± 15.8 in no photo group, p=.369). Mean 2011 KSS scores were obtained from 67 patients in the photo group and 60 patients in the no photo group at 3 months (Symptom: 17.4 ± 4.9 in photo group, 18.2 ± 4.5 in no photo group, p=.343; Satisfaction: 25.3 ± 8.1 in photo group, 26.3 ± 8.3 in no photo group, p=.480; Expectation: 14.8 ± 7.5 in photo group, 13.6 ± 2.0 in no photo group, p=.205; Activity: 58.4 ± 16.8 in photo group, 62.1 ± 15.7 in no photo group, p=.205). Mean 2011 KSS scores were obtained from 48 patients in the photo group and 63 patients in the no photo group at 1 year. (Symptom: 20.8 ± 4.5 in photo group, 19.9 ± 4.8 in no photo group, p=.321; Satisfaction: 31.7 ± 7.6 in photo group, 30.6 ± 8.2 in no photo group, p=.479; Expectation: 14.1 ± 1.5 in photo group, 14.0 ± 3.8 in no photo group, p=.773; Activity: 73.6 ± 14.4 in photo group, 73.7 ± 16.1 in no photo group, p=.976). 

Mean KOOSJR scores were obtained preoperatively from 66 patients in the photo group and 60 patients in the no photo group (54.3 ± 12.0 in photo group, 52.3 ± 10.1 in no photo group, p=.324). Mean KOOSJR scores were obtained at 3 months from 65 patients in the photo group and 56 patients in the no photo group (63.0 ± 10.8 in photo group, 66.5 ± 12.2 in no photo group, p=.092). Mean KOOSJR scores were obtained at 1 year from 33 patients in the photo group and 52 patients in the no photo group (76.9 ± 13.8 in photo group, 75.1 ± 13.4 in no photo group, p=.549). Pre- and postoperative 2011 KSS and KOOSJR scores are summarized in Table 4. Of note, neither the photo group nor the no photo group had any patients requiring MUA.

Discussion
Stiffness is a common reason for patient dissatisfaction and remains one of the most common indications for re-operation after TKA.(9,16) If patients are unable to achieve 90° of flexion within 3 months after TKA, stiffness can be treated with MUA; however, patients are subject to complications related to the force used for manipulation which includes fracture or wound dehiscence.(18,19) Arthroscopy can provide increases in range of motion after TKA, but this adds the potential risks of an invasive procedure such as infection and component damage.(19) Open arthrolysis is another option, but has shown to provide inferior results compared to MUA and arthroscopy.(19) Nevertheless, the most effective management of stiffness after TKA is preventing its occurrence.(17)

The senior surgeon has been providing his patients with a postoperative photograph of the knee in maximum flexion as part of his normal protocol. After initiating this change in practice, he believed that postoperative range of motion was improved and patients’ complaints of stiffness diminished. In addition, many patients voiced that the photograph was a positive motivator for them in physical therapy. Based on this theory, we chose to perform a study with the other members of the group who were not currently using a postoperative flexion photograph to see if there was a statistical difference.

The senior surgeon typically performs the photograph in maximum flexion. We felt there could be some variability in different providers and the force they use to produce maximum flexion. Therefore, as part of the protocol we chose gravity assisted flexion as a more reproducible way of testing range of motion between surgeons and time points measured.

It was hypothesized that the photo group would have significantly greater gravity assisted knee flexion postoperatively; however, the data shows a higher degree of gravity assisted flexion in the no photo group (122.1°) than the photo group (117.4°). Although there was a statistically significant difference, both results clinically are satisfactory as patients rarely flex beyond 120° and postoperative range of motion between 100° to 120° has provided patient satisfaction.(5,6,7,20) While it was not initially a measured outcome in this study, it’s important to note that neither the photo group nor the no photo group had any patients requiring MUA. Additionally, there was no difference in 2011KSS or KOOSJR scores preoperatively or postoperatively.

There was a significant difference in gravity assisted flexion intraoperatively, with the photo group having a higher degree of flexion both pre-incision and post-surgery. Lee et al. is the only study to our knowledge that has specifically evaluated the relationship of intraoperative gravity assisted flexion to postoperative flexion and their data shows that 332 out of 364 patients obtained postoperative flexion within 5° of their measured intraoperative flexion.(21) The data from this study shows that on average, flexion in the photo group decreased 7.6° from intraoperatively pre-incision to 4 months postoperatively and decreased 8.1° intraoperatively post-surgery to 4 months postoperatively, which is inconsistent with the data from Lee at al.

