Total Hip Replacement – Is it time yet?

Guidelines from Dr Patrick Weinrauch, Orthopaedic Surgeon. Includes podcast, infographic & podcast notes. Making the decision to undergo Total Hip Replacement (Total Hip Arthroplasty) is something that patients with hip osteoarthritis (OA) may agonise over – understandably so. Although this is generally a remarkably successful procedure with the potential to substantially improve function and quality of life, it is a big operation with substantial inherent risks and costs. I regularly see patients with hip OA who come to see me with a very specific question in mind – ‘Is it time yet? Is it time to get my hip replaced?’ There are many considerations that determine when ‘the right time’ might be for each individual. In this blog, we have been fortunate to receive some words of wisdom from Dr Patrick Weinrauch, Orthopaedic Surgeon, who generously shared his time and insights during an interview at Brisbane Hip Clinic, in Queensland, Australia. This information will be useful to guide your response when you next see a patient with advanced hip OA.

Listen to the interview here:

About Associate Professor Patrick Weinrauch :

Associate Professor Patrick Weinrauch is an Orthopaedic Surgeon, founder of Brisbane Hip Clinic in Queensland, Australia. The name of his clinic says it all. He focuses exclusively on the management of hip joint disorders, with a high level of experience and expertise in a full range of surgical procedures for the hip, including hip joint arthroscopy, hip joint preservation surgery, hip resurfacing and hip replacement procedures. Dr Weinrauch is a Fellow of the Royal Australasian College of Surgeons and a Fellow of the Australian Orthopaedic Association, and not only has a busy clinical practice but contributes to education programs for other surgeons and health professionals and to scientific research in this field. Dr Weinrauch has published over 50 peer-reviewed scientific papers and is the Deputy Editor for the International Journal of Advanced Joint Reconstruction. He is currently appointed as an Associate Professor at the Griffith University School of Medicine and has been awarded a Doctorate of Philosophy and Master of Engineering for his research relating to the surgical management of adult hip joint disorders. We are very grateful to Patrick for sharing his valuable time and wisdom.

Podcast Notes

The focus of our discussion was on hip osteoarthritis, a condition suffered by many all around the world. Hip Osteoarthritis is often managed very successfully for a long time with non-surgical care such as that supplied by physiotherapists, but for some, there comes a time when their symptoms and function begin to deteriorate despite their best efforts to look after their hip. Physiotherapists and general practitioners caring for these patients often get asked then, ‘Is it time yet? Is it time for surgery?’

Here, Dr Weinrauch discusses what factors he uses to guide his decision-making process around eligibility for hip replacement surgery

Key Points:

• The decision is very personal one, influenced strongly by how it is affecting the individual’s quality of life
• There is a considerable mismatch between changes on imaging and symptoms, some experiencing only mild symptoms with good function despite advanced
osteoarthritis and cartilage loss while others with more focal damage joint may experience quite severe symptoms.

Patient Interview includes:

  • Extensive clinical history
  • Pain – nature, location, severity
  • Function – What can’t you do? What have you had to give up? What would you like to achieve that you can’t because of your hip? If your hip was completely painfree, with no restriction from your hip, how would that change the quality of your life? How would it affect your sporting and recreational pursuits and your family life?

Key criteria for eligibility:

  • Severity that is impacting on function
  • Persistent pain over a longer duration of time
  • Not adequately responsive to non-surgical therapies
  • Good trial of non-operative therapies appropriate for their condition
  • Established wear on imaging modalities

Adequate previous trial of non-surgical management would typically include:

  • Education on hip care and conditioning
  • An exercise program for hip specific conditioning
  • Injectable therapies
  • Oral pharmaceuticals
  • Clear indications of patient commitment and compliance to a non-surgical management approach as an initial management strategy

Non-surgical management for osteoarthritic hips works! But there may be limitations with very advanced disease or particular presentations. It must be an appropriate, coordinated program with adequate commitment from patient.

Length of time to persist with non-surgical therapies depends on presentation.

