Promoting Physical Activity Via Physical Therapist Following Knee Replacement- The PATH Study
Phase: NA
Conditions: Knee Arthroplasty
Sponsor: University of South Carolina

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1) Study Title:
Promoting Physical Activity via Physical Therapist Following Knee 
Replacement – The PATH Study 
Principal Investigator: 
Christine Pellegrini, PhD 
cpellegrini@sc.edu 
803-777-0911
Co-Investigators: 
Debbie Brown, MS, PT, OMT-C 
Sara Wilcox, PhD 
Study Site:  
Palmetto Health – USC Orthopedic Center 
Palmetto Health USC Orthopedic Center phone number: 
803-296-9207
Funding:  
University of South Carolina ASPIRE-I 
NCT: 
NCT03768206 
Date: 
3/17/2020 

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2) Background / Justification For Study 
More than 4 million adults over the age of 50 years are living with a total knee 
replacement (TKR).1 TKR utilization in the US continues to dramatically increase across 
all ages, with over 615,000 TKR completed annually.2 The number of new TKR’s is 
expected to approach 3.48 million by 2030.3 TKR substantially increases lifetime medical 
costs and accounts for 61% of osteoarthritis-related direct medical costs.4 Hospital-based 
costs of TKR exceed $16 billion.5 With the dramatic expected rise of TKR utilization 
over the next 20 years3 and substantial burden on the economy, it is imperative to identify 
approaches to maximize the benefits of the costly treatment.   
TKR is effective at improving health-related quality of life,6 pain,7 and physical 
function8 with more than 75% of patients experiencing improvements.9 Despite the 
improvements in preoperative symptoms, corresponding post-operative changes in 
physical activity are not typically observed, with physical activity levels at 1 year after 
surgery remaining similar to pre-operative levels.10,11 Less than 5% of patients reach 
recommended physical activity guidelines after knee replacement.12,13 The continued low 
levels of physical activity are concerning because inactivity is associated with increased 
risk of mortality14 and chronic disease,15,16 as well as lower quality of life17 and poorer 
physical function.18,19 Even though improvements are observed in pain and function, it is 
unknown why patients continue to maintain their pre-operative low levels of physical 
activity.   
Following TKR, patients receive physical therapy either at home or at a skilled 
nursing rehabilitation facility and then transition to outpatient rehabilitation for 4-6 
weeks.20 The primary objective of therapy is to help the patient regain strength and 
mobility after surgery by strength and mobility exercises and functional training.21 
Improved function is reported by 70-80% of patients and decreased pain is reported by 
85-90% of patients receiving physical therapy.22 While physical therapists are effective at 
enhancing function and strength outcomes via rehabilitation exercises following TKR, 
encouraging patients to engage in the recommended 150 minutes/week of moderate-to-
vigorous intensity physical activity during and after therapy is outside of their focus and 
not typically discussed.13  
To date, only a few studies have focused on increasing overall physical activity levels 
in TKR patients; however, the increases in activity observed have been modest compared 
to changes observed in non-TKR populations and interventions were costly or resource 
intensive.23-25 Due to the high volume of contact time outpatient physical therapists have 
with TKR patients (2-3 times/week for 4-6 weeks) and the sense of rapport that is 
established between the therapist and patient,21 physical therapists may be a promising 
avenue to deliver a physical activity intervention. Given the success of physical therapists 
to achieve patient strength, mobility, and range of motion goals following TKR, it is 
likely that they could help patients increase their overall physical activity levels. TKR 
requires rehabilitation; thus, having physical therapists deliver a physical activity 
intervention during the required rehabilitation is a novel and efficient approach to reach 
patients and promote physical activity. This research is significant because it is the first 
step towards building a progressive line of research targeting the development of a low-
additional cost and translatable physical activity intervention that will have the ability to 

