A device for measuring knee joint movement

Abstract

This utility model relates to a knee joint motion measuring device. The device is installed at the knee joint and includes an upper connecting rod, a lower connecting rod, an angle encoder, a display unit, and a control box. The upper and lower connecting rods are connected, the angle encoder is installed at the connection point, and the control box is mounted on the upper connecting rod. The control box is communicatively connected to both the display unit and the angle encoder. This utility model collects the current angle change through the angle encoder, and the display unit processes the real-time data and visualizes the results, showing the current angle change trend. The angle measurement is accurate, and the results are displayed intuitively.

Description

Technical Field

[0001] This utility model relates to the field of knee joint angle measurement technology, and in particular to a measuring device for knee joint movement. Background Technology

[0002] Currently, while some progress has been made in technologies related to knee joint angular velocity or angular acceleration measurement, several significant limitations remain. In existing technologies, some accelerometer-based methods are widely used to detect gait information and indirectly calculate the knee joint's angular velocity through complex calculations, such as lower body posture recognition systems that use small accelerometers to measure joint motion angles. Inclinometers based on triaxial accelerometers utilize the output of a third accelerometer to solve for relevant angles, but their measurement accuracy cannot reach the arcsecond level due to factors such as accelerometer noise, model errors, angle calculation methods, ambient temperature, and magnetic field disturbances. Another approach uses triaxial geomagnetic decoupling and triaxial accelerometers. While this method can output roll / pitch attitude angles under ideal conditions without external acceleration interference, it is significantly affected by external acceleration in actual motion or vibration environments, resulting in significant errors in the output direction angle. Furthermore, accelerometers cannot accurately distinguish between gravitational acceleration and external force acceleration, leading to inaccurate data output during variable-speed motion. Some methods use gyroscopes to measure angles, but these typically suffer from cumulative integration errors and can only work relatively accurately within a short timescale. More importantly, these devices usually focus only on data acquisition and preliminary calculations, lacking the ability to perform in-depth processing and effective presentation of the acquired data. Users find it difficult to intuitively and clearly grasp the changing trends, characteristics, and underlying patterns of knee joint motion data.

[0003] Utility model patent CN111904426A discloses a method for measuring knee joint angles and its application, solving the problems of current knee joint angle measuring devices requiring multiple components, inconvenience in wearing, and inconvenience due to different leg lengths of people of different heights. It includes an angle measuring component comprising a fixed arm, one end of which is rotatably connected to a rotating arm, and the lower part of the rotating arm is rotatably connected to a footrest groove via a connecting plate. In use, this patent allows adjustment of the first and second movable plates according to the leg length of the person being measured, making the device suitable for people of different heights and convenient to wear. However, this patent suffers from inaccurate measurements and the inability to visualize the data.

[0004] Therefore, providing a measurement device that can measure accurately and visualize data is an urgent problem to be solved. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a device for measuring knee joint movement.

[0006] The objective of this utility model can be achieved through the following technical solutions:

[0007] According to one aspect of the present invention, a measuring device for knee joint movement is provided. The device is installed at the knee joint and includes an upper link, a lower link, an angle encoder, a display unit, and a control box. The upper link and the lower link are connected, the angle encoder is installed at the connection between the upper link and the lower link, and the control box is installed on the upper link. The control box is communicatively connected to the display unit and the angle encoder.

[0008] As a preferred technical solution, the device further includes a third screw, and the angle encoder is fixed to the upper connecting rod by the third screw.

[0009] As a preferred technical solution, the device further includes an intermediate shaft and a drive shaft. The intermediate shaft is mounted on the lower connecting rod, and the drive shaft is mounted on the intermediate shaft. The drive shaft is connected to the angle encoder.

[0010] As a preferred technical solution, the intermediate shaft, drive shaft and angle encoder are coaxial.

[0011] As a preferred technical solution, the angle encoder and the knee joint are coaxial.

[0012] As a preferred technical solution, the device further includes a retaining ring and a fourth screw. The intermediate shaft is connected and fixed to the upper connecting rod via the retaining ring, and the transmission shaft is connected and fixed to the angle encoder via the fourth screw.

[0013] As a preferred technical solution, the device further includes a hinge, the upper connecting rod includes a first upper connecting rod and a second upper connecting rod, the lower connecting rod includes a first lower connecting rod and a second lower connecting rod, the first upper connecting rod is connected to the second upper connecting rod via a hinge, the first lower connecting rod is connected to the second lower connecting rod via a hinge, and the second upper connecting rod is connected to the first lower connecting rod.

