End-range Maitland mobilization decreasing pain sensitivity in knee osteoarthritis: randomized, controlled clinical trial

Abstract

BACKGROUND

Pressure pain threshold (PPT) is a widely applied method for measuring the magnitude of increased peripheral and central pain sensitivity causing hyperalgesia in knee osteoarthritis (OA). Although manual therapy techniques effects positively PPT, the effect of end-range Maitland mobilization has not been evaluated in knee OA.

AIM

The aim of this study was to investigate the effect of end-range Maitland mobilization compared to sham manual therapy technique on PPT and function-related measures.

DESIGN

The design of the study was of a randomized, controlled clinical trial.

SETTING

Outpatient setting.

POPULATION

Forty women with moderate-to-severe knee OA.

METHODS

Twenty patients (N.=20) were randomly assigned to Maitland group (MG) and twenty patients (N.=20) to control group (CG). Patients in MG received single end-range Maitland mobilization while patients in CG received sham manual therapy technique. Assessment was performed at baseline, 30 minutes and after 1-week period. Outcome measures were PPT locally at knee and distant at ipsilateral extensor carpi radialis longus muscle, general pain during the previous week using the Visual Analogue Scale (VAS), Timed Up and Go Test (TUG) time associated with pain measured with Numerating Pain Rating Scale (NPRS) and strength of passive resistance of knee at onset of pain.

RESULTS

Despite all outcome measures improved significantly postintervention, no changes were detected after 1-week period compared to postintervention in MG. No change of outcome measures was found also postintervention and after 1-week period compared to postintervention in CG. All postintervention results showed significant improvement in between-group comparison in favor of MG. However, after 1-week period, only strength of passive resistance revealed significant difference in between-group comparison in favor of MG (P<0.001).

CONCLUSIONS

Although end-range Maitland mobilization has an immediate effect on decreasing peripheral and central pain sensitivity and improving function-related measures in knee OA, these changes may not cause clinically relevant effect based on data measured after 1-week period.

CLINICAL REHABILITATION IMPACT

Investigating the time-course of end-range Maitland mobilization for determining the optimal treatment frequency during rehabilitation is suggested in knee OA.

Knee osteoarthritis (OA) is the most common form of arthritis contributing to a major cause of disability worldwide.¹ Albeit knee OA is characterized by several symptoms, pain is the most dominant patient-reported feature affecting quality of life too.² Emerging evidence suggests that altered pain processing in knee OA within the peripheral and central nervous system may be present leading to hyperalgesia in knee OA.^{3, 4} Peripheral nociceptors may be sensitized by, e.g. the inflamed synovium and the damaged subchondral bone leading to increased deep mechanical peripheral pain sensitivity.^{5, 6} Continuous and intense nociceptive input from the damaged knee in OA may drive central pain sensitivity^7-9 and may therefore play an important factor in the maintenance and severity of pain serving as the transition from acute to chronic pain. Out of several quantitative sensory testing methods measuring somatosensory function in musculoskeletal disorders, pressure pain threshold (PPT) is a simple and commonly applied method for evaluating pain sensitivity. While an externally controlled, innocuous mechanical stimuli is applied, patients’ responses can be assessed at the affected knee and at a distant location for identifying localized and widespread changes in the magnitude of peripheral and central pain sensitivity, respectively.¹⁰ Lower PPT represents increased sensitivity to pain, while higher PPT suggests decreased sensitivity of pain and therefore increased pain threshold. Many trials have presented enhanced mechanical pain sensitivity in knee OA compared to healthy controls.^{11, 12} The influence of biomechanical, neurophysiological, psychological, and nonspecific patient factors as treatment mediators and/or moderators provides information related to the process and potential mechanisms by which MT may be effective. The mediating mechanisms of MT on experiencing pain likely combine biomechanical and neurophysiological effects.¹³ Positive results of different manual therapy techniques on decrease of peripheral and central pain sensitivity have been already reported in knee OA.^{14, 15} However, Maitland manual therapy among other manual therapy techniques could be an appropriate treatment modality for lowering the pain sensitivity in knee OA. Accessory techniques performed with Grade I and II and physiological techniques performed with Grade II in not end-range position of the joint aim to alleviate pain alone. Accessory and physiological techniques performed with Grade III and IV in end-range position of the joint improve alongside alleviation of pain additionally the extensibility of periarticular tissues.¹⁶ To date, Moss et al. demonstrated the immediate effect of accessory Maitland mobilization performed with Grade II on reduction of pressure hyperalgesia in knee OA.¹⁷ Moreover, Courtney et al. presented also after accessory Maitland mobilization performed with Grade II decrease of peripheral pain sensitivity immediately and after 1-week period too in knee OA.¹⁸ However, no study has investigated the effect of end-range Maitland mobilization on deep mechanical pain sensitivity immediately and after 1-week period in knee OA yet. As end-range Maitland mobilization is effective in stretching of periarticular tissues,^{19, 20} further decrease of pain perception of local periarticular tissues and consequently lowering of centrally mediated widespread pain sensitization could be expected after applying it. Moreover, clinical studies revealed correlation between PPT and subjective pain^{21, 22} giving an indication for measuring both outcomes after end-range Maitland mobilization. In addition, as accessory Maitland mobilization performed with Grade II produces initial effect on different function-related measures,^{17, 23} a comprehensive examination may provide further meaningful information of end-range Maitland mobilization immediately and after 1-week period in knee OA. Therefore, the results of both follow-ups may further serve as a basic for determining the optimal treatment frequency of end-range Maitland mobilization during rehabilitation in knee OA. Therefore, the primary aim of the present study was to investigate end-range Maitland mobilization compared to sham manual therapy technique on peripheral pain sensitivity immediately and after 1-week period in knee OA. As secondary outcomes, central pain sensitivity and some function-related measures were also evaluated. The hypothesis was that end-range Maitland mobilization could immediately decrease both peripheral and central pain sensitivity, improve functional status and maintain these effects after 1-week period compared to sham manual therapy technique in knee OA.

