Effect of a physiotherapy rehabilitation program on knee osteoarthritis in patients with different pain intensities (2024)

Abstract

[Purpose] To examine the effect of physiotherapy rehabilitation program on moderate kneeosteoarthritis in patients with different pain intensities. [Subjects and Methods] Sixtysubjects (37 men and 23 women) with moderate knee osteoarthritis participated in thecurrent study. Randomization software was used to select the participating subjects’numbers from the clinic records. They were classified into three groups according to painintensity: mild, moderate, and severe pain groups. All groups underwent a standard set ofpulsed electromagnetic field, ultrasound, stretching exercises, and strengtheningexercises. Pain intensity, knee range of motion, knee function, and isometric quadricepsstrength were evaluated using the visual analogue scale, universal goniometer, WesternOntario and McMaster Universities osteoarthritis index, and Jamar hydraulic dynamometer,respectively. The evaluation was performed before and after a 4-week rehabilitationprogram. [Results] All groups showed significant differences in pain intensity, knee rangeof motion, isometric quadriceps strength, and knee function. The score change in moderatepain group was significantly greater than those in mild and severe pain groups.[Conclusion] Pain intensity is one of the prominent factors that are responsible for theimprovement of knee osteoarthritis. Consequently, pain intensity should be consideredduring rehabilitation of knee osteoarthritis.

INTRODUCTION

Degenerative joint arthritis is the most common joint disorder that is caused bybiomechanical stresses affecting both the articular cartilage and subchondral bone.Degenerative osteoarthritis (OA) is the most common form of arthritis and is a major causeof morbidity and functional limitation, especially in elderly patients1⁾. The incidence of knee OA is expected to increase over thenext decades2⁾. Knee OA is directly relatedto disabilities due to pain, quadriceps dysfunction, and impaired proprioception. Moreover,knee OA is responsible for the impaired ability of the quadriceps muscle to control force inpatients with OA. Nevertheless, exercise therapy is effective in reducing the pain andimproving the function of patients with knee OA3⁾.

Unlike many other pain conditions in which the underlying injury typically heals orresolves, OA is a disease that does not resolve. Thus, OA is typically accompanied bychronic pain. Whether, and to what degree, this ongoing chronic pain (i) plays an importantnociceptive role, (ii) represents maladaptive pain, or (iii) reflects other aspects of thepain experience are not clear4⁾.

Pain is one of the most commonly reported and prominent factors that are responsible forphysical inactivity in patients with knee OA5⁾. This impairment in physical activity associated with knee OA hasimportant implications for aerobic power and cardiovascular health. Hence, patients with OAare at a particular risk of poor health outcomes6⁾. Pain pattern and severity of knee OA as either absent, mild,moderate, severe, or very severe could affect the range of motion (ROM) that involves dailyactivities and quality of life7⁾.

Moreover, muscle weakness in knee OA usually results in joint stiffness and decreasing ROMthat involves daily activities8⁾.Quadriceps muscle impairment in knee OA is well documented in the literature. In addition,the differences in the magnitudes of muscle strength are caused by the differences in thesubjects’ characteristics, OA severity, pain severity, and definition of the controlgroup9^,10^,11⁾. Patients with knee OAexperience chronic form of pain and show a declining ability to use their joints, whichconsequently weakens the muscles. Hence, these destabilise the joints and reduce thephysical functions of patients; further, the motions required for the patients’ dailyactivities become restricted12⁾.

Although pain is a symptom of OA that is present in almost all classification criteria forOA, there is often a discordance between reports of pain and radiologic OA13^,14^,15⁾. It is suggested that this discordanceapplies, in particular, to the less severe grades of knee OA and that pain is more common inmore severe grades of OA (1 and 2)13^, 14⁾. Moreover, Erden et al. reported that painintensity and degrees of inaccuracy of knee joint position sense were positively correlatedat 60° and 90° knee flexions. The relationship between pain intensity and knee jointposition sense is very important for patients with OA in the improvement of rehabilitationprograms16⁾. Given these findings, onlyfew studies have considered pain severity during rehabilitation programs for patients withknee OA. Therefore, the aim of this study was to examine the effect of a physiotherapytreatment program on moderate knee OA with different grades of pain intensity.

