The incidence of hip osteoarthritis (OA) is rising in western countries due to an ageing population and the epidemic of obesity. Patients with hip OA tend to complain of hip pain and stiffness which affect alignment and mobility of the whole body and typically result in general musculoskeletal pain and disability. Clinical guidelines recommend a combination of exercise therapy, weight loss and education, adjusted to the individuals needs, to be tried out before arthroplasty eventually is offered. However, to obtain a satisfactory long-term outcome is a challenge as patients may not be motivated to comply with a training program including functional strength and mobility training, if not guided by a therapist. Basic Body Awareness Therapy (BBAT) may be an alternative training modality with a better potential for lasting effects. It is a low-impact movement therapy focusing on alignment of the body and quality of movements, implemented in daily life activities. In the BBAT learning process by doing, reflecting on and transferring body awareness into daily life movements, the investigators hypothesize that the patients will obtain self-efficacy and mastering, of importance for continued training on their own. This hypothesis will be examined in the present randomized controlled trial, comparing Patient Education combined with BBAT and Patient Education alone. The investigators will, accordingly, examine the supplementary effects of BBAT for patients with hip OA. They will also explore the importance of movement quality as observed by physiotherapist using Body Awareness Rating Scale, and how it relates to how patients perceive their movement performance. In the study the investigators will particularly address long-term effects of the intervention by comparing survival of the native hip in the two groups included in the study. Data from the study will be included in a national database of patients with non-surgical treatment of hip and knee OA (NOAR), giving rise to comparison of different movement therapies.

INTRODUCTION Musculoskeletal disorders are reported to be the second largest contributor to years lived with disability worldwide, and osteoarthritis (OA) of the hips and knees among the most prevalent(1). The diagnosis of hip OA should be based on radiographic findings and symptomatic evidence (2), and a prevalence of 5.8% was reported in Norway (3). OA increases with age, every person over 60 years showing signs of osteoarthritis in at least one joint (3).

The dominant factors in OA pathogenesis is loss of articular cartilage accompanied by joint deformation, bone sclerosis, capsule shrinkage, muscle atrophy and varying degrees of synovitis (4). Physical activity is restricted by pain, and patients tend to become increasingly unfit with diminished muscle strength. Intra-articular changes are accompanied by compensatory adjustment in body posture and muscular tension, including a decrease of lumbar lordosis and thoracic kyphosis and asymmetry of the pelvis and the trunk (5). Symptoms and compensational movement adjustments have consequences for patients' daily movement and functioning, social life and self-confidence (6). A substantial increase of primary hip insertions over the last 20 years is shown in Norway by data from the Norwegian Arthroplasty Register (7). The 2014 Annual Report shows 8.099 primary hip prosthesis, and 1284 revisions, arthroplasty being more frequent in women than men (8). The risk for revisions has decreased over the years due to less aseptic loosening of prosthetic components (9), but infection is still a challenge (10).

The impact of being overweight or obese Being overweight or obese is increasingly recognized to be an important risk factor for OA in weight bearing joints (11,12). The evidence of association between obesity and development of hip OA is, however, conflicting (3,13,14). Reduction of body fat for overweight or obese people is still recommended in order to reduce both mechanical and biochemical stressors that contribute to joint degeneration (15-17).

Recommendations for non-surgical management of hip OA. There is insufficient high-quality evidence regarding non-pharmacological and nonsurgical interventions of hip OA (18-21), but clinical guidelines are rather similar in their recommendations (19,21,22).The European League Against Rheumatism (EULAR) recommends a broad range of topics like patient education, lifestyle changes, exercise modalities, weight loss, assistive technologies and adaptations, footwear and work modification, along with a biopsychosocial approach to assessment and treatment and an individualized treatment plan (21).

Patient education (PE) Empowerment of the patients by information and counseling is an important element of an up-to-date conservative treatment plan. PE was developed in Sweden by Klässbo et al. (23) aiming to empower the patients, called Better Management of Patients with Osteoarthritis (BOA www.boaregistret.se). In Sweden PE is implemented all over the country, and participation is required before total hip arthroplasty is offered (Socialstyrelsen 2012). In Denmark, PE (Good Life with osteoarthritsis in Denmark, GLA:D (www.glaid.dk ) is combined with six weeks of individualized supervised neuromuscular exercise. Even better results were shown after this program regarding pain than after BOA (24). A study examining the supplementary effects of supervised exercise vs. education alone is presently carried out on patients with severe hip OA (25). A PE called ActiveA (active living with lower limb osteoarthritis) has also been tried out for patients with hip and knee OA in Oslo (26). PE based on ActiveA principles has now been established at "Lærings- og mestringssenteret", Haukeland University Hospital (HUS) for patients with hip and knee osteoarthritis from Hordaland County.

Exercise therapy in hip OA Underlying mechanisms of beneficial effects of non-surgical treatment of hip OA are scarcely understood. Irrespective of joint, there is no evidence for effect of exercise on the pathogenesis of OA (27). It is suggested that exercise works by stabilizing the surrounding musculature of the OA-affected joint. As muscle weakness disposes to osteoarthritis, exercises may halt the progression of the disease. Endurance training can enable the patient to manage weight loss, and improve general physical functioning. Beckwée et al. (28) proposed that neuromuscular, peri-articular, intra-articular, general fitness and health, and psychosocial components might explain exercise induced improvements of pain and function.The scientific evidence for recommending therapeutic exercises for hip OA has been examined in several systematic reviews and meta-analysis (18, 29-35). Strong evidence is claimed for beneficial effects of both land- and water based aerobic and strengthening exercise programs in adults with mild to moderate OA (35), but this applies mainly to short-term effects. Some RCTs were not able to show a difference in long-term change of pain between patients who received PE combined with traditional exercises or manual therapy, versus PE alone (36, 37) or sham therapy (38). Svege et al. (39) demonstrated, however, that PE and exercises combined might postpone arthroplasty.

