Efficacy of the Generation II Unloader Knee Orthosis in improving Lysholm Knee Rating Scale Scores in Patients with Medial Compartment Osteoarthritis

Abstract

Osteoarthritis of the knee joint can result in pain and instability, thus limiting the functional abilities of those stricken. The percentage of the world's population at risk for suffering pain and limitation due to OA is increasing considerably. These people are typically greater than 50 years old and are at high risk for surgical complications. Patients who are younger than 50 years old are also not optimal surgical candidates due to the high probability that they will require multiple revisions later in life.

Conservative management of mild osteoarthritis with heel wedges and neoprene sleeves has been suggested to be effective. In moderate to severe OA with reduction of the medial tibio-femoral joint space, a valgus inducing orthosis may be the only viable option to unload the medial joint and reduce pain during ADL's.

The purpose of this study was to determine whether patients would report less pain during normal ADL's after 1 month of orthotic treament with a Generation II Medial Unloader Knee Orthosis. The subjects included 9 patients that were referred to our clinic for orthotic management of knee osteoarthritis with c/o medial knee pain, and genuvarus. The subjects were asked to complete a Lysholm Knee Scale Questionnaire at the time of casting, then again at 1 month follow- up. Although 7 out of 9 patients reported improvement in pain and functional ability following treatment, there was no significant difference in functional knee scale scores obtained following orthotic treatment compared to those reported prior to orthotic management.

Introduction and Background:

Osteoarthritis (OA) is the most common disorder affecting synovial joints, with structural changes present in approximately half of the adult population (4). Kellgren and Lawrence performed clinical and roentgenologic assessment and deduced that 80% of persons 55 years or older experienced OA. The knee is the most commonly affected weightbearing joint, and varus deformity is the most common malalignment of the knee associated with osteoarthritis (4). As "baby boomers" are presently reaching this age, we expect that a growing percentage of the American public will be faced with pain and disability due to OA. It has also been documented that this population of patients is at a much higher risk for complications during surgical procedures, therefore conservative alternatives may be a better option for many of these people (7).

Knee joint loading during walking or other routine ADL's has been shown to reach several times the loading caused by a static standing posture (1). A larger component of this reaction force is born by the medial compartment of the knee. Changes in bony alignment or loss of intrinsic soft tissue stabilizers can lead to increased asymmetry of knee joint loading patterns and cause more rapid progression of degenerative changes. For example, the presence of varus angulation results in approximation of the medial tibial plateau and medial femoral condyle which increases load on the medial compartment and accelerates breakdown of joint surfaces. Further more, the patient will often compensate by attempting to regain stability by forcefully contracting the musculature about the knee. This will also increase the compressive force across the joint. As the patient ambulates, the ground reaction force passes medial to the knee joint thus producing an adduction moment. This adduction moment combined with increased joint play due to loss of joint congruency results in high repetition, ballistic stretch of the surrounding soft tissue stabilizers. Since the bony anatomy of the knee joint does not provide any intrinsic stability, chronic lengthening of the collateral ligaments will result in gross coronal instability, and amplify the varus thrust during stance.

High tibial osteotomy has been used to reduce the varus deformity of the knee in an attempt to normalize bony alignment and reduce loading of the medial compartment. Unfortunately, patients who present with high adduction moments during gait prior to surgery have been shown to maintain that pattern or revert back to it within a few years post surgery (1). Many of these patients progress rapidly to requiring total knee replacement. Even then, a high incidence of component loosening is seen in patients who remain in varus. These unreliable surgical outcomes combined with risk of surgical complications, high cost, and time loss from normal work and activity make conservative treatment options attractive to many patients.

