FR2590151A1 - Electronic ambulatory apparatus for locomotary recording and/or reeduction - Google Patents

Abstract

The subject of the invention is portable electronic apparatuses for locomotory recording and/or reeducation. An apparatus according to the invention includes a goniometer which is composed of two arms 3a, 3b fixed on the external side of the thigh and the leg and a potentiometer 5 which is placed at the knee joint and which delivers an analog signal proportional to the angle of bending of the leg. It furthermore includes a central processing unit which is placed in a back pack 1 and which is associated with a cassette drive 8 and a keyboard 7, which allows programs recorded on the cassettes or numerical data, in particular knee extension threshold values to be loaded into the RAM of the central processing unit. It may furthermore include an ambulatory stimulator 11 which is connected to transcutaneous electrodes 12a, 12b acting on the muscles which lift the foot. One application is the reeducation of hemiplegics.

Description

 The subject of the present invention is an ambulatory electronic device for recording the essential parameters of walking and for making it possible to rehabilitate patients suffering from impairments.

 The technical sector of the invention is that of the construction of electronic measuring devices and locomotor rehabilitation devices.

 The sick and disabled, such as hemiplegics, for example, have locomotor abnormalities, including the extension or even hyperextension of the supporting leg, which is called the knee recurvatum. This is a deficiency which has several drawbacks both for the walk itself which loses its effectiveness and which is unsightly, as for the mechanics of the knee because it leads to a progressive deterioration of the joint.

 The knee recurvatum is difficult to correct with traditional rehabilitation methods.

 Other locomotor abnormalities are the tendency not to lift the foot and not flex the leg enough when walking.

 We know different ways to study the kinematics of locomotion.

 One of these known means consists in recording video or cinematographic images of the movement or in decomposing the movements by means of photographs taken at high speed at successive moments very close together. These means make it possible to obtain mobile or fixed images which can be observed.

Another known means is described in an article entitled
Walking telemetry by JJ RAINAUT and J. LOTTEAU which was published in the Journal of Orthopedic Surgery No. 2 in March 1974.

 This article describes a portable device comprising a potentiometric goniometer fixed to the leg of a subject and a frequency modulation transmitter which analogically converts the signal delivered by the potentiometer into a variable frequency. The portable device is associated with a fixed receiver provided with a decoder which transforms the variations of frequency into variations of direct voltage which are recorded by a needle on a sheet of paper.

 This prior device makes it possible to obtain curves representing the angle of flexion of a leg around the knee and to establish correlations between the muscular activities, which can also be recorded and the movements of the leg.

 However, it is a complex device which requires the use of a portable radio transmitter associated with a fixed radio receiver. In addition, graphic recordings do not allow precise and adjustable digital thresholds to be set. The device described in this previous document cannot be used as a portable rehabilitation device.

An article published in Arch. Phys. Med. Rehabil - volume 84 - August 1983, entitled "'Genu Recurvatum: Auditory Biofeedback treatment for adult patients with stroke or head injuries" by Raymond
E. Hogue and Sylvia Mc Candless describes a rehabilitation device constituted by an electro-goniometer which is fixed on the leg of a subject and which comprises a channel in the form of a slide carrying a microswitch which is actuated by a plastic bar which moves in said channel when the leg is extended beyond a threshold. The microswitch activates an audible alarm. This known device does not make it possible to obtain records and it does not allow the value of the recurvatum threshold to be easily modified.

 An object of the present invention is to provide an electronic device for recording and / or for re-educating locomotion, in particular the movements of flexion of the leg around the knee, which can be easily transported by a subject, without any discomfort, so that the movements of walking are not modified by the use of this device and that it can be easily used for rehabilitation sessions.

 Another objective of the present invention is to provide an electronic device which makes it possible to quantify certain essential parameters of the movements of locomotion, in particular the movements of flexion of the leg around the knee in the sagittal plane and to compare the numerical values with thresholds, in particular to a knee extension threshold, which can be easily introduced into the device and modified by a rehabilitator.

 Another object of the invention is to provide an electronic device which can be associated with a graphic printer which traces the curves for recording the angle of flexion of the leg, which curves make it possible to keep track of the results achieved and of '' make comparisons of several successive recordings in order to assess the development over time and the effectiveness of rehabilitation.

 Another object of the invention is to provide an electronic device which emits an audible signal to warn the patient each time he reaches a threshold, for example a knee extension threshold, which can be modified by the rehabilitator during successive rehabilitation sessions to increase the effectiveness of rehabilitation.

