Predictors of knee extensor muscle strength one year after total knee arthroplasty – a prospective longitudinal study

Per Sjöström, Lena Nordeman, Ola Rolfson, Anette Larsson
Purpose:

To examine predictors of knee extensor muscle strength one year after TKA.

Methods:

A prospective longitudinal observational study was conducted among patients 65 years or older schedules for TKA. Measurements were made in a primary care setting 0-2 weeks before and one year after TKA. Knee extensor muscle strength was measured as absolute maximal voluntary contraction (AMVIC) using a make-test with a fixated hand-held Micro Fet 2 Dynamometer (Hoggan Scientific, Salt Lake City, UT, USA). Relative maximal voluntary isometric contraction (RMVIC) was calculated as body weight/AMVIC. Multivariable regression was used to analyse potential preoperative predictors of the affected side for AMVIC and RMVIC one year postoperative as well ΔAMVIC and ΔRMVIC from preoperative (0-2 weeks before TKA) to one year after TKA. Potential predictors analysed were preoperative AMVIC, RMVIC, Limb Symmetry Index (LSI) of AMVIC, 30 s Chair Stand Test (30CST), 6-Minute Walk Test (6MWT), walking aid (yes or no), and subscales of Knee Injury and Osteoarthritis Outcome Score (KOOS).  Final models were adjusted for age, gender, and Body Mass Index (BMI).

Results:

40 participants completed one-year postoperative follow-up, age range 65-85 years, 38% (n=15) were female. Statistically significant predictors (p 0.05) of AMVIC at one-year follow-up in our preliminary analysis were gender, BMI, 6MWT, walking aid and AMVIC affected side at first assessment. Adjusted r2= .878 for overall model. Statistically significant predictors (p 0.05) of RMVIC at the one-year follow-up in our preliminary analysis were KOOS-activities of daily living, KOOS-quality of life, 6MWT and RMVIC affected side at preoperative assessment. Adjusted r2= .763 for overall model. 

Conclusion(s):

Our preliminary findings suggest that greater preoperative physical capacity, specifically knee extensor muscle strength and performance on the 6-minute walk test (6MWT), are significant predictors of improved postoperative knee extensor muscle strength. 

Implications:

Preliminary results indicate that patients and caregivers should be informed that preoperative physical capacity (6MWT, AMVIC and RMVIC) predicts better knee extensor muscle strength following TKA. This supports the recommendation of exercise to enhance postoperative functional outcome for people with knee osteoarthritis.

Funding acknowledgements:
Research and Development Council of Södra Älvsborg, Region Västra Götaland, Sweden.
Keywords:
Total knee arthroplasty
Knee extensor muscle strength
Primary Care
Primary topic:
Orthopaedics
Second topic:
Musculoskeletal: lower limb
Third topic:
Primary health care
Did this work require ethics approval?:
Yes
Name the institution and ethics committee that approved your work:
The study was reviewed and approved by the Swedish Ethical Review Authority.
Provide the ethics approval number:
No 2021-03590 and No 2024-04643-02
Has any of this material been/due to be published or presented at another national or international conference prior to the World Physiotherapy Congress 2025?:
No

Back to the listing