SUBJECTS AND METHODS

In this study, 78 patients with moderate bilateral knee OA were identified as potentialparticipants based on the orthopaedic physical therapy clinic records. Seven patients didnot meet the inclusion criteria, and five subjects refused to participate in the study. Atotal of 66 patients were recruited via convenience sampling. The participants wereclassified into three groups according to their pain intensity17⁾: mild pain group (23 subjects), moderate pain group (21subjects), and severe pain group (22 subjects). At the end of the 4-week treatment period,outcome data were available for 20/23 patients in the mild pain group, 20/21 in the moderatepain group, and 20/22 in the severe pain group. Some participants withdrew from the studyand were lost to follow-up. Thus, 60 subjects (37 men and 23 women) participated in thecurrent study. Their demographic data are shown in Table 1.

The inclusion criteria were as follows: age between 45 and 62 years, ≤grade 2 radiographicseverity according to the Kellgren/Lawrence scale18⁾, diagnosis of moderate bilateral knee OA according to the AmericanCollege of Rheumatology criteria19⁾, kneepain for more than 3 months in most days of the week, and patients are not obese. Thecriteria for the stages of knee OA are illustrated in Table 2. Conversely, the exclusion criteria were as follows: inflammatory kneedisorders, metabolic bone disease, history of knee trauma, previous knee surgery, previousintra-joint injection, and use of analgesics in the past 3 months20⁾. Written informed consent was obtained from all subjects.The study was conducted in accordance with the 1975 Helsinki Declaration principles, asrevised in 1996. The study procedures were approved by the institutional review board ofFaculty of Physical Therapy, Cairo University (Approval No. P.T.REC/012/001751).

The intensity of knee pain was evaluated using the visual analogue scale (VAS) after thepatients have remained in a weight-bearing state for 5 minutes (walking or standing)21⁾. The pain level was rated by each patientfrom 0 to 10 cm, where 0 represented ‘no pain’, and 10 represented ‘unbearable pain’. Thepain was also graded as follows: 0 to 4 mm, no pain; 5 to 44 mm, mild pain; 45 to 74 mm,moderate pain; and 75 to 100 mm, severe pain17⁾. Based on these grades, the three groups of knee OA werecreated.

Measurement of active knee flexion ROM: While the patients were lying supine on anexamination table, active knee flexion ROM was measured using a plastic universal goniometerwith 25-cm arms, while the goniometer’s pivot tip was placed on the femur’s lateralepicondyle. The patients maintained maximum flexion of the knee joint with hip flexion. Theangle between the maximum flexion and maximum extension was described as the excursionrange. The range was measured thrice, and the mean value was calculated21⁾.

The patients’ disability was evaluated using the valid and reliable modified WesternOntario and McMaster Universities osteoarthritis index (WOMAC)22⁾. It is a questionnaire that evaluates disabilities inperforming daily living activities. This method is relevant and appreciated for itssimplicity and allows assessment of the patients’ opinions of their functionaldisabilities.

The isometric quadriceps strength was measured using Jamar hydraulic dynamometer(Lafayette, IN 47903, USA). Such a device has been proven to have a good to excellentreliability in different populations23^, 24⁾. The patients were instructed to sit onthe side of the bed with their back flat, arms crossed, hip at 90° flexion, and knee at 30°flexion. After ensuring stabilisation in these steps, the therapist held the dynamometerbetween his hand and the patients’ limb segment. The dynamometer was positioned two fingerwidths above the lateral malleolus on the anterior aspect of the tibia, and the patientswere then instructed to push the dynamometer with their maximum strength for 5 seconds. Themean value of the three repetitions with 2-minute intervals was calculated25⁾.

In this study, the treatment program was firstly initiated for treating knee OA based onthe Battecha and Soliman program26⁾. Allgroups underwent a standard set of pulsed electromagnetic field (PEMF), ultrasound (US), andstretching and strengthening exercises. A PEMF device (ASA/Easy terza series, Italy) wasused to provide electromagnetic therapy. The pulse frequencies were 50 Hz for the solenoidsand up to 100 Hz for the applicators. The solenoid encircled the target limb segment at thelevel of the knee. Each patient was exposed to low-intensity 15 GPMF (Gauss permagneticfield) with a frequency of 50 Hz for 30 minutes per session. Thereafter, a US device (ITO,US/100, Japan) was used to provide deep heating therapy. Continuous US waves with a 1-MHzfrequency and 1-watt/cm² power were applied using a 4-cm²-diameterapplicator. The US therapy lasted for 5 minutes per session27⁾. Both PEMF therapy and US therapy were continued for three sessionsweekly for 4 weeks.