 Another objective of the invention is to provide a rehabilitation device which calculates and records the number of exceedances of a threshold, for example the extension threshold during each rehabilitation session and which emits at the end of each session. an audible signal indicating the number of exceedances of said threshold.

 Another object of the invention is to provide a portable electronic device which can be combined with a portable electric stimulator to control the emission of stimulation signals from nerves or muscles, in particular of the levator muscles, at determined times of each step and for a fixed duration and which allows to easily modify the moment of the beginning of each stimulation and the duration of this one.

The objectives of the invention are achieved by means of an electronic device for recording and / or rehabilitating locomotion which comprises:
- an angular sensor placed at the knee of a patient, which delivers an analog electrical signal representing the angle of flexion of the leg;
- an electronic calculation unit carried by the patient, which comprises an interface circuit which receives the analog signals and which comprises an analog to digital converter which samples the analog signals and converts them into digital values; a microprocessor and a random access memory which stores said digital values;
- a magnetic cassette recorder-player;
- And a keyboard which makes it possible to introduce into said random access memory a program recorded on cassette and / or digital data.

 Advantageously, an apparatus according to the invention further comprises a loudspeaker which emits an audible signal when the knee extension angle exceeds a threshold, the value of which can be modified by means of said keyboard.

 Advantageously, an apparatus according to the invention further comprises a microswitch which is placed in the shoe and which is connected to the analog to digital converter of said interface circuit.

According to a preferred embodiment, an apparatus according to the invention comprises one or more portable functional electrical stimulation apparatuses which are connected to transcutaneous electrodes placed on a nerve or on a muscle and relays which are controlled by said microprocessor when certain thresholds are exceeded and who control said stimulation devices
Advantageously, a device according to the invention is associated with a graphic printer to which it is connected after a rehabilitation session and it includes a program which controls the printing by the printer of a curve representing the variations in the angle of knee flexion. j
The invention results in a new portable electronic device intended to quantify and record the movements of the leg, in particular the angular movements in the sagittal plane around the knee joint and which can be used to rehabilitate patients suffering from locomotor deficiencies, especially hemiplegics.

 An advantage of the devices according to the invention lies in the fact that they make it possible to fix thresholds with very high precision, in particular a knee extension threshold with a precision of 10, to detect the exceedances of said threshold, to transmit an audible signal which warns the patient in real time of this overshoot, of calculating at the end of a session the number of overshoots of said threshold and of informing the patient by sound of this number of overshoots, which has the effect of improve the effectiveness of rehabilitation sessions.

 Another advantage of the apparatuses according to the invention resides in the fact that they make it possible to electrically stimulate certain muscles, in particular the lifting muscles of the foot at well-defined instants within each step and for a well-defined duration. , which instant and duration are fixed simply by means of an alpha-numeric keyboard and can be modified very easily.

 Another advantage of an apparatus according to the invention lies in the fact that it makes it possible to trace by means of a graphic printer the flexion curves of the leg around the knee and to transfer the positions and the durations on the same graph. of support on the ground of the foot and the electrical stimulations of a muscle. The graphical recordings of the angle of flexion in correlation with the writing on the same graph of the contacts of the foot with the ground make it possible to obtain a precise quantification of the locomotor deficiencies and an appreciation of defects which are not perceived during a visual examination. They allow to follow the evolution of the recovery of movements during successive rehabilitation sessions. The knee extension thresholds which are fixed by means of the keyboard can be modified at the beginning of each rehabilitation session as and when progress made.

 Graphic recordings are very important for the rehabilitator because they allow him to objectively assess the precise effects of the rehabilitation treatments obtained by the subject's reactions to the sound signals of exceeding the threshold of extension and by the muscular stimulations which have an effect. rehabilitative. The graphic recordings also allow the rehabilitation worker to appreciate the effects of the instructions given to the patient. Finally, graphic recordings make it possible to keep a written record of a patient's progress which can be consulted at any time to establish comparisons over time.

 The known systems for studying movements of locomotion do not allow the same sum of results to be obtained by means of a single portable device.

 Telemetry recordings are much more expensive and they are subject to many constraints: limited distance, interference, etc.