Materials and methods

Patients

Patients enrolled in the study met the clinical classification criteria of knee OA according to the American College of Rheumatology^{24, 25} and were categorized as end of range problem based on Maitland manual therapy.¹⁶ Inclusion criteria were female patients aged between 60 and 80 years, uni/bilateral moderate-to-severe symptomatic tibiofemoral knee OA with radiographic evidence of Kellgren-Lawrence scale 2 or 3,²⁶ pain during weight-bearing activities during the last 6 months, at least 90° knee flexion correlating with Kellgren-Lawrence scale 2 and 3,²⁷ and sufficient mental status measured by the state-trait anxiety inventory.²⁸ Exclusion criteria were acute inflammation of the knee, total knee replacement in the opposite side, severe degenerative lumbar spine disease (e.g., spondylolisthesis), systemic inflammatory arthritic or neurological condition, physiotherapy/balneotherapy attendance or manual therapy within 3 months, intraarticular injections in the prior 12 months, use of walking aid, contraindication for manual therapy, complex regional pain syndrome or cognitive impairment. Patients participating in the trial obtained written informed consent. The trial was approved by the Regional Research Ethics Committee of the Medical Center in Pécs (protocol number: 8086 – PTE 2019; chairperson: György Kosztolányi, MD; date of approval: 29.11.2019).

Study design and protocol

Randomized, controlled, patient-blinded clinical trial was conducted in a physical therapy room at the Balneology Department of the Zsigmondy Vilmos Spa and Balneological Hospital of Harkány according to the CONSORT guidelines²⁹ in accordance with the Declaration of Helsinki. The trial protocol was registered at ClinicalTrials.gov (N. NCT04273906). Patients were recruited through a Hungarian health information technology. Patients with knee OA, whose disease stage met the inclusion criteria, were retrieved from the hospital database. Two investigators (PT and NN) phoned patients screening for further eligibility and asking them for participating in the study between December 2019 and end of January 2020. Then, the selected patients were examined in a personal consultation. Finally, forty patients were selected and enrolled in the trial. Twenty patients (N.=20) were randomly assigned to Maitland group (MG) and twenty patients (N.=20) to control group (CG). Patients in MG received end-range Maitland mobilization while patients in CG received sham manual therapy technique. Assessment of patients was conducted prior, 30 minutes and 1 week after the applied intervention¹⁸ in January 2020 by an investigator (MP). As part of the patient assessment, knee synovitis, other signs of inflammation, and the extent of knee flexion were examined, then were the outcome measures performed. Evaluation of results of assessment was carried out by the same assessor (MP). Patients remained blinded to group allocation throughout the trial. The flow diagram of the trial is displayed in Figure 1.