[0014] As a preferred technical solution, the device further includes a fixing unit, which is installed on the upper connecting rod and the lower connecting rod.

[0015] As a preferred technical solution, the fixing unit includes a fixing sleeve and a strap, the fixing sleeve is installed on the upper connecting rod and the lower connecting rod, and the strap is installed on the fixing sleeve.

[0016] As a preferred technical solution, the control box includes a control unit, a battery function board, and a Bluetooth unit. The battery function board is electrically connected to the control unit, the Bluetooth unit, and the angle encoder, respectively. The control unit is communicatively connected to the Bluetooth unit and the angle encoder, respectively. The Bluetooth unit is communicatively connected to the display unit.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This utility model collects the current angle change through an angle encoder, and the display unit processes the real-time data and visualizes the processing results to show the current angle change trend. The angle measurement is accurate and the result display is intuitive.

[0019] 2. The angle encoder of this utility model is installed at the knee joint, and the knee joint and the angle encoder are coaxial, ensuring that the rotation direction of the two is consistent, which can better detect angle changes.

[0020] 3. This utility model also incorporates a hinge, allowing both the upper and lower connecting rods to be finely adjusted according to different body shapes, enabling them to better fit the legs and improve measurement accuracy.

[0021] 4. This utility model uses a Bluetooth unit as a wireless communication module, which facilitates the transmission of real-time collected data to the display module for real-time display. Attached Figure Description

[0022] Figure 1 This is a front view of the present invention;

[0023] Figure 2 This is a side view of the present invention;

[0024] Figure 3 This is a top view of the present invention;

[0025] Figure 4 This is a schematic diagram of the installation of the angle encoder of this utility model;

[0026] Figure 5 This is an installation diagram of the present invention;

[0027] Figure 6 This is a schematic diagram of the measurement process of this utility model;

[0028] 1. Lower connecting rod; 2. Hinge; 3. Control box; 4. Upper connecting rod; 5. First screw; 6. Fixing block; 7. Strap; 8. Angle encoder; 9. Second screw; 10. Third screw; 11. Snap ring; 12. Fourth screw. Detailed Implementation

[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present utility model.

[0030] Example 1

[0031] like Figures 1-5 As shown, a knee joint motion measuring device is installed at the knee joint. The device includes an upper link 4, a lower link 1, an angle encoder 8, a display unit, and a control box 3. The upper link 4 and the lower link 1 are connected. The angle encoder 8 is installed at the connection between the upper link 4 and the lower link 1. The control box 3 is installed on the upper link 4 and is communicatively connected to the display unit and the angle encoder 8.

[0032] The device also includes a third screw 10, and the angle encoder 8 is fixed to the upper connecting rod 4 by the third screw 10.

[0033] The device also includes an intermediate shaft and a drive shaft. The intermediate shaft is mounted on the lower connecting rod 1, and the drive shaft is mounted on the intermediate shaft. The drive shaft is connected to the angle encoder 8.

[0034] The intermediate shaft, drive shaft, and angle encoder 8 are coaxial; the angle encoder 8 and knee joint are coaxial.

[0035] The device also includes a retaining ring 11 and a fourth screw 12. The intermediate shaft is connected and fixed to the upper connecting rod 4 via the retaining ring 11, and the transmission shaft is connected and fixed to the angle encoder 8 via the fourth screw 12.

[0036] The device further includes a hinge 2, the upper connecting rod 4 includes a first upper connecting rod and a second upper connecting rod, the lower connecting rod 1 includes a first lower connecting rod and a second lower connecting rod, the first upper connecting rod is connected to the second upper connecting rod via hinge 2, the first lower connecting rod is connected to the second lower connecting rod via hinge 2, and the second upper connecting rod is connected to the first lower connecting rod.

[0037] The device also includes a fixing unit, which is mounted on the upper connecting rod 4 and the lower connecting rod 1.

[0038] The fixing unit includes a fixing sleeve 6 and a strap 7. The fixing sleeve 6 is installed on the upper connecting rod 4 and the lower connecting rod 1, and the strap 7 is installed on the fixing sleeve 6.

[0039] The control box 3 includes a control unit, a battery function board, and a Bluetooth unit. The battery function board is electrically connected to the control unit, the Bluetooth unit, and the angle encoder 8. The control unit is communicatively connected to the Bluetooth unit and the angle encoder 8. The Bluetooth unit is communicatively connected to the display unit.