 Recordings of mobile video or cinematographic images are much less precise and more difficult to consult. They do not allow for rehabilitation with thresholds and sound feedback. The same is true of recordings of photographs breaking down a movement. There are also records of movements of locomotion using very sophisticated optical devices, difficult to implement and of a very high unit price and these optical devices do not make it possible to obtain a precise quantification of the movement, with means as simple and easy to implement as the devices according to the invention.

 The results obtained with a device according to the invention in the rehabilitation of the knee recurvatum are very positive.

 The number of exceedances of the limit value, counted by the computer, generally falls from several tens per minute at the start of rehabilitation to a few units per session after a few weeks of rehabilitation and this improvement continues after the cessation of rehabilitation. . These results are obtained even with patients with hemiplegia of more than a year, while the spontaneous evolution of the locomotor restoration is practically finished.

 An apparatus according to the invention which calculates and indicates the number of breaches of the threshold per rehabilitation session or the number reduced to the unit of time makes it possible to objectively assess the results obtained.

 A device according to the invention can be used to correct defects in locomotion other than the knee recurvatum. It can be used for example to correct any defect resulting in abnormal values of the knee flexion angle. This is particularly the case for patients with insufficient knee flexion or, on the contrary, those who walk in flexion, that is to say with insufficient extension of the leg. It suffices to choose other angular threshold values and possibly to change the setpoint given to the subject by asking him for example to obtain an audible signal instead of avoiding it.

 The following description refers to the accompanying drawings which show, without any limitation being, an embodiment of an apparatus according to the invention.

 Figure 1 is an overview of a device worn by a patient.

 FIG. 2 is a diagram representing the essential electronic components as well as the sensors and stimulators of a device according to the invention.

 Figures 3 to 5 are diagrams of the bending movements of the leg.

 FIG. 1 represents a portable electronic device which comprises a bag 1 which is hung on the back of a patient while the patient is walking and a sensor 2 of angular displacement which is fixed on the side of a leg at the level knee. The patient suffers from neurological deficiencies which lead to locomotion abnormalities. For example, this is a hemiplegic who starts walking again and whose deficient leg needs to be rehabilitated.

 Most often for such a patient, during the mark, the defective knee joint comes into abutment, during the extension of the leg and in this position, the angle of flexion which is the angle formed by the extension of the thigh with the lower leg, reaches and even exceeds the zero value corresponding to the alignment. This abnormality is known as a knee recurvatum.

The sensor 2 is a goniometer which makes it possible to measure the angle of flexion of the leg. The sensor 2 comprises two arms 3a, 3b which are hinged together to form a compass One of the arms
j 3a is fixed on the external side of the deficient thigh while the other arm 3b is fixed on the external side of the calf, so that the axis of articulation is aligned with the axis of articulation of the movement of the knee in the sagittal plane.

 The arms 3a, 3b are fixed by means of straps 4 which are provided for example with a quick fastening system with loops and hooks or any other equivalent fastening system.

 In order to avoid the sliding of the arms 3a, 3b, the internal faces of the latter are advantageously provided with an anti-slip adhesive.

 The two arms 3a and 3b are connected one to the fixed housing and the other to the movable contact of a precision potentiometer 5 which is supplied with a direct voltage, for example a voltage of 5 volts and which emits a voltage proportional to the angular displacement, which tension emitted constitutes an analog signal of the angle of bending.

 Advantageously, the potentiometer is associated with a protractor 6 which is fixed in such a way that the center of the protractor coincides with the axis of the potentiometer. The protractor 6 allows an operator to visually take measurements of the bending angle and to check the correct positioning of the goniometer.

 The bag 1 contains an electronic calculation unit and peripheral units thereof. It contains in particular an alpha-numeric keyboard 7 which is easily accessible from the rear.

 It also contains a magnetic cassette recorder and reader 8 which has a full remote control by relay of all its functions: recording, playback, fast forward, fast backward, pause, stop.

 This remote control makes it possible to automatically control the operation of the recorder from the central computing unit for example to automatically transfer to a cassette the data recorded in your RAM memory of the central unit when this memory is full. The recorder 8 makes it possible to introduce into the random access memory of the central unit recorded programs. It also makes it possible to record on a cassette, at the end of a reeducation session, the digital data recorded in the random access memory then to transport the cassette on a cassette player associated with another microcomputer to transfer to j last digital data.

 The second microcomputer is associated with a graphic printer and is programmed to trace, by said printer, on a sheet of paper, the flexion curves of the leg during part of a rehabilitation session and to calculate the number exceeding the extension threshold during a rehabilitation session and / or per time unit.

