Manual Therapy on Activation of the Descending Pain Inhibitory System in Patients With Knee Osteoarthritis

Introduction: Knee osteoarthritis is a clinical syndrome which is characterized by pain. It has been shown to cause changes in the nervous system leading to central sensitization. There are factors involved in this disease such as sex (female) or obesity. The most recommended therapy is physical therapy, but manual therapy is needed to cause changes in central sensitization.

Methods: Experimental, prospective, parallel and longitudinal double-blind study, in which two groups are performed: group A (AP mobilizations) and group B (Mulligan's mobilizations). Different variables and questionnaires were used: pressure pain threshold, temporal summation, pain modulation, central sensitization inventory, WOMAC, Times Up \& GO, numerical rating scale, Beck, STAI, kinesiophobia, catastrophism, Barthel and mini- cognitive test

INTRODUCTION Osteoarthritis is a degenerative joint disease characterized by a decrease in joint space due to cartilage loss, subchondral sclerosis and osteophytes. Knee osteoarthritis consist in a clinical syndrome that is identified by the presence of pain and can be associated with radiological and laboratory tests Radiology was incorporated by the American College of Rheumatology as a valuable element in the classification of osteoarthritis. Considering the radiological findings and the presence of pain as sufficient criteria for diagnosis The scale used is that of Kellgren and Lawrence, which has 5 grades ranging from 0 to 4, with the greater the degree, the greater the severity marked by the successive presence of decreased interarticular space, sclerosis, cysts and joint deformities. Despite the radiological findings, 40% of the individuals do not have pain.GA is the most significant cause of pain and limitation in the elderly. The prevalence of this disease in Spain is 46% in women and 21% in men over 45 years. Women and African Americans are at greater risk of suffering from osteoarthritis of the knee. The incidence is higher with increasing age. A very important risk factor in the development and progression of this disease is obesity.

The pain of knee osteoarthritis is a multifactorial phenomenon in which structural, neurophysiological and psychosocial factors are involved. With regard to neurophysiological factors, it has been found that there are inflammatory mediators within the articular cartilage which alter afferent sensory inputs and cause plastic changes in the nervous system leading to central sensitization (CS).

Sensitization is defined as an increased response to a painful stimulus, accentuating the signal in the central nervous system, either by increasing the pain signal or by decreasing the pain inhibition signals.

On the other hand, magnetic resonance studies have shown that patients with gonarthrosis have a higher degree of vigilance and a lower capacity to disconnect pain, related to the abnormal activity of different areas of the brain such as the prefrontal areas, the cingulate cortex, the insula, the amygdala and the nucleus accumbens.

The therapies that have had more evidence are pharmacological, non-pharmacological, surgical, infiltration, physical therapies, and lifestyle changes. Because most have side effects, physical therapy is often advised.

The investigators found studies using multimodal treatments, which aim to look for synergistic effects to achieve a better outcome. But it has been shown that if these treatments do not include manual therapy they do not cause changes in central sensitization.

The hypothesis of the study is that with AP and Mulligan's mobilizations the investigators can activate the downward chain.

Primary Objective To evaluate the effectiveness of joint mobilization versus Mulligan's treatment on the activation of conditioned pain modulation, temporal summation, and generalized and local mechanical hyperalgesia Secondary objective As secondary objectives, we will evaluate the effect of accessory mobilizations versus Mulligan's treatment on disability, functionality, central awareness characteristics and psychosocial aspects.

METHODOLOGY RESEARCH DESIGN It is an experimental, prospective, parallel and longitudinal double-blind study with elderly patients with knee osteoarthritis.

PARTICIPANTS Selection of participants: elderly participants from a resident of the elderly in Comunidad de Madrid, who are informed of the procedure and asked for informed consent.

SAMPLE SIZE The sample size will be calculated by means of the "Gpower 3.0.18." computer program.

RANDOM Randomization will be done through the GraphaPad software (GraphPad Software, Inc CA 92037 USA). Patients who meet the inclusion criteria and have none of the exclusion criteria will be entered into the study and the sample will be randomized to obtain the two groups, in opaque, sealed envelopes: A and B.

MASKING The double-blind criteria are met, in which the subjects participating in the study will not know the group to which they were assigned, as well as the physiotherapist in charge of collecting the variable data.

Eligibility Criteria:
Inclusion Criteria:

* Knee pain diagnosed with osteoarthritis of the knee using the criteria of the American College of Rheumatology
* Low or no response to pain medication for osteoarthritis knee pain.

Exclusion Criteria:

* Suffer from any disorder, syndrome or disease that may cause myofascial or neuropathic pain in the lower limbs, such as lumbar radiculopathy, meralgia paresthetica or saphenous nerve entrapment.
* Infiltration with steroids or local anaesthetics during the year prior to the patient's participation in the study or during follow-up.
* History of previous lower extremity or lumbopelvic surgery.
* Ingestion of substances of abuse that may interfere with treatment.
* Contraindications to perform joint therapy mobilizations.
* Previous diagnosis of myopathy or neuropathy (lumbo-sacral plexus)
* Cognitive deficit manifested in the clinical history (Alzheimer, dementia).