Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty

Abstract

Background/rationale: Although TKA reliably reduces pain from knee osteoarthritis, full recovery of muscle strength and physical function to normal levels is rare. We presumed that a better understanding of acute changes in hamstrings and quadriceps muscle performance would allow us to enhance early rehabilitation after TKA and improve long-term function.

Questions/purposes: The purposes of this study were to (1) evaluate postoperative quadriceps and hamstrings muscle strength loss after TKA and subsequent recovery using the nonoperative legs and healthy control legs for comparison, and (2) measure hamstrings coactivation before and after TKA during a maximal isometric quadriceps muscle contraction and compare with nonoperative and healthy control legs.

Methods: We prospectively followed 30 patients undergoing TKA at 2 weeks preoperatively and 1, 3, and 6 months postoperatively and compared patient outcomes with a cross-sectional cohort of 15 healthy older adults. Bilateral, isometric strength of the quadriceps and hamstrings was assessed along with EMG measures of hamstrings coactivation during a maximal isometric quadriceps contraction.

Results: There were no differences in strength loss or recovery between the quadriceps and hamstrings muscles of the operative leg throughout the followup, although differences existed when compared with nonoperative and healthy control legs. Hamstrings muscle coactivation in the operative leg during a maximal quadriceps effort was elevated at 1 month (144.5%) compared to the nonoperative leg.

Conclusions: Although quadriceps dysfunction after TKA typically is recognized and addressed in postoperative therapy protocols, hamstrings dysfunction also is present and should be addressed.

Clinical relevance: Quadriceps and hamstrings muscle strengthening should be the focus of future rehabilitation programs to optimize muscle function and long-term outcomes.

Fig. 1

The percentage change in quadriceps and hamstrings strength in the operative leg after TKA is shown. There were no differences in strength loss or recovery between the quadriceps (dark gray) and hamstrings (light gray) muscles during the first 6 months after TKA (mean ± SE of the mean [SEM]). Statistical analyses were performed on raw strength (N-m)/body weight (kg) values, not percentage change from preoperative levels.

Fig. 2A–B

Strength with time for the operative, nonoperative, and healthy control (A) quadriceps and (B) hamstrings are shown. Quadriceps strength in the operative leg (A) was significantly less than for the nonoperative and healthy legs preoperatively and 6 months after TKA. Hamstrings strength in the operative leg (B) was significantly less than for healthy legs, preoperatively and 6 months after TKA, yet was not significantly different from nonoperative legs at either time. Strength (N-m) is normalized to body weight (kg) (mean ± SEM).

Fig. 3

Hamstrings EMG coactivation across time is shown. The coactivation index was defined as (peak hamstrings EMG during quadriceps maximal voluntary isometric contraction [MVIC]/peak hamstrings EMG during hamstrings MVIC). One month after TKA, hamstrings coactivation in the operative leg was significantly elevated compared with that of the nonoperative leg with a similar trend for comparisons with healthy control subjects.