Immediately after PEMF and US application, each patient was asked to perform stretchingexercises and strengthening exercises in the following fixed sequence: hamstrings musclestretching and calf muscle stretching. The physical therapist repeated the passivestretching exercises thrice per session. Each stretch was sustained for 30 seconds, with10-second rest intervals28⁾. After a restperiod of 5 minutes, the patients were asked to perform the following: 1) isometricquadriceps contraction (quadriceps drill) in full knee extension maintained for 5 seconds,followed by a 5-second rest; the exercise was performed for 20 repetitions per session29⁾; and 2) straight leg raising exercise in acrock lying position (the patients were asked to tense the quadriceps muscle, elevate thelimb to 45° and maintain it for 6 seconds, and lower the limb slowly and then relax for 6seconds; the exercise was performed for three sets of 10 repetitions per session)28⁾. Both stretching and strengtheningexercises were performed for three sessions weekly for 4 weeks. The evaluation and treatmentprocedures were done for the patients by the same therapist before and after the treatmentperiod. They were instructed to maintain their activity levels during the study period30⁾.

Data were analysed using the Statistical Package for Social Sciences (IBM Corp.: Armonk, NYUSA) version 20.0. A one-way analysis of variance was used to compare the effect of thephysical therapy treatment on the VAS score, knee ROM, quadriceps strength, and WOMAC scoreamong the three groups with knee OA. Score changes were also calculated. The level ofsignificance was set at p<0.05.

RESULTS

The descriptive statistics of the VAS score, knee ROM, quadriceps strength, and WOMAC scoreof the three groups are presented in Table3. The pre-intervention VAS score of the mild pain group was lower than those ofthe moderate and severe pain groups (p=0.001), and that of the moderate pain group was lowerthan that of the severe pain group (p=0.001). There was a significant reduction in painintensity owing to the interventions in the three groups (p=0.001). The post-interventionVAS score of the mild pain group was significantly lower than those of the moderate andsevere pain groups (p=0.001); further, the post-intervention VAS score of the moderate paingroup was significantly lower than that of the severe pain group (p=0.001).

The pre-intervention ROM of the mild pain group was greater than those of the moderate andsevere pain groups (p=0.001), without a significant difference between the pre-interventionROMs of the moderate and severe pain groups (p=0.063). There was a significant improvementin the ROM owing to the interventions in the three groups (p=0.001). The post-interventionROM of the mild pain group was significantly greater than those of the moderate and severepain groups (p=0.008 and 0.001, respectively); moreover, the post-intervention ROM of themoderate pain group was significantly greater than that of the severe pain group(p=0.002).

The pre-intervention isometric quadriceps strength of the mild pain group was greater thanthose of the moderate and severe pain groups (p=0.019 and 0.001, respectively), without asignificant difference between the moderate and severe pain groups (p=0.137). There was asignificant improvement in the quadriceps strength of the three groups (p=0.001, 0.001, and0.004, respectively). There was no significant difference between the post-interventionquadriceps strength of the mild and moderate pain groups (p=0.098). The post-interventionquadriceps strength of the mild and moderate pain groups was significantly greater than thatof the severe pain group (p=0.001 and 0.012, respectively).

The pre-intervention WOMAC score of the mild pain group was lower than those of themoderate and severe pain groups (p=0.001), and that of the moderate pain group was lowerthan that of the severe pain group (p=0.001). There were significant improvements in theWOMAC scores owing to the interventions in the three groups (p=0.001). The post-interventionWOMAC score of the mild pain group was significantly lower than those of the moderate andsevere pain groups (p=0.001), and that of the moderate pain group was significantly lowerthan that of the severe pain group (p=0.010).

The VAS score, knee ROM, and WOMAC score changes in the moderate pain group weresignificantly greater than those in the mild and severe pain groups (p=0.001, 0.001, 0.026,0.013, 0.016, and 0.001, respectively). In the same context, there was no a significantdifference between the mild and severe pain groups (p=0.064, 0.784, and 0.143,respectively).

There was no significant difference in the quadriceps strength score changes among themild, moderate, and severe pain groups (p=0.203, 0.290 and 0.350, respectively). However,the score change in the moderate pain group was significantly greater than that in thesevere pain group (p=0.030).

DISCUSSION

To the best of our knowledge, this is the first study to classify patients with moderateknee OA according to their pain intensity. The results of this study support the hypothesisthat a physiotherapy treatment program has different effects in patients with moderate kneeOA with different grades of pain intensity, indicating that the magnitude of pain is one ofthe prominent factors that are responsible for the improvement of knee OA. However, theseresults are not supported by the findings of Külcü et al. who reported that there is norelationship between VAS scores and regular physical activity habit and symptom duration inpatients with knee OA31⁾.