[0040] In this embodiment, the measuring device consists of an upper connecting rod 4, a lower connecting rod 1, a hinge 2, an angle encoder 8, a control box 3, a fixing block 6, and a strap 7. The lower connecting rod 1 is connected to the upper connecting rod 4 and the angle encoder 8 via an intermediate shaft and a transmission shaft, respectively.

[0041] Electronic components such as the battery power supply board, Bluetooth unit, and control unit are installed in the electrical control box 3, which is fixed to the upper connecting rod 4 by the first screw 5.

[0042] A hinge 2 is installed in the middle of both the upper link 4 and the lower link 1, dividing the upper link 4 and the lower link 1 into two parts. This allows the upper link 4 and the lower link 1 to rotate around the hinge 2 at a certain angle, resulting in a better fit when the device is worn on the human body.

[0043] Two sets of fixing units are installed on the upper connecting rod 4 and the lower connecting rod 1. Each set of fixing units includes a fixing sleeve 6 and a strap 7. The fixing sleeve 6 is fixedly connected to the upper connecting rod 4 and the lower connecting rod 1 respectively by the second screw 9.

[0044] The angle encoder 8 is fixed to the upper connecting rod 4 by the third screw 10. The lower connecting rod 1 is connected to the upper connecting rod 4 and axially fixed by the intermediate shaft and snap ring 11 on it. The rotating shaft on the lower connecting rod 1 is connected to the hole of the angle encoder 8, and the drive shaft is fixed to the angle encoder 8 by the screw 12, so that the drive shaft and the angle encoder 8 can rotate synchronously.

[0045] The measuring device is placed on the outside of the human leg. By adjusting the installation position, the rotation axis of the angle encoder is aligned with the human knee joint. The device is fixed to the human thigh and calf by four sets of fixing sleeves 6 and straps 7 installed on the upper connecting rod 4 and lower connecting rod 1. The hinges 2 installed on the upper connecting rod 4 and lower connecting rod 1 can rotate at a small angle, which can change the fit between the device and the curve of the human leg, thereby improving the comfort of the subject wearing the device and the accuracy of the measurement.

[0046] like Figure 6As shown, the workflow of this device for collecting, processing, and analyzing knee joint angle data is as follows: The test subject performs an action, interacting with the angle encoder 8. The angle encoder 8 transmits the collected angle data to the microcontroller (the control unit uses a microcontroller) within the control box 3. The display unit includes a display screen and a data processing terminal. After processing the angle data, the microcontroller wirelessly transmits the data to the data processing terminal via a Bluetooth unit also located within the control box 3. The data processing terminal simultaneously performs data analysis and image generation, and finally outputs the processing results to the display unit (specifically, a monitor) for presentation, thus fully realizing the entire process from knee joint angle data collection, transmission, processing to visualization. Alternatively, the data processing terminal can be omitted, as the control unit (microcontroller) processes the data and transmits it to the display unit for display.

[0047] Example 2

[0048] A measurement method for a measuring device used for knee joint movement, the measurement method comprising the following steps:

[0049] S1. Install the device correctly in place;

[0050] S2. Start the device and record the initial angle and initial time of the angle encoder 8;

[0051] S3. Obtain the angle change from the angle encoder 8 at preset time intervals to obtain a set of time and angle change;

[0052] S4. Based on the data in the set, fit an expression for the change of angle over time, draw a curve based on the expression, and display it through the display unit;

[0053] S5. Perform real-time differentiation on the expression to calculate the angular velocity and angular acceleration at the corresponding time.

[0054] In this embodiment, the measurement method includes two specific scenarios: swing measurement and walking measurement.

[0055] Swing measurement

[0056] This embodiment describes the use of a device for measuring changes in the angle of the human knee joint. The device consists of an angle encoder 8, an upper connecting rod 4, a lower connecting rod 1, a hinge 2, a fixing sleeve 6, and a control box 3. The angle sensor 8 is centrally located and cylindrical. The upper and lower connecting rods are connected to the angle encoder 8. The angle encoder used is model MK386C, with an accuracy of ±0.2°. The specific measurement process is as follows:

[0057] Place the subject in a quiet, undisturbed environment with sufficient space, and have them stand naturally with both knees straight. Securely fix the upper and lower connecting rods to the subject's thighs and calves respectively using the fixing sleeves, ensuring that the angle encoder is located directly in front of the knee joint and that the upper and lower hinges can rotate flexibly, ensuring that the device moves synchronously and stably with the knee joint during the measurement process.