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be widely disseminated by physical therapists providing rehabilitation, both in home or 
outpatient, to TKR patients.  
Preliminary Studies: 
The PACE study (AHRQ K12HS023011) compared weight loss programs that started 
either before knee replacement (PACE) or started 12 weeks after surgery (Delayed 
PACE). Sixteen patients were randomized (63.3±7.5 years old, 69% female, 69% White, 
BMI of 36.5 ± 5.1 kg/m2) to PACE or Delayed PACE. Primary outcomes from 11 
participants were objectively assessed at 26 weeks after surgery. Nine participants 
provided self-reported outcomes at approximately 12.78±1.5 months after knee 
replacement. Participants in Delayed PACE lost significantly more weight (-7.6±5.9kg, -
7.9±5.9%) than PACE (-2.5±2.7kg, -2.6± 2.6%) at 26 weeks (P=0.03). Delayed PACE 
maintained greater weight loss outcomes than participants in PACE at one year post-
operatively. Pain intensity decreased (P<0.001) and function improved (P=0.001) 
significantly, but no significant changes were observed in physical activity (Table 1). 
Table 1. Physical Activity Pre- and Post-Surgery in PACE (n=6) & Delayed PACE (n=7) 
 
Baseline 
12 Weeks 
26 Weeks 
Bouted MVPA,  
min/week 
    PACE 
   Delayed PACE 
 
 
81.2±141.8 
37.6±85.7 
 
 
3.5±5.4 
62.1±135.8 
 
 
33.3±76.4 
78.1±108.0 
Steps/day 
    PACE 
    Delayed PACE 
 
5715.7±3098.0 
6062.4±2817.6 
 
4255.6±1687.8 
4943.6±1653.2 
 
4991.8±2910.2 
6324.4±2201.3 
 
The research team has experience with recruitment of TKR patients in the Columbia, 
SC area. Currently, we have recruited 12 patients who underwent a TKR to participate in 
an ongoing study examining the use of Fitbits and social support on physical activity over 
a 4-month period. To date, 73% of patients recruited for this study are from the 
Columbia, SC region. Additionally, across the 5 orthopedic surgeons within the Palmetto 
Health USC Orthopedic Center, an average of 21.8 TKR are completed each week.  
 
3) Objectives / Research Aims 
The purpose of this proposed project is to conduct a pilot randomized controlled trial 
to examine the feasibility and preliminary efficacy of a physical therapist led physical 
activity intervention on physical activity levels in TKR patients after surgery. The 
specific aims of the project are: 
 
Aim 1: To examine the feasibility and acceptability of conducting a randomized 
controlled trial examining a physical therapist led physical activity intervention for 
TKR patients within an outpatient physical therapy facility. Specifically, enrollment, 
retention, session attendance and duration, treatment fidelity, and patient and physical 
therapist satisfaction will be examined.  
 

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Aim 2: To examine the effect of a physical therapist led physical activity intervention 
on the changes in physical activity, physical function, and pain in TKR patients.  
4) Setting 
The study procedures will be performed at Palmetto Health USC Orthopedic Centers.  
Potential patients will be identified and recruited after they attend their first physical 
therapy appointment by physical therapists participating in the study. Patients who are 
interested in participating will complete the informed consent process with the Principal 
Investigator or study research assistants.  Study data and consent forms will be stored in a 
locked office at Palmetto Health USC Orthopedic Centers and the University of South 
Carolina Technology Center to Promote Healthy Lifestyles.  
5) Resources Available 
The purpose of this study is to examine the feasibility of conducting a physical therapist 
led physical activity intervention in a clinical setting. We will strive to recruit a total of 
50 patients.  If recruitment efforts are slow, we will plan to recruit additional physical 
therapists to participate in the study and assist with recruitment over the 15 month 
granted funded period of time.  
Dr. Christine Pellegrini, the Principal Investigator and Assistant Professor in the 
Department of Exercise Science at USC, will oversee all study related procedures, 
included but not limited to recruitment, behavioral intervention, and data collection and 
analysis. Dr. Pellegrini has extensive experience overseeing behavioral clinical trials.  
Debbie Brown, Co-Investigator and Senior Physical Therapist, will help recruit patients 
at Palmetto Health USC Orthopedic Centers and will coach participants as part of the 
intervention during standard physical therapy appointments.  
Dr. Sara Wilcox, Co-Investigator and Clinical Psychologist, will serve as the mentor to 
Dr. Christine Pellegrini as well as oversee delivery and treatment fidelity of the 
behavioral intervention. Additionally, Dr. Wilcox serves as a PI for another study through 
Palmetto Health (Pro00033131 Promoting Health in Pregnancy and Postpartum).  
All members of the study team will have a copy of the study protocol and know their 
respective research duties. 
6) Prior Approvals 
NA 
7) Study Design 
a. Recruitment Methods 
Patients will be recruited from Palmetto Health USC Orthopedic Center. After 
completing the first outpatient physical therapy appointment, potentially eligible patients 

