# Developmental Screening System for Patient Vibration Signals with Knee Disorder
## 1 Introduction
However, the results could not prove that the increased load causes OA after surgery, as torque changes can also lead to OA. In [12; 13; 14], differences between the injured leg and the healthy leg under preoperative and postoperative surgical examinations were evaluated in terms of the constant velocity attained with ACL reconstruction. The efficiency of ACL reconstruction with postoperative surgery was investigated in [15]; the experimental results showed that time-frequency analysis of various knee joint features can be used to evaluate the status of the knee joint and rehabilitation progression. In [16], researchers evaluated the applicability and efficiency of ACL reconstruction rehabilitation using a special whole-body vibration muscle exercise; rehabilitation was evaluated and given a Lysholm score at weeks 2, 5, 8, and 11, with respect to the original ACL length and velocity. In [17; 18; 19; 20; 21], the rehabilitation efficiency of ACL reconstruction was evaluated based on a visual analogue scale, Lysholm score, and a numerical rating of the applicability and pain of the knee joint; the results indicated that the inclusion of stability indicators in the recovery diagnostic tool provides an accurate representation of the reconstruction process. Many studies e.g., [22; 23; 24] have proven the feasibility of using noninvasive sound detection methods for identifying knee joint disorders. In [25], the knee pathology was identified and diagnosed based on a noninvasive approach using sound signals in 6 patients with non-normal known knee pathologies and in 11 patients with suspected knee injury; the patients were ultimately divided into two groups consisting of (1) those with a damaged meniscus or ACL tear that required a clinical diagnosis by a physician and surgical treatment and (2) those with degenerative arthritis. [PERSON]'s research group at the University of Calgary [26] extracted a fractal scaling index and average sound amplitude by analyzing the joint vibration data of 75 participants with knee joint injuries; they identified degenerative arthritis using vibroarthrographic signal data and Kolmogorov-Smirnov analysis results. Currently, magnetic resonance imaging (MRI), X-ray imaging, and computed tomography are used to examine internal joints in a non-invasive procedure. The gold standard method for determining the extent of damage to the knee joint is arthroscopic examination. However, arthroscopy cannot be used for early detection or postoperative analysis of rehabilitation progression. Moreover, the arthroscopic exam is an invasive procedure conducted under general anesthesia with associated surgical risks. Sound is produced in the soft tissue of normal, uninjured knees due to air pressure variations that occur when the knee joint is rubbed or squeezed during buckling or straightening. In the presence of an existing injury, the lower limb produces abnormal sounds during cyclic bending action [27; 28]. Abnormal murmurs in the joints on clinical examination may indicate joint disorders. The purpose of this study was to provide scientific data to help physicians assess the rehabilitation progression following knee ligament reconstruction surgery. Based on the vibration and sound generated with bending and swinging of the injured knee joint, the recorded sound signals from audio sensing and inertial sensing modules, respectively, were used to assess the rehabilitation progression of the knee joint. Three testing sites around the knee joint corresponding to the ACL, MCL, and LCL were monitored. The sound signals were transformed into discrete wavelets, from which characteristic parameters were extracted for data analysis. Statistical analysis of the data was used to determine the extent of the joint injury. By tracking the status of patients before and after surgery, the patient's own sound signals can be used to evaluate the rehabilitation status of the joint.