Quadriceps and hamstring strength and flexibility may decline immediately following total knee arthroplasty. Despite subsequent improvements over 1 year, deficits may persist.
In a prospective, longitudinal single-center study involving patients aged 50 to 80 years with primary, severe Kellgren-Lawrence grade 4 knee osteoarthritis who were scheduled for total knee arthroplasty, investigators compared strength and flexibility preoperatively and at 6 weeks, 3 months, 6 months, and 12 months postsurgery with age-, sex-, and body mass index–matched healthy controls.
Quadriceps and hamstring strength was evaluated with handheld dynamometry using 3 maximal voluntary contractions. The investigators evaluated hamstring flexibility by passive knee extension and quadriceps flexibility with a modified Thomas test. The patients underwent a standardized postoperative rehabilitation program that included progressive strengthening, mobility, stretching, functional training, balance training, and aerobic conditioning.
Among 134 patients assessed for eligibility, 77 were enrolled with follow-up completed by 77 patients at 6 weeks and 3 months, 54 at 6 months, and 26 at 12 months. The investigators reported no statistically significant baseline differences between patients who completed 12-month follow-up and those lost to follow-up. Longitudinal changes were evaluated using repeated-measures analysis of variance with available-case data, with Bonferroni correction applied to post hoc pairwise comparisons.
Mean quadriceps strength decreased from 12 lbs preoperatively to 7 lbs at 6 weeks, then increased to 30 lbs at 3 months, 38 lbs at 6 months, and 43 lbs at 12 months. Mean hamstring strength decreased from 20 lbs preoperatively to 13 lbs at 6 weeks before increasing to 30, 42, and 58 lbs, respectively. At 12 months, quadriceps and hamstring strength remained lower compared with control values of 75 and 68 lbs, respectively.
The investigators noted that attrition at 12 months may limit generalizability and that the absence of blinded outcome assessment may have introduced bias. They also noted that the analysis did not account for postoperative pain, differences in rehabilitation adherence, or physical activity, which could have affected the results.
“Despite substantial recovery, persistent quadriceps deficits at 12 months highlight the potential inadequacy of conventional rehabilitation programs in fully restoring muscle function,” wrote lead study author Saidan Shetty, of the Department of Anatomy at the Melaka Manipal Medical College at the Manipal Academy of Higher Education in India, and colleagues.
The study authors reported no conflicts of interest.
Source:Journal of Orthopaedics
