Effects of a customized biomechanical therapy

Effects of a customized biomechanical therapy on patients with medial compartment knee osteoarthritis

Osteoarthritis (OA) is the most prevalent rheumatic disease in Western populations. Occurs symptomatically in approximately 6% of adults 30 years and older, and 11% of adults 65 years and older. It is characterized pathologically by both focal loss of articular cartilage and marginal and central new bone formation. OA of the knee, the principal large joint to be affected, results in disabling knee symptoms in an estimated 10% of people older than 55 years, a quarter of whom are severely disabled.

Knee osteoarthritis (OA) is a metabolically active, dynamic process that includes both destruction and repair mechanisms that can be triggered by mechanical insults. Cartilage from some joints may experience greater mechanical load or may be more susceptible to load-induced deformation than other joints. Therefore, the knee joint may be susceptible to OA because it is exposed to greater distraction and mechanical loads than the other joints, or knee articular cartilage may be chemically more susceptible to load-induced degeneration than cartilage at other joints.

The etiology of knee OA is multifactorial and includes both generalized constitutional factors (aging, sex, obesity, heredity) and local adverse mechanical factors (trauma, occupational and recreational usage, alignment). Osteoarthritis is twice as common in women as in men, and usually occurs bilaterally. women undergo almost twice as many knee joint replacement surgeries.

Knee OA is associated with symptoms of pain and functional disability. Physical disability arising from pain and loss of functional capacity reduces quality of life and increases the risk of further morbidity and mortality.

Current treatments aim at alleviating these symptoms by several different methods: Non-pharmacological treatments (education, exercise, lifestyle changes) and Pharmacological treatments (paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), topical treatments.

Two main types of non-surgical biomechanical interventions are available for reducing pain and improving

function in patients with knee osteoarthritis. The logic behind the first type of intervention is unloading the

diseased articular surface by means of wedge insoles foot orthoses.

Studies have shown that specially designed functional knee braces  can decrease pain and improve measures of function in patients with varus knee OA. Foot orthoses have been widely used to successfully treat a range of pathologies related to biomechanical dysfunction of the lower limb. Biomechanical interventions focusing on foot center of pressure (COP) manipulation, agility and perturbation training have been suggested for the treatment of knee OA. The therapy includes daily exercise with the device, according to an exercise program that is carried out in the patient’s own environment. This device is a foot-worn platform with two adjustable convex rubber elements attached to its base. Through adjustment of the elements, the device is capable of changing the patient’s center of pressure during walking. Through this it can shift the direction of the force vector, hence change the magnitude of external moments acting on the knee joints. In a recent study, Elbaz et al. reported that the device improved gait patterns in patients with chronic non-specific low back pain. Specifically, after 3 months of therapy, the device improved gait velocity, step length, cadence and single limb support parameters of gait.

The current study was therefore devised to examine the outcome of a cohort of medial knee OA patients who were enrolled in a custom biomechanical training program. Our aim was to evaluate Changes in WOMAC and SF-36 following 3 months of Apos Therapy in patients with knee OA:


The study group was comprised of 654 patients, 446 females (68.2%) and 208 males (31.8%), diagnosed with symptomatic bilateral medial compartment knee OA were evaluated. Mean age (mean ± sd) was 64.7±8.9 years, mean height was 162.3±9.1 cm, mean weight was 84.4±31.3 kg.

Eligibility to the study was defined as follows:1. Patients suffering from symptomatic bilateral knee OA at the medial compartment for at least six months, fulfilling the ACR (American College of Rheumatology)clinical criteria for OA of the knee (Altman et al., 1986); 2. Patients that have completed the Western Ontario and McMaster Osteoarthritis Index (WOMAC) questionnaire (Roos 1999), and SF-36 Health Survey [Kosinski 1999] at baseline and after 12 weeks of treatments.

Exclusion criteria included the following: 1. neurological and rheumatic inflammatory diseases; 2. Corticosteroid injection within 3 months of the study; 3. Earlier knee surgery excluding arthroscopy; 4. Joint replacement of the hip or knee; 5. Fractures of the lower extremity less than 1 year old.

Treatment device

A novel biomechanical device (Apos System, APOS—Medical and Sports Technologies Ltd. Herzliya, Israel) comprised of convex adjustable pods placed under hind-foot and fore-foot, allowing customized calibration of the apparatus, control of body alignment and promoting perturbation through all phases of the step-cycle.

The basis of Apos therapy treatment modality is the convex form of the biomechanical elements that generates realignment of the joint and movement under perturbation, enabling dynamic, functional and repetitive training intended to improve neuromuscular control.

It promotes high numbers of repetitive movements but in a patient’s own environment thus requiring minimal change to daily activity; and it is individually customized and calibrated for each patient based on that patient’s clinical indication, enabling optimal treatment at all times.