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identified by Palmetto Health Physical Therapists will be provided information about the 
study verbally by a USC research staff member. Interested patients will be able to ask 
questions and read the consent form. They will have the opportunity to complete the 
informed consent process either at the first or second outpatient physical therapy 
appointment.     
 
b. Inclusion and Exclusion Criteria                                                                                                
 
After initial identification of potential patient participants by physical therapists, 
research staff will screen patients for eligibility criteria in-person or over the telephone.  
 
Inclusion criteria: 
 Eligible participants will 1) be 40-79 years of age, 2) have had a knee replacement in  
the last 2 months, 3) be willing to wear an accelerometer for 7 days during  
assessments, and 4) be English  
speaking.   
Exclusion criteria:  
As all patients will be under physicians’ supervision post-TKR, participants will only 
be excluded if they (1) have any contraindications to activity, (2) have a mobility 
limiting comorbidity (e.g. spinal stenosis), or (3) have a scheduled surgery (i.e., TKR 
on contralateral knee) within the next 6 months. 
c. Local Number of Subjects 
We will aim to randomize 50 patients that had a knee replacement within the last 2 
months and are attending outpatient physical therapy at the Palmetto Health USC 
Orthopedic Center.  We anticipate that we will need to approach and screen 
approximately 75 patients to enroll our goal of 50 patients.  
d. Study-Wide Number of Subjects 
NA 
e. Study Timelines 
Subject participation will last 12 weeks. We estimate it will take 15 months to 
complete the study, which will include finished study enrollment, data collection and 
data analysis (See Figure 1).  
 

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f. Study Endpoints 
Assessments will be completed before the second outpatient therapy session 
(baseline) and at 12 weeks after TKR. Detailed descriptions and a timeline of 
outcomes are provided below in the text and Table 2. Briefly, at both 
assessments, participants will be asked to complete surveys (demographics, brief 
medical history, KOOS, PROMIS, self-identification), which should take 
approximately 20 minutes to complete. Based on participant preferences, surveys will 
be able to be completed on paper or online via RedCAP, with the exception of the 
PROMIS surveys which are computer adaptive surveys. Participants will also be 
given an Actigraph Link accelerometer and ActivPAL monitor to wear for 7 days at 
each assessment. These monitors will be provided at the in-person assessment or 
mailed to the participants. At the end of the 7 days, these monitors will be returned to 
the PT clinic or participants will be provided with a prepaid padded envelope to 
return the monitor. Only at 12 weeks will participants complete functional tests and 
the Surgery and Medication Questionnaire, which will take approximately 15 minutes 
to complete. In the event participants are unable to complete the function tests at the 
in-person assessment, we will ask participants to complete the chair stand test at 
home and self-report the outcomes. Participants will not be asked to complete the 6-
minute walk or timed up and go at home. Participants will receive $20 for completing 
the 12-week assessment.  
Table 2. Data Collection  
Measure  
Baseline  
12 Weeks  
Participant Demographics  
X  
  
Participant height and weight 
X 
X 
Brief Medical History  
X  
X  
Knee Injury and Osteoarthritis Outcome Score (KOOS)  
X  
X  
PROMIS Pain Intensity, Pain Interference, & Mobility   
X  
X  
WOMAC Pain and Stiffness  
X  
X  
Physical Function  
   6-minute walk  
  Timed up and go  
  Chair stands  
  
  
 
X 
X  
X  
Physical activity (Actigraph)  
X  
X  
Sedentary time (ActivPAL)  
X  
X  
Self-Reported Exercise Identity  
X  
X  
PATH Study Survey  
  
X  
 
Primary Outcomes: The feasibility and acceptability of conducting a randomized 
controlled trial within an outpatient physical therapy setting is the primary endpoint.  
Specifically, we will examine the number of participants enrolled vs. approached, 
participant retention, number of therapy sessions attended, session duration, and 
treatment fidelity. Further, participants will complete a PATH Study Survey at the 12 
week assessment. Physical therapists will complete a brief evaluation about delivering the 
PATH program.   