Figure 1.

—Flow diagram of the trial.

Sample size calculation

Sample size calculation was conducted using Stata 15.0. Based on the trial of Paolillo et al.,³⁰ the effect size of PPT was 13. For observing this relevant difference between groups with 5% alpha level and 90% power, 17 patients were required for both groups. For allowing some dropouts, 20 patients were finally selected for both groups.

Randomization

Randomization procedure was conducted by single randomization. Allocation of the selected 40 patients was implemented by computer-generated random characters (A and B) produced only for randomization purpose on a 1:1 ratio with Microsoft Excel RAND function (Microsoft Corp., Redmond, WA, USA). An independent investigator performed the randomization, placed these random characters into sealed opaque envelopes and provided the group allocation to investigator (MP). Envelopes were opened only in the presence of the patient.

Interventions

End-range Maitland mobilization was performed individually in flexion and extension end-range of the tibiofemoral joint. Accessory technique with Grade III or IV was performed in an oscillatory way depending on the level of tolerance and pain of the patient.³¹ Patients laid down supine on the plinth with the knee positioned to its actual end-range. That accessory technique was used, which reproduced the knee pain or was the most limited.¹⁵ The performed manual contact reproduced the hand position of the mobilization precisely by movement of the therapist’s body without performing another movement. End-range Maitland mobilization was performed at the rate of 1 oscillation in every 1 or 2 second twice for 3 minutes with 30 seconds rest between mobilizations as described by Courtney et al.¹⁸ Sham manual therapy technique was performed on the tibia in both end-range positions of the knee. It consisted of hands-on cutaneous input technique without performing any movement of the knee. Sham manual therapy technique was also performed twice for 3 minutes with 30 seconds rest intervals. Only the most symptomatic knee was mobilized in case of bilateral knee OA, due some patients had unilateral knee OA, some patients had bilateral knee OA with unilateral knee pain but none of them had the same pain in both knees. A trained and classified Maitland manual therapist (MP) with 6 years of clinical experience performed both interventions individually in a physical therapy room at the Balneology Department. No confounding factors or adverse events were observed after interventions or during the following week resulting in patients drop out.

Outcome measures

Pain-related measures

Local PPT

Peripheral pain sensitivity was assessed with the digital hand-held pressure algometer (FPIX 50, Wagner Instruments, Greenwich, CT, USA)³² with a 1-cm² circular probe area on eight different locations around the symptomatic knee as described by Paollili et al.³⁰ These locations included: 1) 2 cm distal to the inferior medial edge of the patella; 2) 2 cm distal to the inferior lateral edge of the patella; 3) 3 cm lateral to the midpoint on the lateral edge of the patella; 4) 2 cm proximal to the superior lateral edge of the patella; 5) 2 cm proximal to the superior edge of the patella; 6) 2 cm proximal to the superior medial edge of the patella; 7) 3 cm medial to the midpoint on the medial edge of the patella; and 8) center of the patella. Patients were asked to sit on a chair while the algometer was placed and applied perpendicular to the skin. Pressure was gradually increased over the marked locations until patients indicated verbally that the sensation became painful.³³ Measurements were taken three times for each location with 20 seconds rest interval between each measurement.³³ The force of pressure was expressed in Newton/cm² (N/cm²). The mean of the three measurements for each location and further the mean of the summarized values was calculated for further statistical analysis.

Distant PPT

Central pain sensitivity was assessed at the ipsilateral m. extensor carpi radialis longus (ECRL) muscle 5 cm distal from the lateral epicondyle of humerus²² with the same algometer and procedure, as used during the measurement and calculation of values of local PPT.

General pain

Perceived general pain intensity during the previous week was evaluated with the 100 mm Visual Analogue Scale (VAS).³⁴ Patients had to rate their pain intensity on a horizontal line with terminal descriptions of “no pain” and “worst imaginable pain.” General pain was determined only prior the treatment session and after 1-week period.