 The bag 1 still contains a small rechargeable accumulator battery which supplies the electronic circuits.

 FIG. 1 represents an example of preferential use in which the shoe of the patient's sick leg preferably comprises, in the heel, a sensor 9 of time of contact with the ground which is a switch which closes when the pressure d support is sufficient. The sensor 9 is connected by a conductor 10 to a two-phase input of the interface circuit of the electronic computing unit. When switch 9 is closed, this input is grounded.

 Alternatively, other sensors can be used. For example, one can have strain gauges under the sole to measure the ground pressure of one leg or both legs.

 These gauges are also connected by conductors to the interface circuit of the central processing unit and the analog signals are converted by sampling into digital values which are recorded and which can be compared with thresholds.

 This measure also rehabilitates hemiplegics who tend not to lean enough on the ground.

 The electromyographic activity of certain muscles can also be recorded by means of transcutaneous electrodes. In this case, the signal delivered must be amplified, rectified and integrated to obtain an analog signal which is the envelope of the electromyographic signal which is a signal oscillating at high frequency.

 FIG. 1 represents an example of use on a hemiplegic patient whose foot tends to remain inclined downward during the flexion of the leg because the lifting muscles of the foot escape the control of the patient. In this case, the patient carries an ambulatory electrical stimulation device 11 which can be placed in the bag 1 or hung on the dye and which comprises two transcutaneous electrodes 12a, 12b of different polarity, which are applied either to the lifting muscles of the foot , or on the path of the nerve that controls them, that is to say the sciatic nerve external popliteal.

 The electrical stimulation device 11 is a known device which is used in functional rehabilitation centers and, in this case, the control of the stimulations is generally carried out by a rehabilitator who permanently attends a rehabilitation session and which manually triggers the stimulation. at the time of each cycle which seems to him the most appropriate, this method being very restrictive and imprecise. As a variant, the stimulations are triggered automatically by a switch placed under the sole when the foot leaves the ground and are stopped at the moment of support, which does not always coincide with the most appropriate moment and duration.

 The ambulatory stimulation device 11 sends on the electrodes a train of electric waves which automatically stimulate the lifting muscles of the foot and cause their involuntary contraction and lifting of the foot. The device 11 is for example a device sold under the brand "Stipel" by La Société dit: Electronique 2000. The association of an ambulatory stimulator 11 and an apparatus according to the invention makes it possible to control the stimulator by relays which are themselves controlled by the unit of central calculation and thus to set with great precision the start of each stimulation at a well-determined instant of each step, to also set the duration of each stimulation and to be able to modify these numerical values at will.

 An apparatus according to the invention may include other electrical stimulators acting on other muscles, for example on the muscles which control the flexion of a leg in the case of a patient who tends not to flex it sufficiently.

 An apparatus according to the invention also includes a built-in speaker 13 which emits an audible signal each time a threshold is exceeded1 for example each time the extension threshold set at the start of a rehabilitation session is exceeded.

 FIG. 2 schematically represents the essential electronic components of an apparatus according to the invention.

 The reference 14 represents a central unit which is an integrated circuit microprocessor. The reference 15 represents a random access memory (RAM) in integrated circuits. The reference 16 represents a read only memory (ROM or PROM) in which the program of operations to be carried out by the microprocessor is recorded. The reference 17 represents the bus lines of the central unit. The reference 18a represents an interface unit. We find on the left of the figure the potentiometer 5 and the microswitch 9 which are connected on the interface unit 18a. Also shown on the left of the figure is an electrode 19 which is, for example, a myographic electrode making it possible to record the activity of a muscle. The keyboard 7 is found on the left of the figure. The reference 18b represents an interface unit between the central unit and various output peripherals.

 We find on the right of the figure the speaker 13 as well as an ambulatory stimulator 11 which is connected to two transcutaneous electrodes 12a, 12b intended to stimulate the lifting muscles of the foot.

 There is also the cassette micro-recorder 8.

There is also shown a graphic printer 20 which can be connected to the output interface 18b at the end of a session to establish graphics representing the flexion movements of the leg carrying the potentiometer 5. In this case, the microprocessor 14 is programmed to provide the printer, in deferred time, with the data necessary for establishing the graphics.

 As a variant, the data recorded during a rehabilitation session can be transferred at the end of the session, to a cassette thanks to the micro-recorder 8 associated with the device, then the recorded cassette can be transferred to the memory of a microphone. -computer which is associated with a graphic printer and which is programmed to process the recorded data and to establish the corresponding graphics.