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Secondary Outcomes:   
• 
Physical activity will be measured using Actigraph Link accelerometers owned by 
the TecHealth Center at the University of South Carolina. During assessments, 
participants will be asked to wear the Actigraph on their waist for 7 days. Non-wear 
time will be defined as ≥90 minutes with zero activity counts, allowing for up to 2 
minutes of <100 counts/min.26 Physical activity will be categorized as light (100-
2019 counts/min) and moderate-to-vigorous (MVPA) (≥2020 counts/min).27 Total 
MVPA over the week will be calculated. Steps/day will also be obtained. A valid day 
will be considered if participants wore the accelerometer for at least 10 hours/day. 
Participants will also be asked to complete a log indicating times the accelerometer 
was worn and taken off over the 7-day assessment period.  
• 
Sedentary time will be measured using ActivPALTM (PAL Technologies Ltd, 
Glasgow, UK), a small lightweight (15 g) uni-axial accelerometer. The time spent 
sitting/lying, standing, and walking, transitions and step counts will be 
determined. The ActivPAL summarizes data in 15 second intervals over 24 hours at a 
sampling frequency of 10 Hz.28 During assessments, participants will be asked to 
wear the ActivPAL on their thigh for 7 days. Participants will also be asked to 
complete a log indicating times the ActivPAL was worn and taken off over the 7-day 
assessment period.    
• 
Physical function measures will include the chair stand, timed up and go, and 6-
minute walk test. All physical function tests will be completed following 
Osteoarthritis Research Society International (OARSI) recommendation 
procedures.29 During the chair stand test, patients are asked to complete as many chair 
stand repetitions as possible during a 30-second period. The Timed Up and Go Test 
assesses the time in seconds taken to rise from a chair, walk 3-meters, turn, walk back 
to the chair, and sit down. The Six Minute Walk Test evaluates the maximal distance 
a patient can cover during a 6-minute period.   
• 
Patient-Reported Outcomes will be assessed using two methods: 1) Patient-
Reported Outcomes Measurement Information System (PROMIS)30 utilizes a 
computer adaptive test via RedCap.31 We will assess pain intensity, pain interference, 
and mobility; 2) Western Ontario and McMaster Universities Arthritis Index 
(WOMAC) is a 15-item survey assessing pain and stiffness over the last 48-hourse on 
a 5-point Likert scale.32   
• 
Self-reported exercise identity will be assessed at baseline and 12-week 
assessments using the Self-Reported Exercise Identity Scale.33 Participants will rate 
on a scale from 1 (strongly disagree) to 5 (strongly agree) their feelings relating to 
exercise identity. Examples include, “I would feel a real loss if I were forced to give 
up exercising” and “I need exercise to feel good about myself.”   
 

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g. Procedures Involved 
Design Overview: We propose to conduct a pilot two-arm cluster randomized controlled 
trial with patients attending outpatient physical therapy following TKR. The proposed 
project was developed in collaboration with Debbie Brown, Senior Physical Therapist at 
Palmetto Health USC Orthopedic Center. Over 9 months, TKR patients (n=50) attending 
outpatient physical therapy at Palmetto Health USC Orthopedic Center will be recruited 
and randomized to either 1) PATH-12 (control), or 2) PATH. Due to potential 
contamination of the intervention between patients in PATH-12 and PATH during typical 
open, group-like physical therapy settings, we have opted to randomize physical therapy 
sites instead of individual patients.  Specifically, physical therapy sites will be 
randomized to either Immediate or Delayed. The first phase of the study will take place 
starting in November and end after 25 participants have been recruited.  During this time, 
those sites randomized to Immediate will receive the PATH intervention and those sites 
randomized to Delayed will receive the PATH-12 intervention.  There will then be a 
“wash out period” to allow for all the participants to finish their current PT.  After this 
“wash out period”, the second phase of the study will begin and will end after 25 
participants have been recruited.  During this time, those sites randomized to Immediate 
will receive the PATH-12 intervention and those sites randomized to Delayed will 
receive the PATH intervention.”   
Screening: Participants will be required to complete a brief screening after the first 
physical therapy appointment. Research staff will administer the screening in-person or 
over the telephone. The screening will assess eligibility criteria and willingness to 
participate. Following the completion of the screener, eligible and interested participants 
will be invited to complete the informed consent process.   
 