There are two main presentations with hip osteoarthritis:

1. Slowly progressive

  • Mild symptoms for many years
  • Not particularly intrusive on function initially
  • Small modifications in activities over time – “creeps up”
  • Use oral medications and therapies intermittently
  • Slowly progressive until start to have more meaningful impact on function and quality of life
  • A longer trial of non-surgical intervention is appropriate, as they may just be having a flare which will settle again with good management

2. Rapidly progressive

  • Subclinical or non-symptomatic advanced osteoarthritis – not aware of having had an underlying hip problem
  • At some point develop very severe symptoms, very quickly
  • Often a trigger (increase/change activity, slip/fall, heavy impact e.g. missed bottom step), but not always
  • In retrospect may recall having some hip stiffness &/or an occasional ‘groin strain
  • This group would still have a trial of non-surgical care, but if problems persist, are likely to go to surgery more quickly

Pain location and behaviour associated with hip osteoarthritis

  • Most common location is mid-inguinal groin region
  • Worse with impact and deep hip flexion
  • Labral tears & focal/early chondral lesions more commonly present with localised mid-inguinal or c-sign pain
  • Features of advancing osteoarthritis
    • Patient begins to experience referred pain to anterior thigh and knee and also anterolateral shin pain is very common, occasionally in the buttock
    • Rest pain that is waking the patient. Note, be aware that gluteal tendinopathy may also commonly be associated with night pain, but the region of pain is over the greater trochanter, rather than the mid-inguinal/groin region.

Is hip replacement only recommended for older individuals?

This space has changed considerably

  • Prosthetic materials have become more refined
  • Bearing surfaces have become much more durable, with high wear-resistance
    Therefore, hip replacement has become a more viable option for younger people with severe persistent symptoms and advanced early hip osteoarthritis, after a good trial of non-surgical therapies. This is still a consideration however, for longer life expectancy and therefore greater chances of failure over life span.



Imaging Features: 

Radiographic changes (XRay)

  • Joint space narrowing
  • Subchondral sclerosis
  • Osteophyte formation
  • Geode formation (subchondral bone cysts)
    • Geodes appear on the acetabular side first
    • Presence of geodes in the femoral head indicates later stage pathology & reduced likelihood of a good outcome with non-surgical management

Magnetic Resonance Imaging

  • Early pathology
    • evident first on the acetabular side, in most people
    • anterior-superior acetabular rim most common initial region of change
  • As pathology advances
    • acetabular pathology progresses to encompass a larger area
    • then changes develop on the femoral side
  • Features that may influence potential effectiveness of joint preserving treatments:
    • Degree of hyaline cartilage wear will have a major influence
    • Labral pathology relatively less influence on outcome
  • DEGEMRIC scans
    • Not useful in advanced pathology with cartilage loss
    • Most useful in earlier stages of pathology to determine the quality of the cartilage, where thickness of the cartilage is relatively normal
    • Provides better ability to grade degree of cartilage change than standard MRI, where this can be very difficult
    • Not necessary if the patient is a candidate for hip arthroscopy, as arthroscopy provides an opportunity for direct visualisation and palpation of the cartilage surfaces to assess the degree of chondral pathology


That it’s for Part 1 of this interview series. If you are not signed up to the mailing list, sign up today to ensure you don’t miss the rest of this great series where we’ll be talking about non-surgical options for management of hip OA and a video interview that explores the different prostheses, surgical approaches and their indications. Don’t forget to explore the site which contains a wealth of clinically applicable information on all things hip.

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Intraarticular pathology – relevance to hip pain and joint health – Part 2

In Part 2 of this blog on intraarticular pathology, we explore the relevance of ligamentum teres tears, and effusion-synovitis.In Part 1, we discussed the relevance of labral tears, chondral pathology and bone marrow lesions with respect to hip pain and joint health. If you haven’t read Part 1 yet, you might like to go there first and then return to continue reading.

3. Ligamentum Teres Tear

The ligamentum teres (LT) contains both nociceptive and proprioceptive nerve endings, with a stable innervation pattern that persists with ageing (Haversath et al 2013). The relationship between LT pathology and nociception remains unclear with limited and variable reports of prevalence in symptomatic and asymptomatic populations. A recent systematic review and meta-analysis concluded however, that LT pathology was more common in those with hip pain (Heerey et al 2018).

Ligamentum teres tear is more likely to be present in athletes and particularly athletes whose joints are challenged by large ranges of motion (Mayes et al 2016) or the presence of morphological variations such as FAI, acetabular dysplasia or capsular laxity (Martin et al 2019). Presence of LT tear has been associated with persistent hip pain in those with labral tears, such that in one study, those with LT and labral tear were 16.5 times more likely to fail non-surgical treatment and progress to a surgical intervention that those with labral tear alone (Kaya et al 2013).

For patients presenting to clinic with joint-related pain who:

  • have pain +/- a feeling of instability in sumo-style squats/deep plie, or rotational tasks
  • are slower to respond to standard joint care
  • are/have been athletic
  • and/or have morphological variants (FAI, Acetabular Dysplasia, Capsular laxity),
    be suspicious of LT pathology.

You may need to provide more specific exercise therapy to optimise joint support in positions that challenge the LT.