 An apparatus according to the invention can be used to study the progress of a patient or to re-educate him and he has for this purpose several software which can be introduced separately or simultaneously into the RAM 15 by means of recorded cassettes read by reader 8.

 The keyboard 7 makes it possible to send the software loading orders to the central unit.

 An apparatus according to the invention advantageously comprises a voice synthesizer and it is programmed to emit a vocal sound signal, for example the word "ready" when a software has been recorded and the apparatus is ready to operate.

 Advantageously, three software programs are used: a first data recording software; a second software for setting and detecting a threshold, for example a threshold for extending and emitting an audible signal each time the threshold is exceeded; third muscle stimulation software, for example stimulation of the lifting muscles of the foot.

 During a data recording or rehabilitation session, the operator begins by attaching the goniometer 5 to the external side of a patient's deficient leg, aligning the axis of the potentiometer as closely as possible with the axis of articulation of the sagittal movement of the knee.

 A calibration of the reference signal taken as the zero value of the bending is then carried out. The patient is asked to bring his leg into the maximum extension position in which the joint is in abutment and a key on the keyboard is pressed to instruct the computer to record the value of the signal delivered by the patient. potentiometer in this position. This value is taken subsequently as zero reference value, corresponding to a zero bending angle. The measurement of the real bending angle in the maximum extension position can be noted at the same time on the protractor 6, which then makes it possible to correct the curves drawn by the printer to bring these curves back to a geometric zero value, that is, the value in which the thigh and your leg would be in alignment.

 At the start of a knee recurvatum reeducation session, a limiting angle of extension is introduced using the keyboard, which can be changed during successive sessions to take account of the progress made by the patient.

 The duration of the session is also introduced at the start of a session, which can be adapted to each patient and which can be varied for the same patient during successive sessions.

During a recurvatum rehabilitation session, the loudspeaker 13 emits an audible signal each time the limit angle fixed as the extension threshold is reached, which encourages the patient to pay attention and correct himself. -)
The knee recurvatum rehabilitation program includes 2 more, a calculation of the number of times the extension threshold is exceeded during a session or per unit of time, for example per minute. If this number is less than 10, the speech synthesizer announces the number of overruns reached. If the number is greater than 10, the loudspeaker emits a sound signal whose duration is proportional - to the number of overshoots.

 The periods during which the switch 9 is closed, that is to say the duration of the heel's contact with the ground, is also recorded during each rehabilitation session.

 At the end of the session, the curve representing the signal delivered by the potentiometer 5 is plotted by a graphic printer 20, that is to say the curve representing the angle of flexion of the leg and, on the same graph, the heel rest time on the ground. These graphs drawn on paper allow the rehabilitator to accurately assess the patient's condition and compare with the results achieved at the end of the previous sessions to judge the real development.

 Figures 3 and 4 show two flexion curves of the leg recorded on the same patient. These figures represent the time between zero and 10 seconds on the abscissa and on the ordinate the signal delivered by the potentiometer which represents the angle of flexion of the leg between zero and 900, the zero having been determined by a prior calibration as indicated. above.

 Figures 3 and 4 show results obtained five weeks apart at the rate of three rehabilitation sessions of 3 minutes each, for five days each week, by a patient with hemiplegia due to a brain tumor.

 During these sessions, the patient was warned by an audible signal each time the knee extension reached a threshold. This threshold was not changed during successive sessions.

 Figure 3 shows a recording taken at the start of the first week. We see that the patient's leg reaches the maximum extension taken as zero reference.

 Figure 4 shows a recording taken at the end of the fifth week. We see that the flexion of the leg remains greater than 150, that is to say that the recurvatum dyù knee has been corrected. Experience shows that this correction is lasting.

 When it is desired to make, during a reeducation session, electrical stimulation, for example stimulation of the levator muscles of the foot by means of an ambulatory stimulator 11 and transcutaneous electrodes 12a, 12b, one loads into the memory long live 15 a stimulation program.

 By means of the keyboard 7, three digital data are introduced into the random access memory 15: a reference angle a of the leg flexion, for example a = 150, a delay r in tenths of a second which elapses between the passage of the leg, in the direction of decreasing angles, by the reference angle and a duration t in tenths of a second which corresponds to the duration of the electrical stimulation.

 An apparatus according to the invention makes it possible to adapt these three data to a patient and to modify them during successive rehabilitation sessions, so that the stimulation occurs at the time and during the most effective duration.