[0058] Set the initial knee joint angle to 0°, start the measurement program in the control box, and record the starting time t0 = 0s. Instruct the subject to perform knee joint swinging movements at a moderate speed. The measuring device automatically starts timing, recording the knee joint angle A and the corresponding time t in real time at 0.1s intervals. The specific recorded data are shown in Tables 1 and 2.

[0059] Table 1

[0060]

[0061] Table 2

[0062] Time t(s) 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 Angle A° 34.1 32.5 29.6 25.5 20.6 14.5 9.4 5.3 2.2 0.6

[0063] While the measuring device records data, the wireless communication module in the control box synchronously transmits the real-time collected angle data A and the corresponding time data t to the paired terminal device. After receiving the data, the terminal device performs a fitting analysis, which can be done using polynomial fitting or other methods, to obtain the angle as a function of time:

[0064] A(t) = -0.34t 6 +2.85t 5 -9.32t 4 +14.43t 3 -8.08t 2 +2.46t

[0065] Calculate the derivative of this function:

[0066] (1) First derivative (angular velocity ω):

[0067] Taking the first derivative of A(t), we get:

[0068] ω(t)=A′(t)=-2.04t 5 +14.25t 4 -37.28t 3 +43.29t 2 -16.16t + 2.46

[0069] Substituting different time points into the angular velocity function:

[0070] When t = 0.5s, ω(0.5) = -2.04 × (0.5) 5 +14.25×(0.5) 4 -37.28×(0.5) 3 +43.29×(0.5) 2 -16.16 × 0.5 + 2.46 = 1.47° / s

[0071] When t = 1s, ω(1) = -2.04×15 + 14.25×14 - 37.28×13 + 43.29×12 - 16.16×1 + 2.46 = 4.52° / s (2) Second derivative (angular acceleration α):

[0072] Taking the second derivative of A′(t), we get:

[0073] α(t) = A″(t) = -10.2t 4 +57t 3 -111.84t 2 +86.58t-16.16

[0074] Substituting the angular acceleration function at different time points:

[0075] When t=0.5s, α(0.5)=-10.2×(0.5) 4 +57×(0.5) 3 -111.84×(0.5) 2 +86.58×0.5-16.16=5.65° / s 2

[0076] At t = 1s, α(1) = -10.2 × 14 + 57 × 13 - 111.84 × 12 + 86.58 × 1 - 16.16 = 5.38° / s 2

[0077] After the terminal device completes data processing, it visualizes the results, including curves showing the changes in angle, angular velocity, and angular acceleration over time. It also generates detailed data reports, recording the angle, angular velocity, and angular acceleration values ​​at each time point. In this knee joint motion measurement, the maximum angular velocity and maximum angular acceleration can be further derived by comparing all calculated data.

[0078] In the measurement method of this utility model, multiple sets of data are collected and fitted into corresponding equations. The first and second derivatives of the equations are then performed to calculate the corresponding angular velocity and angular acceleration. An appropriate step size can be selected according to the accuracy requirements.

[0079] Example 3

[0080] Walking measurement

[0081] This embodiment describes the use of a device for measuring changes in the angle of the human knee joint. The device consists of an angle encoder, an upper connecting rod, a lower connecting rod, a hinge, a fixing sleeve, and a control box. The angle sensor is centrally located and cylindrical. The upper and lower connecting rods are connected to the angle encoder. The angle encoder used is model MK386C, with an accuracy of ±0.2°. The specific measurement process is as follows:

[0082] Choose a quiet, spacious, and level area for the subject, allowing them to stand in a natural and comfortable posture with their knees naturally straight. Securely fasten the upper and lower connecting rods to the subject's thighs and calves using the fixing sleeves, ensuring the angle encoder is accurately positioned to the side of the knee joint. Simultaneously, adjust the upper and lower hinges to allow for flexible rotation, ensuring the device remains synchronized and stable with the knee joint's movement throughout the measurement process.

[0083] Set the initial knee joint angle to 0°. Activate the measurement function in the control box and accurately record the starting time t0 = 0s. Instruct the subject to begin walking at a normal walking speed and rhythm. The measuring device automatically activates its timing function, recording the knee joint angle A and the corresponding time t in real time at 0.1s intervals. Specific recorded data are shown in Tables 3 and 4.

[0084] Table 3 Table 4

[0085]

[0086]

[0087] While the measuring device records data, the wireless communication module in the control box synchronously transmits the real-time collected angle data A and the corresponding time data t to the paired terminal device. After receiving the data, the terminal device performs fitting analysis to obtain the angle as a function of time:

[0088] A(t) = -0.35t 5 +2.24t 4 -4.69t 3 +3.83t 2 +3.05t.

