Summary

Any post-operative restriction following ACLR can limit both knee extension and flexion recovery during the early phase of rehabilitation.

Abstract

Purpose

Previous research has demonstrated that 3% of patients have range of motion (ROM) loss after primary Anterior Cruciate Ligament Reconstruction (ACLR). Early gains in ROM post ACLR are critical for full recovery of mobility. Lack of full knee extension by 6 weeks increased the incidence of cyclops syndrome by 8-fold and loss of total knee motion by greater than 50°, compared to the uninvolved side, by 8 weeks post-operatively was associated with arthrofibrosis. Recently protocols have started restricting mobility for some surgical procedures which may place knees at risk for stiffness. It is critical to create a clinical reference tools to guide care based on recovery of knee ROM across time. We hypothesized that post-operatively knee extension ROM gains would plateau by 3 weeks and by 6 weeks for knee flexion. Secondarily, restricted knee motion post-operative will limit recovery of knee flexion for the first 6 weeks following surgery.
Participants: 185 patient charts that underwent ACLR between 2021-2023 at our institution were reviewed to produce 132 patients (77males, 55 females; age=25±11 years. Fourteen of these patients had various post-operative restrictions applied during the first two through six following ACLR for associated pathologies.

Methods

This retrospective case series extracted the following data: surgical procedure, date of surgery, date of physical therapy service, patient’s knee extension and knee flexion ROM for the first 16 weeks following surgery. At this facility, knee extension was measured passively with a negative value indicating hyperextension and knee flexion was measured actively assisted with patient using a strap around the ankle while in long sitting. All ACLR were included regardless of surgery being primary, secondary or having associated meniscal or ligamentous involvement. Data was analyzed using a linear mixed model for repeated measures with two factors, groups (restricted and non-restricted) by weeks for both flexion and extension separately, with significance set a p≤0.05.

Results

Knee extension revealed no significant group by week interaction (p=0.609) but significant main effects were found for weeks (p<0.001) and group (p=0.005). Bonferroni post-hoc analysis revealed significant improvement in extension from week 1 (0.3±4.5°) to week 2 (-1.8±3.0°) but no difference in extension after week 3 (-2.0±3.0°) regardless of group membership. The restricted group demonstrated 0.8±1.1° less knee extension over the non-restricted group regardless of the week (p=0.005). Knee flexion revealed significant interaction between group and weeks (p<0.001). Bonferroni post-hoc analysis demonstrated on average of 25 ± 29° deficit in the restricted patients regardless of the duration or amount of restriction imposed (p≤0.001).

Conclusion

Our hypotheses were supported as knee extension gains plateaued at 3 weeks and at 6 weeks for knee flexion. Any level of restriction imposed by the surgical procedure is associated with motion loss that is not recovered until nearly 2 months post-operatively. Clinicians should be concerned if patients are not nearing normal ranges of motion of extension (-3±3°) by 3 weeks and (138±8°) by 6 weeks post-operatively. Tracking weekly motion gains is an important objective indicator of recovery of function during the first 2 months following ACLR.