Recommendations are made that therapeutic exercise programs for hip or knee OA should focus on strengthening of the entire lower limb and the use of non-weight bearing exercises are questioned (32). Neuromuscular training is recommended, aiming to restore neutral functional alignment of the lower extremities, by improving dynamic motor control and functional stability (24). Although physical exercise programs are primarily recommended for patients in the early phase of OA, there is presently moderate quality evidence that preoperative exercise improves function prior to and after THA (40, 41).

How can Basic Body Awareness Therapy (BBAT) have a beneficial effect in patients with hip OA?

Empowering the patient by movement awareness learning is considered important to transform dysfunctional movements into more functional movement habits (42-44). Concrete strategies are used in BBAT to improve quality of movement in daily life. Long-lasting conditions, such as hip OA, affect multiple aspects of a persons' ability to move and function. Integrated in the BBAT program are aspects from four perspectives of human movement; biomechanical, physiological, psych-socio-cultural and existential, and movement awareness is considered a prerequisite for movement quality. Basic elements in human movement such as relating to the ground and vertical axis, freeing the breathing and finding the appropriate amount of energy required for a task, are implemented in BBAT. Movements are carried out while lying, sitting, standing, walking and also in interplay with another person (45,46). Between the Basic Body Awareness Therapy sessions, the patients are encouraged to practice movements by a) implementing the training program at home, and b) implementing quality of movements into daily life situations.

BBAT is organized as a group intervention (47, 48), and the focus is on the participants' own search for more optimal balance, core stability, free breathing and awareness, addressing movement coordination of the whole body. Evaluation of the therapy progress is done continuously by the physiotherapist together with the patients.

Pilot study A pilot study of seven patients with hip OA, taking part in Patient Education (2 hours) and Basic Body Awareness Therapy (12 times 1.5 hours weekly), was undertaken in 2014. After four months, four of seven patients demonstrated clinical significant less pain during walking. At follow-up six months later, three of five patients still reported clinical significant less pain during walking (two drop-outs unrelated to hip problem). One patient reported to be unchanged and one worse, both having minimum joint space = 0. Only the patient who reported to be worse was motivated for surgery after 10 months.

Aim for the RCT study:

To examine the supplementary effect of BBAT in patients with hip OA, by comparing the effect of Patient Education alone with Patient Education and BBAT combined.

METHOD Design The randomized controlled trial will include patients with primary hip OA randomized to one of two study arms; 1) Patient Education and Basic Body Awareness Therapy, or 2) Patient Education only.

Participants Patients with verified hip OA (by x-rays and clinical symptoms) are recruited among patients who are referred from Primary Health Care to Orthopedic department at Haukeland University Hospital to participate in Patient Education at "Lærings- og mestringssenteret". Written informed consent is a prerequisite for participation.

Sample size Pain by Numeric Rating Scale (scale 0-100): The expected difference in change between the groups is 17 points on the 0-100 Numeric Rating Scale, which is considered the minimum important difference in improvement (53). Based on a previous study (54), the investigators assume a between-participant standard deviation of change of 30 points. The required sample size, with 80% power and type I error of 0.05 is 44 in each group. Allowing for a 15% drop-out, a total of 100 patients is required.

Disability by the HOOS ADL subscale (0-100): Seventy four patients are needed to detect a clinically significant change of 10 points on the HOOS ADL subscale with SD=30, power=0.80 and alpha= 0.05 (55).100 patients will accordingly be a sufficient sample size for HOOS.

Randomization and blinding: A computer-generated block randomization schedule is used to allocate participants into one of two groups after 1) given written informed consent to participate in the study, 2) having filled in questionnaires and been tested by a blinded assessor, and 3) having participated PE. A research coordinator not involved in the randomization procedure, prepares opaque envelopes with allocation to groups.

Interventions Patient Education: The overall focus of Patient Education is empowerment of the patients by increasing their knowledge of the hip OA condition and learning how to deal with it. The patients' own experiences with hip OA and active sharing in the group will be in the forefront. Basic Body awareness Therapy (BBAT): BBAT will be implemented as a group therapy (48). A group will include 5-10 patients, be led by a specialist physiotherapist qualified in BBAT, and offered once a week. Each session last for 90 minutes, and includes movement practice (70 minutes) followed by talk (20 minutes) to let the group members share movement experiences. The participants are consecutively admitted to the class, and participate in 12 sessions. In this way experienced participants will share experiences and motivate novices. BBAT will be offered as group therapy in Primary Health Care.

Analysis of RCT: Comparison of change between the randomized groups will be performed by linear regression (ANCOVA) analysis, controlling for baseline scores. Per protocol and intention-to-treat analysis will be performed.

Ethical considerations: The project is conducted in conformity with the "Declaration of Helsinki". Approval from the Regional Ethical Committee was recived in September 2015.

Inclusion Criteria:

• Women and men with primary OA according to the American College of Rheumatology Clinical Criteria, living in Bergen or within a reasonable travelling distance (judged by the patients).

Exclusion Criteria:

• Other known major physical or mental problems or disease that precludes movement training and participation in an educational program, known drug abuse, not speaking or understanding Norwegian language, pregnancy 5-9 months.

After the RCT has been completed, the plan is to enter data in a national register for patients with osteoarthritis, NOAR. The patients give their consent to this.

The data will be available from January 2021 to January 2023

All data that has relevance to NOAR will be shared

The assessment at inclusion was done before randomization, and was also blinded at follow-ups