In the last 20 years, the demand for total knee replacements has risen and is expected to continue rising. This increase in demand can be attributed to the increased diagnosis of osteoarthritis, increased rate of recovery after surgery, and better surgical techniques utilized by surgeons. The objective of this study was to determine the influence of body mass index (BMI) on the time for total knee replacement rehabilitation in an outpatient setting. Information including gender, height, weight, age, and range of motion (ROM) at evaluation and discharge was obtained for 26 patients from two physical therapy clinics. ROM was a measure of success in this study with a successful total knee replacement rehabilitation achieving 0-110º ± 5 in flexion and extension. Age, gender and BMI were analyzed to determine their role in total knee replacement rehabilitation time. Age was found to have an inverse relationship, with the elderly patients gaining full range of motion quicker than the younger patients (p=0.046), but there was no apparent relationship between gender and rehabilitation time (p=0.530). BMI did play a role in rehabilitation time, with higher BMI’s requiring more time for total rehabilitation (p=0.044). As BMI is one of the few characteristics that is modifiable prior to surgery, this influence of BMI on total knee replacement rehabilitation time is significant. A more successful rehabilitation could occur if surgeons informed patients that a reduction in weight would greatly improve their chances for rehabilitation success.
Hometown: Johnson City, Tenn.
Senior Study Title: “The Role of Body Mass Index (BMI) on Total Knee Replacement Rehabilitation”
Advisor: Dr. Drew Crain
For three years, biology major Shelley Clark ’11 dreaded the start of her Senior Study. Stories of all-night writing sessions and lab experiments gone awry told by upperclassmen had led her to believe that the graduation requirement was a year-long, painful headache.
Now a Maryville College graduate who will start physical therapy school at East Tennessee State University next month, Clark looks back on the two-semester, required project with appreciation.
It not only helped her get in to the physical therapy school, it earned her a graduate assistantship within the physical therapy department. Soon after she begins her studies, she’ll likely be conducting research alongside a professor.
“My thesis was the main thing that qualified me for the position,” she said. “The majority of my admissions interview was talking about my research and how I could continue it and where I had presented.
“I believe that the Senior Study also showed them that I had done a lot of observation in the field and knew what I was getting into,” she added.
Clark’s Senior Study, entitled “The Role of Body Mass Index (BMI) on Total Knee Replacement Rehabilitation,” was inspired by shadowing a physical therapist and seeing that most of the therapy was for total knee replacements.
Dr. Drew Crain, professor of biology and Clark’s advisor for the study, helped her focus the research.
“Shelley approached me about doing her Senior Study in the area of physical therapy, because she wants to be a PT,” Crain remembered. “At first, she didn't have any idea what to do, but after conversations and review of the literature, we uncovered an interesting question – ‘What influence does BMI have on recovery time after knee replacement surgery?’”
The 44-page thesis includes in-depth explanations of osteoarthritis, procedures for replacing a knee and different types of post-operative rehabilitation and what research has shown regarding rehabilitation strategies and their impact on range of motion.
The meat of Clark’s manuscript, however, is the data gathered and analyzed from 26 patients from two physical therapy clinics, Blount Memorial Outpatient Rehabilitation and Total Rehabilitation-Cherokee.
“The objective of this study was to determine the influence of BMI on the time for total knee replacement rehabilitation in an outpatient setting,” she explained.
In addition to weight and height, Clark obtained information on each patient’s gender, age and range of motion at evaluation and discharge. She also collected data on whether or not the patients used a walking aid.
The data – collecting it and analyzing it – was the most challenging part of the study, she said.
“There are so many restrictions placed on patient information, and I needed to know age, sex, BMI, range of motion at evaluation and discharge, as well as the amount of time they were in therapy,” she explained. “This is where I really need to thank the physical therapists who gave me the data. I really couldn't have done this study without their help.”
Crain said students often underestimate the realities of data collection, but said that Clark was thorough and persistent. Her exceptional process for gathering relevant information and analyzing it were reasons he recommended her study for the library’s permanent collection.
“Shelley learned patience from this project,” he said. “She also gained knowledge about appropriate statistical analysis of data and how important statistical analyses are to interpreting the data that is collected. Her data set was quite impressive, which also makes it cumbersome; however, her data were made manageable by some fairly simple statistical analyses.”
Looking at BMI, Clark grouped the patients into four categories: Normal, Overweight, Obese and Very Obese.
The data showed that patients with lower body mass were rehabilitated in significantly shorter periods of time. While that didn’t come as a big surprise to her, it did surprise her that, according to the data, older patients recovered more quickly than younger patients.
“This was opposite of what I had expected, so I talked to some physical therapists whom I knew, and they told me that by the time the older patients have the replacement, the pain that they feel during rehabilitation is actually less that what they were feeling before.”
Crain, whose expertise is in amphibians and reptiles, said he learned much from Clark’s study.
“I am always asking myself ‘How can this animal be used to model the human condition?’ and Shelley’s thesis opened my eyes to a new area of study.”
Clark said professors at ETSU have encouraged her to continue the research with a wider patient base. She’ll likely have ample opportunity to do that. Her plan is to earn her doctorate in physical therapy (DPT), work in the field for a couple of years and then return to school for a Ph.D. so that she can teach.
“This idea [for the Ph.D.] actually came up at my interview with ETSU,” Clark explained. “I was talking with three professors about my research, and they asked me if I wanted to do research as a career. I told them that I really enjoyed research but also looked forward to clinic time. They suggested that I look into teaching because I can teach classes, have clinic time and do research. This seems like the perfect combination for me because I had also thought about teaching after doing supplemental instruction for cellular biology during my sophomore and junior years at MC.”
As a teacher, she’ll undoubtedly model Crain’s approach to student advising.
“Dr. Crain was the best thesis advisor I could have asked for,” she said. “He was so encouraging and good at giving advice and helping me figure out next steps when I got to the ‘Where do I go from here?’ stage. He kept me directed and focused.
“Even after the study was completed, Dr. Crain continued to push me by having me apply to present at the Blue Ridge Undergraduate Research Symposium.”
Crain is currently using Clark’s research as an example for other Maryville College students.
“Shelley Clark did an excellent job from start to finish,” the professor said. “She will be an exceptional physical therapist in a few years, and I’m glad she got a jump start on her career through our undergraduate research program.”