Shock! Age has MINIMAL Effect on Knee Kinematics!?

In work from Australia, researchers sought to deepen our understanding of the relationship between knee kinematics and age.

Their work, “Age has a minimal effect on knee kinematics: A cross-sectional 3D/2D image-registration study of kneeling,” appears in the August 16, 2019 edition of The Knee.

Jennie Scarvell, Ph.D., with the Trauma and Orthopaedic Research Unit at the University of Canberra and co-author explained the key questions that prompted this new study to OTW, “We have seen that ‘good’ knee kinematics are difficult to replicate with total knee replacement. We asked whether this might be because we have been aiming for implants to replicate young healthy knee kinematics, but we haven’t really considered if we should really be trying to replicate kinematics for age-relevant knees.”

“There is very little research available for kinematics of knees at age 69, the mean age for total knee replacement. So, we asked what healthy aging knee kinematics might look like. We wanted to get the most accurate picture possible of healthy older knees, to compare the kinematics profiles.”

“We looked at kneeling, as it is a difficult activity for people with knee osteoarthritis, at the extreme of flexion, but kneeling is culturally important for many communities. This work is part of a larger study that looks at knee motion (kinematics) as it applies to healthy aging, osteoarthritis and total knee replacement.”

The research team selected 67 individuals with healthy knees (age range 20-90) and then categorized them into four 20-year age groups. The team then employed 3D/2D registration of CT and fluoroscopy during kneeling to capture 3D knee kinematics.

The research team then compared kinematic variables of position, displacement, and rate-of-change in six-degrees-of-freedom for each of the age cohorts while also controlling for University of California Los Angeles activity scale and the Assessment of Quality of Life physical scores.

Dr. Scarvell summarized the team’s outcomes to OTW, “The most important finding is that age had minimal impact on knee kinematics, even for the extreme flexion of kneeling.”

“We found that only above the age of 80 years were there any differences, and these differences were seen when we compared the 20 to 80+ age groups. We found some loss of posterior femoral translation in deep flexion and some more valgus in the knees of older people.”

“It looks like there might be less femoral external rotation with flexion, but this was not significant. Our method of capturing kinematics using fluoroscopy registered to CT is highly accurate and sensitive, so we were surprised not to see very much change in the kinematics in the older knees.”

“This finding challenges the notion that age is an independent risk factor for osteoarthritis in knees.”

“For the 60 to 79 years age group, the kinematics were very similar to younger age groups. This could mean that it is not necessary to design implants for an age-relevant knee. It might be that osteoarthritis has far greater impact on knee kinematics than age has. But that is a story for another day.”

“Age has less impact on knee kinematics than we supposed. If a person is showing altered kinematics for example in their gait, or ability to kneel, it is unlikely to be due to age.”