[0089] Derivative calculation:

[0090] (1) First derivative (angular velocity ω):

[0091] Taking the first derivative of A(t), we get:

[0092] ω(t)=A′(t)=-1.75t 4 +8.96t 3 -14.07t 2 +7.66t +3.05

[0093] Substituting different time points into the angular velocity function:

[0094] When t = 0.5s, ω(0.5) = -1.75 × (0.5) 4 +8.96×(0.5) 3 -14.07×(0.5) 2 +7.66×0.5+3.05

[0095] =4.37° / s

[0096] When t = 1s, ω(1) = -1.75×14 + 8.96×13 - 14.07×12 + 7.66×1 + 3.05 = 3.85° / s

[0097] (2) Second derivative (angular acceleration α):

[0098] Taking the second derivative of A′(t), we get:

[0099] α(t)=A″(t)=-7t 3 +26.88t 2 -28.14t +7.66

[0100] Substituting the angular acceleration function at different time points:

[0101] When t = 0.5s, α(0.5) = -7 × (0.5) 3 +26.88×(0.5) 2 -28.14 × 0.5 + 7.66 = -0.56° / s 2

[0102] When t = 1 s, α(1) = -7 × 13 + 26.88 × 12 - 28.14 × 1 + 7.66 = -0.6° / s 2

[0103] After the terminal device completes data processing, it visualizes the results, including curves showing the changes in angle, angular velocity, and angular acceleration over time. It also generates detailed data reports, recording the angle, angular velocity, and angular acceleration values ​​at each time point. In this knee joint motion measurement, the maximum angular velocity and maximum angular acceleration can be obtained by comparing all calculated data.

[0104] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A device for measuring knee joint movement, the device being installed at the knee joint, characterized in that, The device includes an upper connecting rod (4), a lower connecting rod (1), an angle encoder (8), a display unit, and a control box (3). The upper connecting rod (4) and the lower connecting rod (1) are connected. The angle encoder (8) is installed at the connection between the upper connecting rod (4) and the lower connecting rod (1). The control box (3) is installed on the upper connecting rod (4). The control box (3) is communicatively connected to the display unit and the angle encoder (8).

2. The knee joint motion measuring device according to claim 1, characterized in that, The device also includes a third screw (10), and the angle encoder (8) is fixed by the third screw (10) and the upper connecting rod (4).

3. The knee joint motion measuring device according to claim 2, characterized in that, The device also includes an intermediate shaft and a drive shaft. The intermediate shaft is mounted on the lower connecting rod (1), and the drive shaft is mounted on the intermediate shaft. The drive shaft is connected to the angle encoder (8).

4. The knee joint motion measuring device according to claim 3, characterized in that, The intermediate shaft, drive shaft and angle encoder (8) are coaxial.

5. The knee joint motion measuring device according to claim 3, characterized in that, The angle encoder (8) is coaxial with the knee joint.

6. The knee joint motion measuring device according to claim 3, characterized in that, The device also includes a snap ring (11) and a fourth screw (12). The intermediate shaft is connected and fixed to the upper connecting rod (4) via the snap ring (11), and the transmission shaft is connected and fixed to the angle encoder (8) via the fourth screw (12).

7. The knee joint motion measuring device according to claim 1, characterized in that, The device further includes a hinge (2), the upper link (4) includes a first upper link and a second upper link, the lower link (1) includes a first lower link and a second lower link, the first upper link is connected to the second upper link via the hinge (2), the first lower link is connected to the second lower link via the hinge (2), and the second upper link is connected to the first lower link.

8. The knee joint motion measuring device according to claim 1, characterized in that, The device also includes a fixing unit, which is mounted on the upper connecting rod (4) and the lower connecting rod (1).

9. The knee joint motion measuring device according to claim 8, characterized in that, The fixing unit includes a fixing sleeve (6) and a strap (7). The fixing sleeve (6) is installed on the upper connecting rod (4) and the lower connecting rod (1), and the strap (7) is installed on the fixing sleeve (6).

10. A knee joint motion measuring device according to claim 1, characterized in that, The control box (3) includes a control unit, a battery function board and a Bluetooth unit. The battery function board is electrically connected to the control unit, the Bluetooth unit and the angle encoder (8) respectively. The control unit is communicatively connected to the Bluetooth unit and the angle encoder (8) respectively. The Bluetooth unit is communicatively connected to the display unit.

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