Pain during dynamic balance

Perceived pain intensity during dynamic balance was evaluated using the Numerating Pain Rating Scale (NPRS).³⁵ Patients had to rate their pain intensity on an 11-point scale ranging from 0 “no pain” to 10 “worst imaginable pain.”

Function-related measures

Dynamic balance

Dynamic balance of patients was measured with the Timed Up and Go Test (TUG).³⁶ Patients were instructed to rise from a standard armchair, walk 3 meters, turn and walk back to the chair and sit down. Patients were asked to perform the test by their own pace. The time completing the test was recorded in seconds using a stopwatch.

Strength of passive resistance

Strength of passive resistance at the degree of passive knee flexion at the onset of pain relates to a method measuring pain-free knee range of motion and the degree of resistance of connective tissues during passive knee flexion at the same time. This test was implemented in prone position. The patient lied comfortable on the plinth with the thigh placed in neutral position. As the knee flexion increases, the tension in the connective tissues surrounding the knee increases, resulting in enhanced passive resistance. During the test, knee was passively flexed to the onset of pain where the degree and the associated strength of passive resistance was measured with the full-circle 1°-increment plastic standard long-arm extendable goniometer (Elite Medical Instruments, USA) with a moveable arm³⁷ and with hand-held dynamometer placed to the tibia 3 cm proximal from the talocrucal joint (MicroFET 2, Hoggan Health Industries Inc., Draper, UT, USA), respectively. After intervention, the knee was placed passively into the degree of knee flexion measured preintervention and the actual passive strength of resistance was re-evaluated. The change of passive strength expressed in Newton (N) was calculated for further analysis. Although measuring the strength of passive resistance in this way is not widespread, its implementation may reveal a few facts about knee function. Because performing this test is simple to implement, it can also be used in clinical practice in the future.

Statistical analysis

Distribution of the measured variables was examined with Shapiro-Wilk normality test. Independent samples t-test and Mann-Whitney U Test was used depending on the distribution to compare demographical data and baseline values of both groups. Wilcoxon signed-rank test was used to compare changes within-group measurements. Mann-Whitney U Test was used to compare differences between-group measurements. Analysis was carried out with IBM SPSS Statistics 25.0 (IBM Corp., Armonk, NY, USA). Results of demographical data are presented as mean±standard deviation and results of outcome measures are presented as median and interquartile range (IQR). Significance level was set at P<0.05.

Data availability

Datas of patients can be found in the Department of Balneology, Zsigmondy Vilmos Spa and Balneological Hospital of Harkány. The datas associated with the paper are not publicly available but are available from the corresponding author on reasonable request.

Results

All 20 patients in both groups completed the trial with no patients drop out of either group. No significant difference was found between baseline characteristics of patients in both groups (Table I).

Table I. —Demographic characteristics of patients in both groups.

Characteristics	MG (N.=20)	CG (N.=20)	P
Age (years)	70.4±5.95	66.9±4.98	0.051
Body height (m)	1.64±0.05	1.59±0.06	0.023
Body weight (kg)	80.25±9.06	79.7±15.75	0.893
BMI (kg/m2)	29.07±5.33	30.95±5.13	0.262
Affected side (left/right)	13/7	11/9
Severity of knee OA (K-L scale)
2(%)	11 (55)	9 (45)
3(%)	9 (45)	11 (55)
Comorbidity (number of patients)
Heart condition	19	12
Gynecological condition	1	3
Musculoskeletal condition	3	4
Other diseases	5	6
Time from onset of symptoms (years)	9.00 (4.50-20.00)	9.00 (5.00-20.00)	0.925
Location of knee pain (number of patients)
Medial	15	16
Lateral	4	7
Anterior joint line	3	2

Data are mean±standard deviation except Time from onset of symptoms as median(lower IQR-upper IQR). MG: Maitland group; CG: control group; BMI: Body Mass Index; knee OA: knee osteoarthritis; K-L scale: Kellgren-Lawrence Scale.

No significant differences were also found between outcome measures of both groups at baseline except strength of passive resistance (P<0.001) (Table II).