Study protocol

Prior to their first and second examinations, patients were instructed not to consume pain medication for at least 72 h in order to eliminate the effect of these medications of the patient’s pain levels. Anthropometric measurements were drawn from the medical file of the patients. All patients underwent completed the WOMAC questionnaire and the SF-36 health survey during their first visit to the therapy center.

Patients were reevaluated after 12 weeks of treatment. After the completion of the baseline measurements, the biomechanical device was individually calibrated to each patient by a

physiotherapist certified in the APOS treatment methodology. The principle of calibration is to bring each patient’s joint to a position that allows for diminished pain while walking. In knee OA medial compartment deformity, as was the case for all our patients, the element under the hind foot is shifted laterally from the baseline position. Biomechanical, by shifting the elements in the coronal and sagittal plain, the device can be individually calibrated to shift the trajectory of the foot’s center of pressure (COP) during gait thus altering the orientation of the ground reaction force (GRF) vector and will reduce knee adduction forces. This enables decreases pressure load from the affected area in the joint during gait (Haim 2008, 2010). This is done until the patient reports minimal pain during initial contact. The element under the forefoot is shifted medially from the baseline position until the patient reports minimal pain during mid-stance to toe-off.

Once the desired alignment is achieved, the patient should report immediate pain relief while walking. At the end of calibration each patient’s device was calibrated to a different position

depending on the extent of his or her symptoms. All patients received exercise instructions and began the therapy the day after the first visit to the therapy center.

Treatment was then initiated and continued on a daily basis for a period of 12 weeks. Patients were instructed to put on the APOS device and go about their ADL for 10 min once a day during the first week and gradually increase to 30 min once a day at the fourth week and for the rest of the treatment period. After 12 weeks of treatment, patients underwent a second WOMAC questionnaire and SF-36 Health Survey.


Baseline characteristics questionnaire results are presented in Tables. There were no reports of imbalance, tripping or other physical problems during the study period. All patients complied completely with the treatment protocol.

Compliance was verified at several points during the study. After the first week and second week of treatment all patients received a telephone call to verify compliance. In addition when they arrived at the therapy center the physiotherapist also verified the patient’s

compliance to the treatment.

After the 12 week treatment period, the WOMAC-pain and WOMAC-function subscales were significantly lower. Pain decreased by 30% (P≤0.001) and function improved by 29% (P≤0.001) (diagram). All eight categories of the SF-36 health survey significantly improved

after 12 weeks of treatment. Results are summarized in Table. A further analysis of the specific effect of the treatment on the SF- 36 overall score was carried out by conducting a sensitivity analysis for sub-groups. This was carried out in order to determine if the device was only able to improve knee OA symptoms in certain categories of patients, in this case age and gender.

Age and gender were each divided into two sub-groups, age based on the median age (66 years). No significant differences between genders were found in the WOMAC pain, stiffness and function categories or in the overall score. Nevertheless, the mean score for each of the WOMAC categories and the overall score were higher in females compared to males and the p-values for the categories were all close to the significance threshold (P ≤ 0.001).

Significant differences were found in the following SF-36 subcategories: Role limitation due to physical health, energy, emotional well being and general health. Males consistently reported significantly higher values compared to females in the above categories. While the subcategories of physical function, role limitation due to emotional health, social functioning and pain were not significantly different between genders, male reported higher values in all these categories .


The results of this study suggest that there was a significant improvement in pain and function in patients treated with the biomechanical device. After 12 weeks of treatment with the device, the WOMAC and SF-36 results showed that patients reported significant and clinically relevant improvements in the level of pain, function and quality of life regardless of age and gender. Bar Ziv etal. examined randomized and double blind, the effect of this device and treatment methodology on knee osteoarthritis. They report improved function and decreased pain following APOS therapy with no changes in the level of pain and function of the control group.

The data from the self-reported questionnaires revealed differences between genders in the perception of pain, function and quality of life. As described earlier by Debi R. etal (2009), females reported a significantly poorer quality of life compared to males and probably had higher levels of pain and disability compared to males. Amother study (Tsai) found that although females reported higher levels of pain intensity compared to males, the pain intensity during walking did not differ between genders.

Overall, these studies and the current study suggest that females may experience worse symptoms of knee OA compared to males. This discrepancy highlights the importance of a comprehensive evaluation of a patient with knee OA using a variety of assessment tools, especially objective functional parameters that are able to reveal gender and age differences. It would be logical to include reported level of pain and function (WOMAC) measured in analysis test as these are objective functional tools that were able to find gender and age difference in knee OA in this study.

Knee pain is the most common health symptom in women 65 years and older and is the second most common symptom in women aged 45 to 64 years. Moreover, the prevalence of osteoarthritis in women and its associated disability will likely increase with increasing longevity.

Medical and surgical treatments for knee osteoarthritis are often limited.

Rehabilitation strategies that include alteration of shoe-wear, exercise prescription, activity modification and prescription of assistive devices such as APOS device ,may be the most critical and effective treatments.

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