There are several limitations to this study. Because the study began just prior to the initial peak of the COVID-19 pandemic, most patients lost to follow up were lost due to patients not wanting to be seen in office in order to maintain social distancing. This made it difficult to obtain follow up data in order to reach the 78 patients per group required to maintain the power of the study, despite starting with 130 patients in the photo group and 100 patients in the no photo group. However, a benefit of the photograph for all patients enrolled in this study was the ability to document the degree of knee flexion in the medical record following TKA.

Age was not an exclusion criterion, but there was a significant difference in age between the two groups with a mean age of 72.1 in the photo group versus 68.0 in the no photo group. Had a certain age range been retrospectively implemented as an exclusion criterion, the power of the study would not have been able to be maintained given the significant drop out caused by COVID-19. Additionally, social distancing due to COVID-19 likely prevented patients from receiving the appropriate physical therapy postoperatively.(22) This has a greater impact on older patients as they not only have a lower baseline muscle mass, but have an accelerated loss of muscle mass during periods of inactivity.(23,24) While multiple studies have shown that age does not have a direct significant impact on knee range of motion after TKA,(25-27) age could still be a confounding factor given that it wasn’t controlled for in this study impacted by the COVID-19 pandemic.

Other limitations may include the measurements which were recorded by the team caring for the patient at the time of the photograph. Having a number of reviewers who were blinded may have removed any variations in measurement technique.

This study did not address if patients did or did not enjoy the picture. We are unable to assess if the picture had a positive or negative effect on the psychological component of rehabilitation. The senior surgeon has noted that many patients in his practice voice that they like the photograph as a motivator. As we did not test this in our study, we cannot determine if the photograph adds to patient satisfaction.

Conclusion
Despite age and intraoperative flexion possibly being confounding factors, patients provided with an intraoperative photograph of their knee in maximum gravity assisted flexion failed to show greater knee flexion after TKA than patients not shown the photograph. Clinically, both groups had satisfactory outcomes after TKA with no differences in outcome scores and no patients requiring MUA. Further study may be warranted to see if closer follow-up and regular post-operative physical therapy visits could determine if this inexpensive, non-invasive tool is beneficial for patients after TKA.