Table II. —Results of secondary outcomes.

	MG (N.=20)	P	CG (N.=20)	P	Between-group comparison (P value)
Distant PPT (N/cm2)
Baseline	31.65 (19.65-36.60)		21.90 (13.30-31.35)
Postintervention	38.10 (28.45-50.15)	<0.001*	21.40 (10.59-30.00)	0.151	<0.001*
After 1-week period	29.95 (24.40-42.90)	0.198	20.35 (12.64-29.70)	0.507	0.383
General pain VAS
Baseline	65.00 (44.00-70.00)		66.00 (53.50-68.00)
After 1-week period	54.00 (30.50-72.00)	0.147	65.00 (54.50-68.50)	0.519	0.461
NPRS
Baseline	4.50 (2.50-7.00)		4.00 (2.00-6.00)
Postintervention	3.00 (0.50-5.00)	0.005*	3.50 (2.80-6.80)	0.305	0.006*
After 1-week period	4.00 (1.00-6.00)	0.153	3.50 (2.00-6.00)	1.000	0.429
TUG (sec)
Baseline	14.25 (12.60-20.10)		12.95 (11.80-18.05)
Postintervention	13.85 (11.25-15.00)	<0.001*	12.80 (11.35-17.35)	0.085	0.015*
After 1-week period	12.25 (10.45-14.90)	0.056	12.60 (11.00-16.45)	0.687	0.076
Degree of passive knee flexion
Baseline	110.00 (86.00-117.00)		99.00 (87.50-114.00)
Strength of passive resistance (N.)
Baseline#	28.65 (21.10-33.30)		17.05 (14.20-21.10)
Postintervention	19.30 (14.20-23.50)	<0.001*	16.25 (14.60-22.80)	0.569	<0.001*
After 1-week period	25.20 (16.65-35.30)	0.054	22.05 (15.50-31.10)	0.053	<0.001*

Data are median (lower IQR-upper IQR). MG: Maitland group; CG: control group; ECRL: distant; PPT: pressure pain threshold of the m. extensor carpi radialis longus muscle; N/cm²: Newton/cm²; general pain; VAS: General pain intensity measured with Visual Analogue Scale; TUG: Timed Up and Go Test; sec: secundum; NPRS: Numerating Pain Rating Scale; N: Newton. ^#Significant baseline difference between MG and CG; *statistically significant.

Local PPT

Local PPT increased significantly postintervention in MG, but no postintervention change was seen in CG. Most importantly, significant difference was found comparing postintervention data of MG and CG. However, local PPT presented no change after 1-week period compared to postintervention in within-group and between-group comparison. Change of local pressure pain threshold between groups is presented in Figure 2.

Figure 2.

—Change of local pressure pain threshold between groups.

Distant PPT

Distant PPT increased significantly postintervention in MG, but no postintervention change was found in CG. Most importantly, significant difference was presented in between-group comparison of postintervention data in favor of MG. However, distant PPT presented no change after 1-week period compared to postintervention in within-group and between-group comparison (Table II).

General pain VAS

Both within-group and between-group comparison revealed no change in general pain VAS after 1-week period in favor of MG (Table II).

Pain during TUG

NPRS decreased significantly postintervention in MG, but no change was revealed in CG. Especially, between-group comparison of postintervention data presented significant difference in favor of MG. Although, no difference was revealed after 1-week period in both within-group and between-group comparison (Table II).

Dynamic balance

TUG decreased significantly postintervention in MG, but no postintervention change was seen in CG. Most importantly, significant difference was found in between-group comparison of postintervention data in favor of MG. However, TUG presented no change after 1-week period compared to postintervention in within-group and between-group comparison (Table II).

Strength of passive resistance

Strength of passive resistance decreased significantly postintervention in MG, but no postintervention change was seen in CG. Most importantly, between-group comparison revealed significant difference (P<0.001) in favor of MG in both postintervention data and after 1-week period data too. Strength of passive resistance presented no change after 1-week period compared to postintervention in CG (Table II).