Randomized Conditions:  
PATH-12 (control). Patients randomized to receive PATH-12 will undergo the standard 
physical therapy following TKR. The study will not change any treatment patients 
typically receive and instead will just document how long sessions occur and if any 
aerobic activity goals were set.  In addition to the standard physical therapy received and 
to enhance retention in the study, all participants who receive PATH-12 will be given a 
brief physical activity coaching session led by a trained USC research staff member at 12 
weeks following the completion of the assessment. Participants will receive all materials 

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provided to PATH and the session is expected to last approximately 1 hour. In the event 
this cannot be completed in-person, it will be completed over the telephone. 
 
PATH. Patients randomized to receive PATH will undergo the standard physical therapy 
following TKR.  In addition, physical therapists will briefly discuss lifestyle and 
moderate-to-vigorous physical intensity activity at each session. At least once/week, 
physical therapists will help patients set a SMART (Specific, measurable, attainable, 
realistic, timely) goal related to overall aerobic physical activity and identify strategies 
that will help them achieve their goal. Physical therapists will use motivational 
interviewing techniques and check in on patients’ progress towards goals at each session.  
Physical therapists will be encouraged to engage in physical activity coaching and goal 
setting during down time while patients are completing aerobic warm up, rehabilitation 
exercises, or during ice, manual therapy, neuromuscular electrical stimulation, or scar 
management to ensure these discussions do not add additional time to the regular therapy 
session.  
 
Intervention Data Collection.  Physical therapists for both randomized conditions will 
document the session start and end times as well as any goals that are set during the 
sessions. Physical therapists can document the session information on a paper form  
 
Treatment Fidelity. Due to the open, group-like nature of physical therapy and patient 
confidentiality, we are unable to audio record treatment sessions. Therefore, to monitor 
treatment fidelity to ensure intended session content for both conditions is delivered and 
that unintended session content (i.e., contamination such as goal setting on physical 
activity levels with a patient randomized to PATH-12) is not delivered, physical 
therapists will complete a session checklist. In addition, random observations will occur 
by USC research staff.  The physical therapist and observation fidelity checklists will 
monitor session duration, goals set, and indication if aerobic physical activity was 
discussed.    
 
h. Data and Specimen Banking 
NA 
i. Statistical Analysis 
Descriptive statistics will be used to describe baseline characteristics, establish 
recruitment and retention rates, and examine intervention intensity (session frequency, 
duration, and fidelity) and patient and therapist satisfaction. Mixed ANOVA or 
ANCOVAs, if appropriate adjustments are required based on baseline characteristics, will 
examine the changes in physical activity levels (MVPA/week, steps/day), and pain 
(PROMIS and WOMAC) across time between PATH and PATH-12. Additionally, 
differences between PATH and PATH-12 in physical function (chair stands, Timed Up 
and Go, 6-minute walk) will be examined at 12 weeks. Although the proposed study may 
not be powered to detect significant differences, the results will allow us to collect 
feasibility and acceptability data, refine the intervention, if necessary, and determine 
effect sizes for future grant submissions.    

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j. Data Management  
All surveys will be administered either on paper or online via REDCap (secure, web 
application for building and managing online surveys and databases – managed by the 
University of South Carolina). Paper surveys will be stored in a locked filing cabinet at 
Palmetto Health-USC Orthopedic Center or the TecHealth Center at University of South 
Carolina. All computer files will be password protected. Only the study team will have 
access to the data.  
k. Confidentiality 
A number will be assigned to the participant who agrees to be a part of the study. This 
number will be used on the project records rather than their name, and no one other than 
the study team will be able to link the data with the name. Study records/data will be 
stored in locked filing cabinets and protected computer files at Palmetto Health USC 
Orthopedic Center and the University of South Carolina’s TecHealth Center.    
 
l. Provisions to Monitor the Data to Ensure the Safety of 
Subjects 
Patient enrollment numbers, consent documents, the data collection sheet and any 
reportable events will be monitored by the Study Coordinator every month.  
 
Any issues found will be rectified as appropriate and preventative actions, as 
needed, will be taken in efforts to eliminate the issue in the future.  
 
m. Withdrawal of Subjects 
Participants will be informed they can leave the research at any time without penalty. If a 
participant decides to withdraw, no more information will be collected. The participants 
will be made aware of this during the consent process.   
  