Orthotic treatment has been used as part of the conservative treatment for knee medial compartment osteoarthritis. Most common types or orthoses used include wedged insoles, knee sleeves, and unloading braces. Wedge insole orthoses have been shown to be effective only in early-stage OA; severe OA is not affected (7). Neoprene knee sleeves provide little or no mechanical support to the knee but may have some effect on improved stability and reduction of pain. Kirkley reports that good results have been described anecdotally however no controlled trials have been reported supporting the use of a sleeve. Unloading braces were developed to create a valgus force on the knee and reduce compression of the medial compartment during gait, which can be excessive when genuvarum due to OA is present. One such orthosis, the Generation II (G II) was designed in Canada by Generation II Orthotics Ltd. It is a polyaxial hinged brace that induces an increasing amount of valgus force to the knee as the patient moves from knee extension to flexion. The valgus force is thought to be beneficial in correcting bony alignment, and lessening the effect of the adduction moment placed on the knee in stance thereby reducing compression force in the medial knee compartment. If the medial joint space in OA patients could be enlarged using this orthosis, painful symptoms might be eliminated or decreased affording the patient improved function during ADL's.

Studies supporting Valgus bracing for OA would be useful to many members of the rehabilitation team. Physicians and surgeons can learn whether conservative options can be used instead of, or possibly in conjunction with surgery to correct bony alignment, protect prosthetic implants, improve knee stability and reduce the amplification of forces across the joint surfaces. Physical therapists may be interested in learning whether orthotic treatment can assist in reducing pain, thus allowing patients to maintain their current functional level while performing exercises to strengthen the knee stabilizers. Orthotists can benefit from research that explores not only the use of Valgus bracing for treatment of knee OA, but also the use of outcome measures to evaluate the effect that orthotic treatment has on the patients perceived level of pain and disability.

The purpose of this study is to evaluate the effectiveness of valgus bracing for medial compartment knee osteoarthritis, to assess the appropriateness of the Generation II Unloader Orthosis in patients with medial knee joint OA, and to examine the use of the Lysholm Knee Rating Scale as a functional outcome measure for support of orthotic treatment of knee osteoarthritis.

Previous Investigations

Matsuno et al. studied 20 subjects who were all >55 y/o with bilateral knee arthritis but retained at least 50% of normal tibio-femoral joint space, and could walk at least 500 meters independent of support. The side experiencing the most severe symptoms was fitted with a Generation II Medial Unloader Knee Orthosis that was worn at all times except for at night.

Clinical Assessments were performed each month following GII application. The functional objective efficacy of the orthosis was assessed utilizing the modified knee scoring system of the Japan Orthopaedic Association, which evaluates pain on walking and on climbing up and down stairs. X-rays were taken both in and out of orthosis every 2 months. Quadriceps muscle strength was assessed isokinetically using a dynamometer. A stabilometer was used to record the excursion of the patients center of gravity during 30 seconds of static standing.

The authors reported that the JOA Knee Scores significantly improved with application of the orthosis and continued to improve throughout the 12 month observation period. The femorotibial angle (genuvarum) decreased after 2 months in the orthosis and remained decreased at 12 month follow-up. The isokinetic quadriceps muscle strength with the brace on increased throughout the full range of motion. Also, decreased total movement of the center of gravity was noted in the orthosis suggesting improvement in the lateral stability of the knee (7).

Hewett, Noyes et al. studied 19 subjects with persistent chronic medial tibiofemoral compartment pain that affected sports or daily activities, arthroscopic or radiographic documentation of medial compartment arthrosis, or varus osseous alignment. Patients were fitted with a valgus inducing orthosis (Bledsoe Brace Systems) and were instructed to wear the brace for as many hours and for as many days of the week as they wished. All patients had undergone multiple operative procedures, including arthroscopies, partial or total meniscectomies, high tibial osteotomies, and anterior cruciate ligament reconstruction. Evaluation was performed before brace wear, after the initial follow-up evaluation (mean: 9 weeks), and after the final follow up evaluation (mean: 46 weeks). Patients completed a Cincinnati Knee Rating System questionnaire, and visual analog scale. They were asked how many minutes they could walk without significant pain, how painful their knee was after 30 and 60 minutes of mall shopping, and whether none, some, or significant pain relief was provided by only the brace, by only the medication, or by both the brace and the medication. Patients were also asked to rate the overall condition of their knee on a 1 to 10 scale with 1 indicating the poorest knee and 10 indicating a normal knee. At the two follow-up evaluations, patients were asked to provide and average of hours per day and days per week that the brace had been worn. X-rays were repeated at follow-up, and 9 patients underwent gait analysis testing.

