Patient-reported Outcomes and Muscle Strength after a Physiotherapy-led Exercise and Support Brace Intervention in Patients with Acute Injury of the Posterior Cruciate Ligament: A Two-year Follow-up Study

# Background While outcomes of posterior cruciate ligament (PCL) injuries treated surgically are well described, prospective studies reporting outcomes of exercise interventions are lacking. # Purpose The purpose of this study was to investigate changes in patient-reported outcomes of a physiotherapy-led exercise and support brace intervention in patients with acute injury of the PCL over a two-year follow-up period. Furthermore, this study sought to investigate changes in isometric knee muscle strength over an eight-month follow-up period, and finally to report conversion to surgical reconstruction over a two-year follow-up period. # Study design Case series study, prospective # Methods Fifty patients with an acute injury of the PCL were treated with a brace and a physiotherapy-led exercise intervention and followed prospectively. Changes in patient-reported outcomes were measured with the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) and the Knee injury and Osteoarthritis Outcome Score (KOOS) from baseline (diagnosis) to two-year follow-up. Furthermore, changes in isometric knee flexion and extension strength were measured with a static strength dynamometer from 16 weeks after diagnosis to one-year follow-up. Conversion to surgery was prospectively extracted from medical records. Mean changes were analyzed with a mixed effects model with time as a fixed factor. # Results The IKDC-SKF score improved 28 (95%CI 24-33) IKDC points from baseline to two-year follow-up. Isometric knee flexion strength of the injured knee increased 0.18 (95%CI 0.11-0.25) Nm/kg from 16 weeks after diagnosis to one-year follow-up, corresponding to an increase of 16%. In contrast, isometric knee extension strength of the injured knee did not change (0.12 (95%CI 0.00-0.24) Nm/kg, p=0.042). Over two years, seven patients converted to PCL surgical reconstruction. One and two-year follow-up were completed by 46 and 31 patients, respectively. # Conclusions The physiotherapy-led exercise and support brace intervention demonstrated clinically relevant improvements in patient-reported outcomes and knee flexion strength, and the risk of PCL surgical reconstruction was considered low within the first two years. # Level of evidence 3b ©The Author(s

Spectral Analysis of Instantaneous Power in Single-phase and Three-phase Systems with Use of p-q-r Theory

Instantaneous active power p, q-axis instantaneous reactive power qq, and r-axis instantaneous reactive power qr have been defined as linearly independent of each others in the time domain in three-phase four-wire systems with the use of p-q-r theory. This paper renames the instantaneous active/reactive powers as instantaneous real/imaginary powers to distinguish them from the traditional definition of active/reactive powers. The instantaneous real/imaginary powers are analyzed at various circuit conditions in single-phase and three-phase systems. The q-axis instantaneous imaginary power qq, is orthogonal to the other two instantaneous powers p and qr in the frequency domain. By analyzing the spectral distribution of the instantaneous powers p, qq, qr, this paper proposes unified definitions for some power quality factors which can evaluate and identify the various circuit conditions both for single-phase and three-phase systems.</p