Objectives:
Posterior Cruciate Ligament (PCL) injuries occur isolated or in combination with knee dislocations. PCL injuries can be treated surgically or with progressive exercises in combination with a support brace. However, larger prospective studies reporting outcome of exercise-related treatment are lacking.
The aim was to investigate changes in patient-reported and muscular strength outcome of a physiotherapy-led progressive exercise program plus a support brace in patients with an acute injury of the PCL over a 24-months follow-up. Furthermore, to report conversion to surgical reconstruction.

Methods

In the period from June 2015 to January 2017, 50 patients with an acute injury of the PCL were consecutively enrolled in a prospective case-series study. The patients were treated with a support brace the first 12 weeks and furthermore underwent a 16-week physiotherapy-led progressive exercise program including strength, stability and coordination training. PCL lesions were diagnosed by magnetic resonance imaging and tibial offset using the posterior drawer test. Changes in patient-reported outcome was investigated with the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) from baseline (diagnosis given) to 1 and 2 years follow-up. Changes in isometric knee flexion and extension strength was measured with a static strength force gauge from 16 weeks to 1 year after initiating the exercise program. Finally, conversion to surgical treatment was determined.

Results

The IKDC-SKF score increased statistically significantly from 35 (SD 9.7) points at baseline to 62 (SD 15) points after 2 years. Isometric knee flexion strength of the injured knee increased statistically significantly from 0.93 (SD 0.36) Nm/kg to 1.1 (SD 0.36) Nm/kg, corresponding to an increase of 16%. In contrast, isometric knee extension of the injured knee did not change from 16 weeks to 1 year (0.10 (-0.022-0.21) Nm/kg, p=0.107). The isometric knee flexion strength of the healthy knee was 1.1 (SD 0.47) Nm/kg at 16 weeks and 1.2 (SD 0.47) Nm/kg at 1 year, while isometric knee extension of the healthy knee was 1.8 (0.52) Nm/kg at 16 weeks and 1.8 (0.50) at 1 year Nm/kg. In the study period, seven patients (14 %) converted to PCL reconstruction resulting in 43 patients for 1-year follow-up that completed the combined brace and rehabilitation treatment. Of the patients converting to reconstruction, two patients had an isolated ligament injury and five patients had dislocation of the knee.

Conclusions

Treatment with progressive exercises in combination with a support brace after acute PCL injury demonstrated clinically relevant improvements in patient-reported outcome after one and two years and an improvement of 16% in flexion strength from 16 weeks to 1 year. Furthermore, treatment with progressive exercises in combination with a support brace resulted in a 14% conversion rate to surgical treatment due to continued instability. Consequently, clinically relevant improvements in subjective outcome and strength and a low surgical conversion rate after the progressive exercise program can be expected with the exercise/brace treatment concept for PCL injury.