Osteoarthritis (OA), caused by the break­down of joint car­ti­lage, leaves more than 20 mil­lion people in the United States suf­fering from recur­ring pain and frus­trated over their lim­i­ta­tions in move­ment. But phys­ical therapy and mechan­ical and indus­trial engi­neering researchers at North­eastern Uni­ver­sity have broken new ground with an inter­dis­ci­pli­nary study of fac­tors that cause and exac­er­bate OA.

To explore these factors—including body weight and knee-​​joint abnor­mal­i­ties such as frontal knee alignment—the study required subject-​​specific knee-​​joint analyses. Researchers found that these indi­vid­u­al­ized assess­ments from 3-​​D imaging, along with ear­lier diag­nosis based on a patient’s knee align­ment, are crit­ical fac­tors in dra­mat­i­cally improving treat­ment and pre­ven­tion. Their research, which was recently fea­tured on the cover of the Journal of Ortho­pedic Research, advances Northeastern’s research mis­sion to solve global chal­lenges, with a focus on health, secu­rity, and sustainability.

A recent North­eastern grad­uate, Nicholas Yang, spear­headed this research as the basis for his PhD thesis in mechan­ical engi­neering. Yang was the paper’s lead author, joined by three coau­thors: pro­fessor Hamid Nayeb-​​Hashemi and assis­tant pro­fessor Ashkan Vaziri—both in the Depart­ment of Mechan­ical and Indus­trial Engineering—and Assis­tant Pro­fessor of Phys­ical Therapy Paul Canavan.

It’s ground­breaking because we’re inte­grating the bio­me­chanics, phys­ical therapy, gait analysis and the engi­neering,” Canavan said.

Not only can we see if someone is more at-​​risk, but we can apply this subject-​​specific model for inter­ven­tions in the future,” Nayeb-​​Hashemi said.

Researchers said sharing their exper­tise in human anatomy and cal­cu­lating force dis­tri­b­u­tion was inte­gral to the collaboration.

The project was very inter­esting and chal­lenging, because I had to learn how the human body works so I could apply engi­neering prin­ci­ples to answer bio­me­chan­ical research ques­tions,” Yang said.

The knee is one area where osteoarthritis, the most common form of arthritis, can develop. The research indi­cated that people with irreg­ular knee align­ment — either varus (bow-​​legged) align­ment or valgus (knock-​​kneed) align­ment — are more sus­cep­tible to devel­oping this condition.

North­eastern stu­dents vol­un­teered for the study, which required them to walk on a plat­form that mea­sured applied force to the knee while high-​​speed motion analysis cam­eras cap­tured their move­ments. This data was fed into soft­ware to build 3-​​D models of each student’s knee joints, allowing researchers to mea­sure indi­vid­u­al­ized stress levels on the knee cartilage.

Given that the geom­etry of knee joints varies from person to person, researchers said their method­ology more accu­rately gauges strain and stress dis­tri­b­u­tion to the knee joint when com­pared to past studies that have used gen­er­al­ized assess­ments. As a result, pre­ven­ta­tive mea­sures such as cus­tomized shoe inserts, strength­ening of spe­cific leg mus­cles or weight loss, can be tai­lored to each person.

This (subject-​​specific method) is some­thing that makes our research unique,” Vaziri said.