Infographic_Lig Teres

With regard to the potential impact of LT pathology on joint health – from a joint stability standpoint, loss of integrity of the LT will reduce joint stability particularly in deep flexion/external rotation, end range rotation and distraction. LT pathology may be associated with microinstability, particularly in those with other morphological risk factors, with potential predisposition to early joint deterioration. LT pathology is also frequently associated with signs of inflammation of the synovium that surrounds the ligament, clearly visualised at the time of arthroscopy (Figure) and there is often accompanying inflammatory change in the adjacent pulvinar fat pad. We’ll discuss the role of inflammation in degenerative joint disease in the following section.

Synovitis of the Ligamentum Teres & Pulvinar Fat Pad

Figure: Synovitis of the Ligamentum Teres & Pulvinar Fat Pad as viewed arthroscopically. Image courtesy of Dr Patrick Weinrauch, Brisbane Hip Clinic, Brisbane, Australia.

Learn more about the ligamentum teres, pathology and implications for management in my online learning course: Anterior Hip & Groin Pain. Specific load management and therapeutic exercise strategies are covered in the practical workshop of the same name.

4. Joint Effusion-Synovitis

Effusion of the hip joint is much harder to clinically appreciate than that of other peripheral joints, due to the depth of this joint and the fact that it is encapsulated by layers of muscular structures. And yet effusion and synovitis have been associated with pain and implicated in the pathogenesis and progression of osteoarthritis (Eymard et al 2017, Hunter et al 2013, Sokolove & Lepus 2013).

The joint capsule and its synovial lining are richly innervated and a potential source of nociception (Haversath et al 2013). The synovial lining of the LT, as we have discussed, will also be a possible contributor to hip joint nociception. Less commonly considered is the possible role of highly vascularised and innervated intra-articular fat pads in hip pain and joint health. Jayasekera and colleagues (2014) described a fat pad at the anterior head-neck junction, that may become hypertrophied and inflamed secondary to repetitive femoroacetabular impingement in those with cam morphology. They hypothesised that for some patients with FAI, their pain was primarily related to this traumatised fat pad and not their labral pathology. They demonstrated that, even though the groups had no difference in cam size, if the impingement viewed arthroscopically appeared to be primarily of the fat pad rather than of the bony cam, surgical excision of the fat pad without a femoral osteoplasty returned results equal to that of cam excision.



There is also another important fat pad within the medial hip joint, the pulvinar fat pad, intimately associated with the LT and its synovium. Arthroscopists commonly note visual inflammation of this fat pad in association with synovitis of the LT. Eymard and colleagues (2017) suggest that intra-articular fat pads and their adjacent synovium should be considered unique functional units. Intra-articular fat pads of the knee and hip are composed of smaller fat cells (adipocytes) with an inflammatory phenotype characterised by a higher expression and secretion of inflammatory factors than subcutaneous fat. These intra-articular fat pads may upregulate their expression of inflammatory mediators in response to excessive mechanical loads, subsequently stimulating an inflammatory response in the synovium. The functional interaction between intra-articular adipose and synovial tissue may be a mechanism underlying OA related synovitis, with potential impacts on pain and joint health. Synovitis can drive chondral degradation and osteophyte formation and is considered to play a critical role in the pathogenesis and progression of osteoarthritis (Wang et al 2018).

What this means for healthcare practitioners is that we must be mindful of the possible presence of effusion and synovitis in those with hip joint related pain, the implications for nociception and joint health, and the potentially vital role of load management in the long term care of your patient’s hip.

Further detailed information about effective management of intraarticular hip pain is available within my video lecture series within the online learning course, Anterior Hip & Groin Pain.

In the last 2 blogs, a number of possible sources of nociception for those with intra-articular hip pain have been highlighted. All of these structures play an important role in maintaining joint homeostasis and health, although sources of nociception and mechanical and inflammatory drivers of pain and pathology will vary between individuals. Optimal outcomes may be best achieved by considering an individual’s joint status and morphological, functional and inflammatory drivers, within a biopsychosocial framework.


