## 1 Introduction  
Osteoarthritis (OA) is a common condition reported in females more frequently than in males [1]. It typically affects joints in hands, feet, spine, knees, and hips [2]. Primary symptoms reported by patients suffering from osteoarthritis of the knee (OAK) include pain, stiffness, decreased mobility, and muscle weakness [1, 3]. [PERSON] et al. [4] have proven that radiologically confirmed OAK is associated with problems with walking, self-care, and activities of daily living (ADLs). It has been shown by researchers that ADLs are affected not only by the pain reported but also by the range of motion [5]. The range of motion (ROM) may decrease due to pain, loss of elasticity in connective tissue structures, or bone abnormalities [6].  
Most authors suggest that the range of 100-110 degrees in the knee is necessary for activities of daily living [7, 8]. It has been noted, however, that a number of available studies evaluated functions, such as gait, climbing and descending stairs, i.e., activities that typically cannot be avoided or replaced [7, 8].  
However, there are a number of other activities that require a larger range of knee motion, such as getting into a bathtub, gardening, DIY, or changing socks. Some of these activities are commonly performed while squatting when the knee flexion range significantly exceeds 110 degrees. This was noted by [PERSON] et al. who assessed hip, knee, and ankle angles required for various activities of daily living, such as dressing, using the toilet, bathing, picking up objects, and crouching [5]. It has been found that the knee flexion angle when getting into a standard bathtub was approximately 125 degrees, while trunk rotation during crouching required as much as 149 degrees [5]. Those who cannot achieve the required range of motion, no longer perform the activity or establish their own movement patterns, and this may cause other structures to be overloaded [9].  
[PERSON] [10] suggests that activities of daily living more commonly involve closed kinematic chains or mixed sequences in which open and closed kinematic chains movements are alternately performed during different phases of an activity. More and more rehabilitation protocols include closed kinematic chain exercises; however, it is interesting to note that therapeutic efficacy is rarely evaluated based on closed kinematic chain tests only.  
Treatment aiming to improve the range of motion in a joint depends on the cause of impairment. Major structural abnormalities in the joint frequently require surgical intervention [11]. Conservative treatment achieves satisfactory effects when impairment is due to other causes. The conservative treatment strategies to improve the range of motion include stretching exercises, passive exercises, active assisted exercises, manual therapy, and any physical procedures and exercises to alleviate pain and improve neuromuscular coordination which also improve the range of motion.  
When reviewing the available study results, we have found that no research has been performed to determine the effect of specific therapeutic procedures on the range of motion and how they affect ADLs.  
Therefore, this study aimed to answer the following questions:  
1. Can we influence the range of movement within ten days of rehabilitation through manual therapy or synergistic movement lower limb exercises in the closed kinematic chain?  
2. Which of the proposed physiotherapeutic methods better affects the range of movement?  
3. Is testing in different biomechanical conditions useful for assessing the range of motion?  
4. What are the further guidelines for a long-term physiotherapeutic protocol to improve OAK patients' range of movement?  
Our study evaluated the short-term effect after 10 days of daily therapy, which was sufficient to evaluate certain tendencies and design further stages of rehabilitation showing greater effectiveness.