 Figure 5 shows a curve plotted by the graphic printer. The abscissa represents time for ten seconds.

The curve C1 represents the signal delivered by the potentiometer, that is to say the flexion angle of the leg in degrees brought back to a zero reference obtained by a prior calibration.

 The horizontal dotted lines L1 located at the top of the figure represent the closing times of the microswitch 9, that is to say the durations of pressing the heel on the ground. Lines L2 indicate the periods during which the heel is in the air.

 The horizontal lines S at the bottom of the graph represent the position during the cycle of each step and the duration of the electrical stimulation pulses of the lifting muscles of the foot. The graph also indicates the values of the three parameters introduced into the device at the start of the sessions, namely: a = 15 r = 5 and t = 5, that is to say that the pulses S appear with a delay r of 0, 5 seconds with respect to the passage of the leg through the angle 150, this passage being measured in the direction of the decreasing angles and that they last for 0.5 seconds.

 The foregoing description refers to an apparatus used to record movements and to rehabilitate a patient with impairments in one leg. It is specified that this choice is not limiting and it is possible to construct fe reeducation devices according to the invention making it possible to process the signals delivered by two go niometers and two microswitches in the case of a patient having two deficient legs.

 With regard to stimulation of the lifting muscles of the foot, it is possible to perform two stimulations in steps: one when the foot leaves the ground and one when the foot rests again. It is also possible to stimulate other muscles during each step so as to obtain a gait approaching natural movements.

 Apart from locomotor rehabilitation, an apparatus according to the invention can be used for research in physiology of locomotion or for quantifying locomotor deficiencies by simultaneous recording of the values of the angle of flexion of the leg and of the foot contact with the ground.

 It can also be used in the sports field to improve performance thanks to the possibility of recording using a portable device.

 It can also be used to carry out research in the clinical, neurological or trauma fields.

Claims (9)

 1. Ambulatory electronic apparatus for recording and / or rehabilitation of locomotion, characterized in that it comprises  - an angular sensor (5), placed at the knee of a patient, which delivers an analog electrical signal representing the angle of flexion of the leg;  - an electronic calculation unit carried by the patient, which comprises an interface circuit (18a), which receives the analog signals and which comprises an analog to digital converter which samples the analog signals and converts them into digital values; a microprocessor (14); and a random access memory (15) which stores said digital values;  - a magnetic cassette recorder-player;  - And a keyboard (7) which makes it possible to introduce into said random access memory a program recorded on jet cassette / or digital data.  2. Apparatus according to claim 1, characterized in that it comprises a loudspeaker (13) which emits an audible signal when the knee extension angle exceeds a threshold whose value p-could be modified by means of said keyboard (7).  3. Apparatus according to any one of claims 1 and 2, characterized in that it further comprises a microswitch (9) which is placed in the shoe and which is connected to the analog to digital converter of said circuit d 'interface (18a).  4. Apparatus according to any one of claims 1 to 3, characterized in that it comprises one or more portable devices (11) of functional electrical stimulation which are connected to electrodes (12a, 12b) transcutaneous disposed on a nerve or on a muscle and relays which are controlled by said microprocessor when certain thresholds are exceeded and which control said stimulation devices.  5. Apparatus according to claim 4, characterized in that it comprises two electrodes (12a, 12b), of opposite polarity, which are placed on desmusclesreleveursdu foot or on the external popliteal sciatic nerve which controls these muscles.  6. Apparatus according to claim 5, characterized in that it is programmed to control the stimulation of the levator muscles of the foot, for a duration (t) and with a delay (r) determined relative to the passage of the leg by an angle given flexion (a) and the values of said duration, said delay and said reference angle (a) are programmable from said keyboard.  7. Apparatus according to any one of claims 1 to 5, characterized in that it is associated with a graphic printer (20) to which it is connected after a rehabilitation session and it includes a program which controls printing by The printer of a curve representing the variations of the knee flexion angle.  8. Apparatus according to any one of claims 2 to 7, characterized in that it is programmed to calculate the number of overruns of said extension threshold per rehabilitation session or per unit of time and to issue at the end of the session a audible signal indicating the number of exceedances.  9. Apparatus according to any one of claims 1 J to 8, characterized in that it comprises means making it possible to fix, by means of said keyboard (7), the duration of a rehabilitation session and means for emitting a acoustic signal when the set duration is reached.