According to the authors, 78% of the patients reported severe pain with ADL's prior to brace wear, compared to only 39% at the first follow-up and 31% at the final follow-up. Pain analogue scale scores decreased significantly between the pre-orthosis and both follow up evaluations. Reported walking tolerance increased from 51 minutes pre-orthosis to 138 minutes at 9 week follow up. The patients reported average walking tolerance of 107 minutes after 1 year of wearing the valgus inducing orthosis. Gait evaluation showed no change in the mean value for the knee adduction moment in stance. At pre-brace evaluation, the mean patient's self perception of knee score was 3.4 points out of 10. At the first follow-up evaluation, the mean score had improved to 5.4, and it remained improved at 4.7 at second follow-up (2).

Kirkley et al. randomized 119 patients into 3 groups to compare the effectiveness of valgus bracing (GII) to patients treated with a neoprene sleeve and a control group, which received no orthosis. Two disease specific, health related, quality of life measures and two functional scores were used at the baseline and all follow-up evaluations. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and McMaster-Toronto Arthritis Patient Preference Disability Questionnaire (MACTAR) were used to assess the patients perceived functional limitations while a six minute walking test and 30 second stair climbing test were used as functional measures.

The authors reported that patients who underwent valgus bracing showed significantly improved WOMAC scores compared to the group that wore a neoprene sleeve, who in turn improved significantly more than the control group. No significant difference could be detected between the unloader brace group and the neoprene sleeve group, or between the sleeve group and the controls. Distance walked and the number of stairs climbed during functional testing were not statistically different among the three groups at 6 month assessment however pain scores in the valgus braced group were significantly less than those for the neoprene sleeve and control groups following both tests(4).

Lindenfeld et al. examined whether a brace designed to unload varus degenerative knees actually alters medial compartment load by decreasing the knee adduction moment during gait. Eleven patients who had undergone arthroscopic debridement and other associated arthroscopic procedures for persistent medial knee pain during ambulation, but continued to have pain post surgically were used for the study. These patients were fitted with a valgus knee brace ( Big Sky Medical, Bozeman, MI) and underwent gait analysis before and after a minimum of 4 weeks wearing the brace. They also completed questionnaires and were interviewed for the assessment of symptoms, sports activities, and functional limitations according to the Cincinnati Knee Rating System. Results were compared to a group of controls without a brace, with no knee injury, that were matched for walking speed and performed identical tests.

Investigators reported that pain symptoms decreased significantly with brace wear. The pain scores recorded from analog pain scale decreased 48% in the brace group, activity level achieved without pain symptoms increased 69%, and function with activities of daily living score of the Cincinnati Knee Rating System increased 79%. Nine of 11 patients had a decrease in the adduction moment of the involve knee when wearing the brace, with the moment decreasing by as much as 32% (5).

Methods:

All patients (n=11) who were referred to our clinic from 1/1/2001 and 6/30/2001 for orthotic treatment secondary to knee osteoarthritis who presented with varus angulation of the knee (varus >0 degrees), and complained of medial knee pain were asked to participate in the study. Patients were excluded from the study if they reported a past medical history that includes: knee surgery, hip surgery, cardiac or respiratory problems, recent lower extremity fractures, loss of sensation in the legs or feet, or open wounds within the trim lines of the orthosis, or if they had ever worn a knee orthosis. No patients were excluded because of age, race, or gender. One patient was excluded from the study due to lack of follow-up, and one additional subject was excluded due to inconsistent responses on his questionnaire compared with his functional level. All patients who were not excluded (appendix A) and agreed to participate were asked to sign a consent form (appendix B). Participants were asked to complete a Lysholm Knee Scale Questionnaire (appendix C). The Lysholm Knee rating scale is reported to have an intrapersonal and interpersonal coefficient of variation of 3%, and 4% respectively. Test-retest reliability level was excellent with a calculated correlation coefficient of .97 (6). This scale is especially appropriate for self-evaluation of function in the typical OA patient in that unlike most other knee function questionnaires, it assesses normal ADL's rather than sports specific activity. The scale is easy to administer and score. All patients were fitted with a Generation II Medial Unloader Knee Orthosis as per manufacturers specifications (Generation II Orthotics Ltd., Canada). The patients were instructed to wear their orthosis whenever they were active. At 1 month follow-up, the patients were asked about any problems that they may have experienced with the orthosis and whether they had complied with the prescribed wearing schedule. They were also asked to complete another Lysholm Knee Scale Questionnaire.