Any data collected during their participation may be used by the investigators for the 
purposes described above. Choosing not to be in the study will not result in any penalty 
or loss of benefit to which participants are entitled. Specifically, the choice not to be in 
this study will not negatively affect a participant’s right to any present of future medical 
treatment or his/her present or future employment.   
 
8) Risks to Subjects 
The risks of participating in this study are minimal. Participants may experience:   
1. Feelings of muscle soreness and fatigue during physical function tests or engaging 
in physical activity. Although participants will be experiencing muscle soreness 
and fatigue from the surgery, we will attempt to minimize any additional 
symptoms.  Participants will be allowed to take breaks at any time during function 

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tests and the physical activity goals will be tailored specifically based on the 
participants progress after surgery. The physical therapist will work with the 
participant to ensure a safe and reasonable goal is set to minimize additional 
symptoms following surgery. Participants will be encouraged to stop engaging in 
physical activity immediately if at any time they are injured or are encouraged to 
stop engaging in physical activity from their physical therapist/physician/medical 
professional.   
2. Skin irritation from wearing the physical activity monitors.  Participants will be 
asked to wear two physical activity monitors, one on their waist, and one on their 
thigh for 7 days. The waist-worn monitor will only be worn during waking hours 
to minimize discomfort. The ActivPAL will be securely taped with water proof 
sealing on the participants thigh and be worn 24 hours for 7 days. In the event the 
participant experiences discomfort, the participant will be asked to remove the 
tape. Participants will be provided with additional tape and asked to reapply the 
monitor once the skin irritation resolves.   
9) Potential Benefits to Subjects 
Participants may or may not experience any benefits from participating in this study. 
If participants modify activity behaviors, they may be experience positive changes to 
health and mood.  Additionally, this research will help us understand if a physical 
therapist led physical activity intervention can help to increase activity after knee 
replacement.    
10) 
Provisions to Protect the Privacy Interests of Subjects 
The research study will be explained to potential subjects in a private manner. 
Consenting will be done also in a private room, away from other subjects or Palmetto 
staff. Participants will have the option to not answer any question that they do not feel 
comfortable answering.  
11) 
Compensation for Research-Related Injury 
NA 
12) 
Economic Burden to Subjects 
NA 
13) 
Consent Process 
Informed consent will be obtained either after the first outpatient physical therapy 
appointment or before the second appointment by a USC research team member. Full 
details of the study will be discussed, and participants will be reminded that 
participation is voluntary. Disclosure will be made of the nature and potential risks of 
participating and all participants will be asked if they have any questions about their 

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participation to ensure they understand the procedures. We estimate it will take 
approximately 15 minutes to complete the consent process. The paper consent form 
has been developed according to the requirements of Palmetto Health 
and the University of South Carolina Institutional Review Boards. Additionally, the 
consent process with each participant will be documented on the informed consent 
checklist. A copy of all signed IRB-approved consent forms will be provided to the 
participant.   
14) 
Process to Document Consent in Writing 
Interested participants will provide written informed consent on an informed consent 
document approved by the IRB. Date, time, and the research staff member obtaining 
consent will be documented for each participant.   
15) 
Vulnerable Populations 
NA  
16) 
Drugs or Devices 
NA 
17) 
Multi-Site Research 
NA 
18) 
Community-Based Participatory Research 
NA 
19) 
Sharing of Results with Subjects 
At the end of the trial, a results presentation will be given for interested participants. If 
participants are unable to attend, the presentation will be provided via email or letter. 
20)      Bibliographic References 
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Weinstein AM, Rome BN, Reichmann WM, et al. Estimating the burden of total 
knee replacement in the United States. The Journal of bone and joint surgery 
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2. 
Losina E, Thornhill TS, Rome BN, Wright J, Katz JN. The Dramatic Increase in 
Total Knee Replacement Utilization Rates in the United States Cannot Be Fully 
Explained by Growth in Population Size and the Obesity Epidemic. The Journal 
of bone and joint surgery American volume. 2012;94(3):201-207. 

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3. 
Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of Primary and 
Revision Hip and Knee Arthroplasty in the United States from 2005 to 2030. The 
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Dunlop DD, Song J, Semanik PA, Sharma L, Chang RW. Physical activity levels 
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Dunlop DD, Semanik P, Song J, et al. Moving to Maintain Function in Knee 
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