Quadriceps/hamstrings co-activation increases early after total knee arthroplasty

Abstract

Quadriceps and hamstrings weakness and co-activation are present following total knee arthroplasty (TKA) and may impair functional performance. How surgery and post-operative rehabilitation influence muscle activation during walking early after surgery is unclear.

Purpose: Examine muscle strength and activation during walking before and one and 6-months post-TKA.

Methods: Ten patients (n=6 female; age: 64.7 ± 7.9 years; body mass index[BMI]:29.2 ± 2.5 kg/m(2)) and 10 healthy adults (n=6 female; age: 60.6 ± 7.4 years; BMI: 25.5 ± 4.0 kg/m(2)) participated. The patients underwent bilateral quadriceps and hamstrings strength testing and assessment of quadriceps/hamstrings co-activation and on/off timing using surface electromyography during a six-minute walk test (6MW). Groups, limbs, and changes with TKA surgery were compared.

Results: Patients reported greater 6MW knee pain pre- versus post-TKA and compared to controls (P<0.05). Patients had weaker surgical limb hamstrings (P<0.05) and bilateral quadriceps (P<0.05) strength than controls pre- and post-TKA. Before and 1-month post-TKA, patients had side-to-side differences in quadriceps and hamstrings strength (P<0.05). Controls walked farther than patients (P<0.01). Patients demonstrated greater surgical limb co-activation pre-operatively than controls (P<0.05). Co-activation was higher bilaterally one-month post-TKA compared to controls (P<0.05). Patients turned off their quadriceps later during stance than controls before and 1-month post-TKA (P<0.05).

Conclusions: Muscle strength, co-activation, and timing differed between patients and controls before and early after surgery. Rehabilitation to improve strength and muscle activation seems imperative to restore proper muscle firing patterns early after surgery.

Keywords: Muscle activity; Strength; Total knee replacement; Walking.

Figure 1

A–B. Muscle strength pre-operatively and at 1 and 6 months post-operatively for Quadriceps (A) and Hamstrings (B). The surgical limb is represented by black bars and the nonsurgical limb by white bars. Data are mean+standard error. *Indicates significant side-to-side difference in muscle strength. †Indicates significant difference from the control group bilaterally. ‡Indicates significant difference from the controls compared to the operative limb only.

Figure 2

Six minute walk distance (m). Black bars indicate values for TKA patients pre-operatively and at 1 and 6 months post-operatively. Gray bars indicate values for healthy adults. Data are mean+standard error. *Indicates patients walked significantly less distance than healthy adults.

Figure 3

Co-activation index for TKA patients (pre-operatively and 1 and 6 months postoperatively) and for healthy adults. The surgical limb is represented by black bars and the nonsurgical limb by white bars. Data are mean+standard error. *Indicates significantly greater co-activation in the surgical limb compared to healthy controls. †Indicates greater co-activation in the non-surgical limb compared to healthy controls.