Atukorala, I, Kwoh, CK., Guermazi, A., et al. (2016). Synovitis in knee osteoarthritis: A precursor of disease? Annals of Rheumatic Diseases, 75, pp.390e5.
Botser, I., Martin, D., Stout, C. and Domb, B. (2011). Tears of the Ligamentum Teres. The American Journal of Sports Medicine, 39(1_suppl), pp.117-125.
Eymard, F., Pigenet, A., Citadelle, D., et al. (2017). Knee and hip intra-articular adipose tissues (IAATs) compared with autologous subcutaneous adipose tissue: a specific phenotype for a central player in osteoarthritis. Annals of the Rheumatic Diseases, 76(6), pp.1142-1148.
Haversath, M., Hanke, J., Landgraeber, S., et al. (2013). The distribution of nociceptive innervation in the painful hip. The Bone & Joint Journal, 95-B(6), pp.770-776.
Heerey, J., Kemp, J., Mosler, A., et al. (2018). What is the prevalence of imaging-defined intra-articular hip pathologies in people with and without pain? A systematic review and meta-analysis. British Journal of Sports Medicine, 52(9), pp.581-593.
Hunter, D., Guermazi, A., Roemer, F., Zhang, Y. and Neogi, T. (2013). Structural correlates of pain in joints with osteoarthritis. Osteoarthritis and Cartilage, 21(9), pp.1170-1178.
Jayasekera, N., Aprato, A. and Villar, R. (2014). Fat Pad Entrapment at the Hip: A New Diagnosis. PLoS ONE, 9(2), p.e83503.
Kaya, M., Kano, M., Sugi, A., et al. (2013). Factors contributing to the failure of conservative treatment for acetabular labrum tears. European Orthopaedics and Traumatology, 5(3), pp.261-265.
Martin, R., McDonough, C., Enseki, K., et al. (2019). Clinical relevance of the ligamentum teres: a literature review. International Journal of Sports Physical Therapy, 14(3), pp.459-467.
Mayes, S., Ferris, A., Smith, P., et al. (2016). Atraumatic tears of the ligamentum teres are more frequent in professional ballet dancers than a sporting population. Skeletal Radiology, 45(7), pp.959-967.
Mayes, S., Ferris, A., Smith, P. and Cook, J. (2018). Hip Joint effusion-synovitis is associated with hip pain and sports/recreation function in female professional ballet dancers. Clinical Journal of Sport Medicine, [23 Mar 2018].
Roemer FW, Hunter DJ, Winterstein A, et al. (2011). Hip Osteoarthritis MRI Scoring System (HOAMS): reliability and associations with radiographic and clinical findings. Osteoarthritis Cartilage, 19, pp.946–962.
Sokolove, J. and Lepus, C. (2013). Role of inflammation in the pathogenesis of osteoarthritis: latest findings and interpretations. Therapeutic Advances in Musculoskeletal Disease, 5(2), pp.77-94.
Wang, X., Hunter, D., Jin, X. and Ding, C. (2018). The importance of synovial inflammation in osteoarthritis: current evidence from imaging assessments and clinical trials. Osteoarthritis and Cartilage, 26(2), pp.165-174.

Intraarticular Pathology Blog_Part 1

Intraarticular pathology – relevance to hip pain and joint health – Part 1

With ever-increasing resolution of imaging modalities, pathology within the hip joint is easier to identify and locate.
There is however, a well-accepted mismatch between pathology and pain.

So, is all pathology irrelevant?
How do we sort out what might be meaningfully associated with pain and relevant to future joint health?

Some pathologic features are common in both symptomatic and painfree populations, while others occur more frequently in those with hip pain. The other consideration is whether structural change may have an impact on joint loading and longer-term joint health. If so, preventative education and exercise strategies may be warranted.

In the next 2 blogs we will explore 4 key pathological changes that are regularly identified in imaging and discuss their possible relevance for pain and joint health.

1. Labral Tear
2. Chondral & Bone Changes
3. Ligamentum Teres Tear
4. Joint Effusion-Synovitis

In today’s blog, we will start with the first two topics, labral tears and chondral and bone changes.

1. Labral Tear

The acetabular labrum does contain nerve fibres for nociception and for proprioception (Alzaharani et al, 2014, Haversath et al 2013), meaning that damage to this structure may contribute to hip joint related pain and also to joint protection. However, a recent systematic review and meta-analysis of the prevalence of labral pathology, revealed that while 62% of those assessed with hip pain had labral tears present on imaging, 54% of those without hip pain also had labral tears (Heerey et al 2018). Therefore, while the labrum may be a source of nociception, presence of labral pathology may be irrelevant to the pain presentation of an individual who presents to your clinic with positive imaging findings.