Discussion

Pain-related measures

Despite the immediate increase of local and distant PPT in MG attributed to local, segmental and supraspinal pain inhibitory mechanism,^{13, 38} single end-range Maitland mobilization may not lead to clinically relevant decrease of peripheral and central sensitization measured after 1-week period in knee OA. Therefore, in one hand, single end-range Maitland mobilization may be performed rather prior physiotherapy treatment in practice. As alleviation of pain may be achieved immediately, active strengthening and stabilizing exercises could be performed more effectively resulting in improved function. However, it would be interesting to investigate the time-course of a single end-range Maitland mobilization on peripheral and central sensitization in knee OA. In other hand, performing end-range Maitland mobilization more than once a week is suggested for achieving long-term effect. Alkhawajah et al. presented immediate increase of both local and distant PPT after single end-range Mulligan mobilization in knee OA.³⁹ Furthermore, Lluch et al. showed also initial reduction of local and distant pressure hyperalgesia after end-range Maitland mobilization in overhead athletes with chronic shoulder pain.⁴⁰ Lopez-Lopez et al. revealed immediate reduction of peripheral and central sensitization after end-range Mulligan mobilization in chronic neck pain.⁴¹ However, neither trial investigated the effect of a single end-range mobilization on local and distant PPT after 1-week period. Noticeably, Courtney et al. showed in their study increase of local and distant PPT after not end-range mobilization both immediately and after 1-week period;¹⁸ however, patients in that study were investigated for ineffective central pain inhibition, the so called condition pain modulation, which was not examined in the present study. Moreover, de Miguel et al. showed that end-range Kaltenborn mobilization performed every day for 3 consecutively days increased both local and distant PPT in hip OA.³³ Therefore, it would be advisable to conduct further trials investigating the effect of a single and several times per week as well performed end-range Maitland mobilization on pressure hyperalgesia in knee OA and in several conditions too. The observed meaningless difference revealed in general pain VAS in MG in contrast to CG after 1-week period might be attributed to local and central pain sensitivity almost reaching baseline values. Previous studies focused mainly on investigating of the immediate effect of single mobilization performed in end-range and not end-range position during function. Moss et al. demonstrated the immediate effect of accessory Maitland mobilization performed with Grade II on function-related pain in knee OA.¹⁷ Furthermore, Alkhawajah et al. applied end-range Mulligan mobilization suggesting alleviation of pain during function for at least 2 days.³⁹ In additon, Lluch et al. showed initial reduction of self-reported resting shoulder pain after end-range Maitland mobilization in overhead athletes with chronic shoulder pain.⁴⁰ Therefore, comparison for revealing the hypoalgesic effect of single end-range Maitland mobilization in general may be challenging. Consequently, it would be advisable to perform end-range Maitland mobilization several times for alleviating general pain measured after 1-week period in further trials and in clinical practice as well. Despite the immediate perceived decrease of NPRS in MG attributed to the already discussed local, segmental and supraspinal pain inhibitory mechanism,^{13, 38} single end-range Maitland mobilization may not produce clinically relevant alleviation of pain measured after 1-week period during function too. Moss et al. presented in their study the immediate decrease of pain intensity during TUG after accessory Maitland mobilization performed with Grade II in knee OA.¹⁷ Bhagat et al. revealed immediate decrease of pain intensity during knee movement after end-range Mulligan mobilization in knee OA.⁴² Hauswirth et al. showed immediate alleviation of pain during shoulder end-range position after end-range Maitland mobilization performed on the neck in postoperative arthroscopy patients.⁴³ De Miguel et al. presented decrease of pain intensity during physical function after 3 consecutive days of 3-times performed end-range Kaltenborn mobilization in hip OA.³³ However, similarly to the previously discussed pain-related measures, no study has measured pain intensity after 1-week period during knee function. As patients use their knees almost constantly during the day, repetitive passive stretching may be required for alleviation of pain during movements; however, local and central pain sensitivity may be decreased as a consequence. Therefore, the effect of sensitization on pain intensity during physical activity needs further investigation.