Knee Scale Scores were calculated as recommended by Lysholm. Pre-orthosis and post-orthosis scores were compared statistically using a paired T-test design with significance level of .05, and were used to prove or disprove the research hypothesis that valgus bracing is effective in reducing the Lysholm Knee Rating Scale Scores in patients with pain and functional limitation due to medial compartment osteoarthritis.

Results:

Initial Lysholm Knee Scale scores ranged from 26% to 64% with a mean score of 45.1%. Treatment time preceding follow-up ranged varied due to patient non-compliance with scheduled follow-up appointments. Mean follow-up time was 10.9 weeks with a range from 4 weeks to 27 weeks. Post-treatment Lysholm Knee Scale scores ranged from 16% to 93% with a mean score of 63% (Table 1).

Data was compared using a 2 tailed paired t-test. The t-test indicated that the Lysholm Scale scores at follow-up were not statistically different from those obtained prior to orthotic treatment at a significance level of 0.05.

Conclusion:

The results of this study suggest that although 7 out of 9 subjects reported improvement in pain and functional ability after treatment, there was no significant difference in functional knee scale scores obtained following orthotic treatment compared to those reported prior to orthotic management. The subject sample size utilized in this study was small due to time constraints. Treatment time was not well controlled and varied significantly between subjects. Additional studies with larger sample sizes, better regulation of treatment time, specific patient populations, and the use of other manufacturers orthotic devices for valgus knee bracing are needed to explore the efficacy of this treatment.

APPENDIX A

Name:_______________________ AGE:______________________

Have you ever had any of the following?

                                                                                  Yes No Don't Know

1. Knee Surgery                                             ___ ___ ___

2. Hip Surgery                                                ___ ___ ___

3. Cardiac or Respiratory Problems         ___ ___ ___

4. Recent Fractures                                      ___ ___ ___

5. Loss of Sensation in your legs              ___ ___ ___

6. Open wounds on your legs or feet        ___ ___ ___

Have you ever worn a knee brace? If so what type?

Do you know of any reason that it may be harmful for you to wear a knee brace as prescribed by your physician at this time? If yes, please explain:

_____________________                    _____________________
       Participant                                                            Orthotist

Appendix B

References

1. Andriacchi T. Dynamics of Knee Malalignment. Orthopedic Clinics of North America 1994; 25: 395-403.

2. Hewett, T.E.; Noyes, F.R.; Barber-Westin S.D.; Heckmann, T.P. Decrease in knee joint pain and increase in function in patients with medial compartment arthrosis: a prospective analysis of valgus bracing. Orthopedics 1998; 21: 131-138.

3. Horlick S; Loomer R. Valgus Knee Bracing for Medial Gonarthrosis. Clin J Sport Med1993; 3: 251-255.

4. Kirkley, M.D., et al. The Effect of Bracing on Varus Gonarthrosis. Journal of Bone and Joint Surgery 1999; 81-A: 539-548.

5. Lindenfeld, Hewett, T.E.; Andriacchi T. Joint Loading with Valgus Bracing in Patients with Varus Gonarthrosis. Clinical Orthopedics and Related Research 1997; 344: 290-297.

6. Lysholm. Rating Systems in the Evaluation of Knee Ligament Injuries. Am J Sports Med. 1982; 10: 150-155.

7. Matsuno, H; Tsuji, H. Generation II Knee Bracing for Severe Medial Compartment Osteoarthritis of the Knee. Arch. Phys. Med. And Rehab.1997; 78: 745-749.

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