The patient classification completely depended on the pain intensity, since many previousstudies have shown that there is a discordance in the relationship between pain andradiologic OA. There are patients with a Kellgren/Lawrence grade of 3 or 4 for knee OAwithout any pain in the knee13^,14^,15⁾. For example,29.9% of patients with Kellgren/Lawrence grade 2 and 64.1% of those with Kellgren/Lawrencegrade 3 in the knee in an open population study experienced pain at some points32⁾.

In the pretreatment condition, it was observed that the patients with knee OA with moderateand severe pain showed significant declines in the knee ROM, isometric quadriceps strength,and level of functional performance, which may be due to the level of pain that resulted inthe weakening of muscle strength, instability of the knee joint, and decreased physicalfunction33⁾. Moreover, the impairmentsof muscle activation are magnified in subjects with knee OA ranging from 8 to 25% inpopulations of varying disease severities34⁾. Reduced voluntary activation of the muscles and decreasedcontractile rates are meaningful as these explain the strength decline and changes in musclesize35⁾, which were experienced by thepatients with knee OA with moderate and severe pain in the current study. However, a recentstudy discovered that pain did not influence the thigh muscle electromyogram (EMG)amplitudes or proprioceptive acuity in patients with mild and moderate knee OA during astair climbing task36⁾.

The rehabilitation program decreased the pain intensity and improved the knee ROM,isometric quadriceps strength, and level of functional performance in all knee OA groups. Inaddition, it was clear that the rehabilitation program had more drastic effects in themoderate pain group. Thus, the levels of improvement in the moderate pain group weresuperior to those in the other groups in all measurement outcomes. The compatibility of theresults of the VAS and WOMAC is consistent with the findings of Riddle and Stratford whoconcluded that the WOMAC scores are most strongly associated with pain intensity in patientswith unilateral and bilateral pain37⁾.

The significant improvement in the muscle strength of the three groups might be explainedby the findings of Lewek et al. who reported that the arthrogenic inhibition of thequadriceps muscles of patients with knee OA may be corrected using exercise training34⁾. Moreover, the results of the currentstudy are in line with the findings of Knoop et al. who reported that all grades of knee OAseverity can achieve improvement in pain and functional performance after an exercisetherapy program38⁾. However, it should benoted that this study included an exercise program only, which was applied in patients withknee OA with different grades (mild, moderate, and advanced knee OA); conversely, thecurrent study included patients with moderate knee OA only, and the rehabilitation programincluded stretching exercises, PEMF, and US. The difference in the intervention and patientcharacteristics could explain the greater improvement in the moderate pain group than in thesevere pain group.

The lesser improvement level in the severe pain group in all outcome measures may beexplained by the greater inactivity caused by the higher pre-intervention pain levelsexperienced by the patients in this group, which had profound adverse effects on skeletalmuscle function and metabolism in terms of weakness and atrophy39⁾. In addition, the knee extensors have a prominent role inresisting gravity; they undergo a greater magnitude of weakness and atrophy than othergroups of muscles during inactivity40⁾.

Conversely, the findings of this study revealed a trend toward greater improvements in themoderate pain group, which can be explained by the greater reduction in the score change inthe pain in this group. In the same circumstances, the reduction of pain can improve thelevel of function, ameliorate physical impairment41⁾, and reduce the restriction of movements (knee ROM) as a protectivemechanism in patients with knee OA42⁾. Inaddition, the chronic form and level of pain can result in muscle weakness, and it seemedthat the greater pain reduction and strengthening exercises in this group were responsiblefor improving the isometric quadriceps strength33⁾.

This study has several limitations. Firstly, it did not have a control over the dailyactivities of the patients. Secondly, the long-term effects of this treatment were notidentified. Thirdly, the outcome measures of the study did not involve functional tests,such as the 6-minute walk test. Further research studies with longer durations evaluatingthe effects of physiotherapy rehabilitation programs should be conducted on patients withknee OA, especially those with severe pain. Finally, further studies are needed to examinethe effects of rehabilitation programs on the hip and ankle joints of patients with OA withdifferent degrees of pain, since previous studies have reported that examination of the hipsmay be indicated in patients with knee OA43⁾. Moreover, knee OA leads to weakness of the ankle joints, plantarflexors, and dorsiflexors44⁾ and deficitsin ankle proprioception45⁾.

In this study, all patients with moderate knee OA with different grades of pain can benefitfrom a physiotherapy rehabilitation program, which was shown to be highly effective inpatients with moderate pain, although this effect might be reduced in patients with severepain. Hence, the effects of physiotherapy treatment programs might be optimised byidentifying the grade of pain and subgroups of patients.

REFERENCES