Effect of heat in increasing the range of knee motion after the development of a joint contracture: an experiment with an animal model.

OBJECTIVE

To compare the effects of 2 different heat modalities, infrared and ultrasonic therapy, on a knee flexion contracture.

DESIGN

In vivo, experimental, controlled study involving a rat knee joint contracture model that was immobilized using a ligature in flexion for 40 days.

SETTING

Collegiate research laboratory.

ANIMALS

Ninety-three adult male Wistar rats.

INTERVENTIONS

After remobilization, rats were assigned to 3 treatment groups: stretching only (S), stretching with infrared therapy (S+IR), and stretching with ultrasonic therapy (S+US). Six treatment sessions were given in 2 weeks.

MAIN OUTCOME MEASURES

The angle of maximum knee extension, wet-weight of triceps surae muscles, phase lag, and dynamic stiffness as mechanical responses were measured, and histologic study was conducted.

RESULTS

Compared with the S group, both the S+IR and S+US groups exhibited a significant increase in range of motion (ROM) (P=.021, P=.008, respectively) and a tendency to decrease the phase lag, but there was no significant difference between the 2 heat-combined groups. There were no differences in the weights of the triceps surae muscles and in dynamic stiffness among the groups.

CONCLUSIONS

Six treatment sessions of stretching with infrared or ultrasound were more effective than stretching without heat at increasing the ROM and decreasing the phase lag of a moderately severe joint contracture. The clinical implementation of heat is advocated to regain a normal ROM and mechanical property when experiencing a joint contracture.