Figure 1 | Figure 2 | Figure 3 | Figure 4 | Figure 5

References

1. Laubenthal KN, Smidt GL, Kettelkamp DB. A quantitative analysis of knee motion during activities of daily living. Phys Ther. 1972 Jan;52(1):34-43.
2. Andriacchi TP, Andersson GB, Fermier RW, Stern D, Galante JO. A study of lower-limb mechanics during stair-climbing. JBone Joint Surg Am. 1980 Jul;62(5):749-57.
3. Hyodo K, Masuda T, Aizawa J, Jinno T, Morita S. Hip, knee, and ankle kinematics during activities of daily living: a cross-sectional study. Braz J Phys Ther. 2017 May-Jun;21(3):159-166.
4. Scuderi GR. The stiff total knee arthroplasty: causality and solution. J Arthroplasty. 2005 Jun;20(4 Suppl 2):23-6.
5. Itokazu M, Uemura S, Aoki T, Takatsu T. Analysis of rising from a chair after total knee arthroplasty. Bull Hosp Jt Dis. 1998;57(2):88-92.
6. Padua R, Ceccarelli E, Bondì R, Campi A, Padua L. Range of motion correlates with patient perception of TKA outcome. Clin Orthop Relat Res. 2007 Jul;460:174-7. 
7. Rowe PJ, Myles CM, Nutton R. The effect of total knee arthroplasty on joint movement during functional activities and joint range of motion with particular regard to higher flexion users. J Orthop Surg (Hong Kong). 2005 Aug;13(2):131-8.
8. Bourne RB, Chesworth BM, Davis AM, Mahomed NN, Charron KD. Patient satisfaction after total knee arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res. 2010 Jan;468(1):57-63.
9. Jacobs CA, Christensen CP. Factors influencing patient satisfaction two to five years after primary total knee arthroplasty. J Arthroplasty. 2014 Jun;29(6):1189-91.
10. Noble PC, Gordon MJ, Weiss JM, Reddix RN, Conditt MA, Mathis KB. Does total knee replacement restore normal knee function? Clin Orthop Relat Res. 2005 Feb;(431):157-65.
11. Mutsuzaki H, Takeuchi R, Mataki Y, Wadano Y. Target range of motion for rehabilitation after total knee arthroplasty. J Rural Med. 2017 May;12(1):33-37.
12. Schiavone Panni A, Cerciello S, Vasso M, Tartarone M. Stiffness in total knee arthroplasty. J Orthop Traumatol. 2009 Sep;10(3):111-8.
13. Harvey IA, Barry K, Kirby SP, Johnson R, Elloy MA. Factors affecting the range of movement of total knee arthroplasty. J Bone Joint Surg Br. 1993 Nov;75(6):950-5.
14. Rodríguez-Merchán EC. The stiff total knee arthroplasty: causes, treatment modalities and results. EFORT Open Rev. 2019 Oct 7;4(10):602-610.
15. Abdel MP, Ledford CK, Kobic A, Taunton MJ, Hanssen AD. Contemporary failure aetiologies of the primary, posterior-stabilised total knee arthroplasty. Bone Joint J. 2017 May;99-B(5):647-652.
16. Merchán EC. The stiff total knee arthroplasty: causes, treatment modalities and results. EFORT Open Rev. 2019 Oct 7;4(10):602-610.
17. Fisher DA, Dierckman B, Watts MR, Davis K. Looks good but feels bad: factors that contribute to poor results after total knee arthroplasty. J Arthroplasty. 2007 Sep;22(6 Suppl 2):39-42.
18. Keating EM, Ritter MA, Harty LD, Haas G, Meding JB, Faris PM, Berend ME. Manipulation after total knee arthroplasty. J Bone Joint Surg Am. 2007 Feb;89(2):282-6.
19. Fitzsimmons SE, Vazquez EA, Bronson MJ. How to treat the stiff total knee arthroplasty?: a systematic review. Clin Orthop Relat Res. 2010 Apr;468(4):1096-106. 
20. Sultan PG, Most E, Schule S, Li G, Rubash HE. Optimizing flexion after total knee arthroplasty: advances in prosthetic design. Clin Orthop Relat Res. 2003 Nov;(416):167-73.
21. Lee DC, Kim DH, Scott RD, Suthers K. Intraoperative flexion against gravity as an indication of ultimate range of motion in individual cases after total knee arthroplasty. J Arthroplasty. 1998 Aug;13(5):500-3.
22. Pelicioni PHS, Lord SR. COVID-19 will severely impact older people’s lives, and in many more ways than you think! Braz J Phys Ther. 2020 Jul-Aug;24(4):293-294.
23. Miner AL, Lingard EA, Wright EA, Sledge CB, Katz JN; Kinemax Outcomes Group. Knee range of motion after total knee arthroplasty: how important is this as an outcome measure? J Arthroplasty. 2003 Apr;18(3):286-94.
24. Mitchell WK, Williams J, Atherton P, Larvin M, Lund J, Narici M. Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle and strength; a quantitative review. Front Physiol. 2012 Jul 11;3:260.
25. Gatha NM Clarke HD, Fuchs R, Scuderi GR, Insall JN. Factors affecting postoperative range of motion after total knee arthroplasty. J Knee Surg. 2004 Oct;17(4):196-202. 
26. Lizaur A, Marco L, Cebrian R. Preoperative factors influencing the range of movement after total knee arthroplasty for severe osteoarthritis. J Bone Joint Surg Br. 1997 Jul;79(4):626-9.
27. Bowden Davies KA, Pickles S, Sprung VS, et al. Reduced physical activity in young and older adults: metabolic and musculoskeletal implications. Ther Adv Endocrinol Metab. 2019 Nov 19;10:1-15

Required Disclosures and Declaration

• Copyright Information: No Copyright Information Added
• IRB Approval Information: Yes
• Disclosure Information: This study was supported by a grant from the Scripps Clinic Medical Group. There are no conflicts of interest for any of the authors.