Function-related measures

Despite the immediate decrease of TUG time in MG attributed to the pain inhibitory mechanisms discussed previously,^{13, 38} single end-range Maitland mobilization produced no meaningful improvement during function-related task measured after 1-week period. Previous suggestions revealed joint mobilization performed both in end-range and not end-range enhances immediately motor activity giving an indication of centrally mediated response.^{17, 42} Moreover, this effect may reflect on reversal of reflex pain inhibition consequently resulting in initial improvement of physical function.⁴⁴ Alkhawajah et al. presented immediate decrease of TUG time 2 days after single end-range Mulligan mobilization performed in knee OA.³⁹ In addition, de Miguel et al. presented decrease of pain intensity during physical function after 3 consecutive days of 3-times performed end-range Kaltenborn mobilization in hip OA.³³ However, no study has investigated the immediate effect of a single joint mobilization performed in end-range or not end-range on physical function after 1-week period. Therefore, performing further trials investigating end-range Maitland mobilization on decrease of TUG time is suggested in knee OA. Interestingly, as muscle fibers are elongated alongside periarticular tissues, facilitation of muscle spindles may lead to improved contraction of muscles⁴⁵ and therefore increased motor control. As a consequence, the connection between decreased peripheral and central pain sensitivity and contraction of muscle spindles on motor function needs to be investigated in more details. The immediate and even after 1-week period observed decrease of strength of passive resistance in MG could be attributed to improvement of extensibility of periarticular tissues.^{13, 46} As the pain increases during examination of passive joint mobility, involuntary muscle spasm may occur leading to further pain cycle and the increase of resistance.¹⁵ Thus, measurement of strength of passive resistance was performed only on the onset of knee pain refering to passive joint mobility examination. Lopez-Lopez et al. revealed immediate improvement of passive neck mobility after end-range Mulligan mobilization in chronic neck pain.⁴¹ Moreover, Hauswirth et al. showed immediate increase of active shoulder mobility after end-range Maitland mobilization performed on the neck in postoperative arthroscopy patients.⁴³ In addition, Lluch et al. presented immediate increase of active shoulder mobility after single end-range Maitland mobilization performed in overhead athletes with chronic shoulder pain.⁴⁰ Therefore, no study has investigated the effect of a single end-range Maitland mobilization on passive joint mobility after 1-week period. Interestingly, strength of passive resistance was even greater at baseline in MG compared to CG, but strength of passive resistance increases simultaneously with increase of knee flexion range. Therefore, single end-range Maitland mobilization may be effective in decrease of resistance of periarticular tissues measured in painfree knee flexion range even in knee OA with greater periarticular resistance. Due decrease of strength of passive resistance remained after 1-week period, single end-range Maitland mobilization could be a clinically relevant intervention in knee OA. Even treating only one, the more painful knee, it becames less painful and symptomatic.Therefore, it could have been flexed and used more sufficiently during walking and in divergent changing position, thus improving patients overall daily activity level. It is general observation that experiencing and perceiving of pain itself associates strongly with the quality of life. Moreover it effects the activity of daily life, which is also strongly associated with quality of life.⁴⁷ For example, the very common used SF-36 test has bodily pain and physical functioning sections (two sections from eight total). Further studies may reveal the more accurate effect of single end-range Maitland mobilization on quality of life in knee OA.

Limitations of the study

The results may have been more representative for knee OA population in the case of recruiting male patients in the study too. Moreover, lack of assessors and operators blindness could have resulted in performance bias. Furthermore, follow-up results after 1-week period need to be handled cautiously. In fact, patients were instructed to maintain their daily life activities and advised to avoid any kind of treatment; however, no supervision was applied during the 1-week period.

Conclusions

In conclusion, the present study showed that single end-range Maitland mobilization decreased immediately both peripheral and central pain sensitivity, TUG time, NPRS and strength of passive resistance in knee OA. Furthermore, end-range Maitland mobilization provided superior effect on decrease of strength of passive resistance even after 1-week period in knee OA. Therefore, single end-range Maitland mobilization could lead to clinically relevant effect in improving of extensibility of periarticular tissues after 1-week period in knee OA. As consequence, performing end-range Maitland mobilization could be efficient prior physiotherapy treatment. Hence, investigating the time-course of the effect of single end-range Maitland mobilization would be interesting for determining the optimal treatment frequency during rehabilitation in knee OA. In addition, further studies could also focus on investigating the long-term effects of end-range Maitland mobilization on peripheral and central sensitization and function-related outcomes in knee OA.