# Developmental Screening System for Patient Vibration Signals with Knee Disorder
## 1 Introduction  
The knee joint, the most complex joint in the human body, includes the anterior cruciate ligament (ACL), lateral collateral ligament (LCL), medial collateral ligament (MCL), and posterior cruciate ligament (PCL) for stabilization during movement. Movement is promoted by nerve signals to the skeletal leg muscles that are transferred via tendons attached to the knee. The knee joint is exposed to a reaction force when the lower limbs perform floor exercises. Momentarily exposing the knee joint to excessive or uneven reaction forces that cannot be absorbed by the musculoskeletal system may make the knee joint unstable, thus worsening any ligament or tendon injury [1; 2]. A knee joint injury limits movement and physical activity. Swelling and pain with an acute knee injury can be alleviated by ice-pack application and/or anti-inflammatory drugs. Walking with a crutchmay also reduce the load on the knee joint. After these acute symptoms pass, some patients mistakenly think that the injured knee-joint has recuperated, while in fact the knee joint is still damaged. Further use of the knee without a full recovery can lead to degenerative arthritis over time. To resolve knee joint instability, the human body attempts to adapt itself to the situation. This further weakens the knee joint, resulting in progressive wear and tear, and eventually, the onset of osteoarthritis (OA). Although medications can be used to control inflammation and acute pain symptoms, more serious knee ligament injuries may require ligament reconstruction surgery to treat lower extremity discomfort or improve biomechanical performance to restore knee joint stability and exercise ability [3]. Knee joint ligament injuries occur often in sports, traffic accidents, and with serious falls. Sixty percent of knee joint injuries involve the ACL [4]. The Lachman test is used for clinical investigation of the ACL [5], with a predictive value approaching 91.7% for tears or partial tears; however, the average correct diagnostic rate using the Anterior Drawer test is only 66.8%. Hence, the Lachman test is often the preferred diagnostic approach. The average predictive accuracy for clinical investigation of MCL rupture through abduction and valgus stress tests is 76.5%. Fewer patients present with LCL damage compared with ACL cases. Thus, the rate of LCL injuries is lowest among the four types; the average predictive accuracy is 25% for LCL rupture, with adductor stress testing and gorystyposis assessment. Hence, other clinical approaches to diagnose MCL and LCL ruptures are required to improve the diagnostic accuracy of an ACL injury. Ligament damage affects the daily lives of those afflicted. The necessity of ligament reconstruction surgery depends on the patient's age, working environment, activity interests, habits, and the ability to navigate the short-term postoperative loss of movement during recovery [6]. If the patient refuses to undergo surgery or a muscle rehabilitation program and is unwilling to wear kneepads or alter body movements, other conservative treatment methods can be used; however, only 9% of motor function is recovered [7]. In orthopedic clinics, the need for ligament reconstruction surgery is determined by the recovery of the injured tibia, the amount of displacement of the femur, and joint function; in addition, a physical examination is used to assess the overall health of the patient [8]. In [9; 10], the results showed that ACL reconstruction surgery cannot fully restore the dynamic function of the knee joint and may actually increase the likelihood of degenerative joint disease. A study involving 45 patients with healthy ACLs and 45 patients who had undergone ACL reconstruction surgery was conducted to confirm the effects of early OA with lower extremity biomechanical changes following ACL reconstruction surgery [11]; the results showed that in patients with lower limb injury, the body's natural compensatory mechanism is activated, resulting in an increased load on the other, undamaged knee.