Infographic_Hip Pain & Health_Labral

Labral dysfunction is likely to have wider implications beyond pain. The labrum, despite only absorbing 1-2% of weightbearing loads in a hip with normal bony coverage (Henak et al 2011), has some very important functions in joint stability and chondral protection. The labrum deepens the socket and seals the joint, creating an important suction effect with negative intra-articular pressure. This vacuum increases stability and traps fluid between the head of the femur and the acetabulum to assist with cushioning impact loads (Bsat et al 2016). Injury and surgical debridement will result in a loss of the normal fluid seal, reduction of the efficiency of the vacuum, impacts on synovial flow, increased compression of cartilage due to loss of interstitial fluid and higher loads on the capsule. Debridement of the labrum has a significantly greater effect on reducing these joint protection mechanisms than the tear itself, and there is an absence of high-quality evidence for isolated labral debridement (Philippon et al 2014, Nepple et al 2014). Labral reconstruction does at least partially restore these mechanisms and yet, technical difficulty is much higher, availability is not widespread, indications are not clear, and outcomes have again not been well established.

An initial trial of non-surgical load management and exercise strategies with a well-informed physiotherapist is highly recommended for hip pain in the context of an isolated labral tear, prior to consideration of any surgical intervention. Where surgery is warranted, reconstruction would appear to be a superior alternative, when available. A risk-benefit analysis should be discussed with the patient considering a surgical intervention. In particular, a patient must understand that labral debridement does not ‘fix’ their hip.

Further detail on this topic is explored in the online learning course: Anterior Hip & Groin Pain, including discussion of load management and exercise strategies for pain associated with intra-articular hip pathology.

2. Chondral & Bone Changes

While there is a much higher prevalence of cartilage defects on imaging in those with hip pain compared with asymptomatic individuals (64% vs 12%) (Heerey et al 2018), cartilage is aneural and therefore not a source of nociception. The relationship between chondral damage and pain is most likely mediated by associated changes in other nociceptive structures such as the adjacent subchondral bone and the capsule with its highly innervated synovial lining.

Bone marrow lesions are much more likely to occur in those with painful hips, and subchondral bone is certainly innervated and may be a source of nociception. Bone marrow lesions are identified on MRI as regions of high signal uptake and therefore higher water content associated with increased bone turnover and increased angiogenesis secondary to bone remodelling processes (Shabestari et al 2016). Subchondral bone changes are usually most evident in regions of cartilage deterioration but may occur prior to the visualisation of cartilage change on imaging. For this reason, it has been suggested that subchondral bone pathology may lead to cartilage degeneration due to alteration of biomechanical force distribution or via release of biomediators that influence cartilage health (Barr et al 2015). Disturbance in the normal homeostasis of subchondral bone results in increased bone turnover, volume and change in stiffness with reduced shock absorbing capacity. If the subchondral bone becomes relatively stiffer, the adjacent cartilage will be forced to absorb more shock, potentially inducing degenerative change in the chondral surface that is unable to adequately attenuate these higher loads (Barr et al 2015).

Infographic_Hip Pain & Health_Chondral &

It is interesting to speculate that ability of the chondral surfaces to absorb load may also influence subchondral bone health. For example, labral pathology and associated impairment of the fluid seal of the central compartment is known to increase cartilage consolidation during loading. If the cartilage, which may still appear normal on imaging, is unable to absorb these increased loads, they will be transmitted to the subchondral bone. Failed bone adaptation may result in redistribution of the loads back to the chondral surface, potentiating the degenerative process. Wherever the process begins, there is evidently an intimate relationship between subchondral bone and the adjacent cartilage with respect to osteochondral load sharing, degenerative change and pain.

As cartilage is avascular, it is reliant on diffusion from subchondral bone vessels and from the synovial fluid, for its nutrition. Interference with either of these sources of nutrition may have adverse effects on chondral health. It has been shown that the primary source of chondral nutrition is from the synovial fluid (Wang et al 2018). If this fluid however contains high levels of inflammatory exudates from the synovium, these may adversely influence cartilage health (discussed in the upcoming blog – Part 2, section 4). Conversely, synovial inflammation (and nociception) may be induced by chondral debris and release of soluble cartilage matrix macromolecules into the synovial fluid, secondary to chondral damage (Atukorala et al 2016).

Learn more about morphological, movement and muscle factors that influence hip joint chondral health and strategies to minimise adverse effects, in my online learning course and practical workshop: Anterior Hip & Groin Pain.

In summary then, while the labrum is capable of nociceptive signalling, labral pathology is almost as common in those with asymptomatic hips, so the presence of a labral tear on imaging cannot be presumed to be responsible for hip pain. However, a loss of integrity in the labrum does have implications for long term joint health. Surgical debridement does not ‘fix the labrum’ and restore its function, in fact, it may further reduce its joint protective functions. Closely consider your advice around when/if surgical intervention is required for the painful hip with labral pathology. Chondral pathology and bone marrow lesions are more common in those with hip pain, with health of these tissues and the surrounding synovium intimately related.

In our next blog, we will discuss the relationship between ligamentum teres tear, effusion-synovitis, hip pain and joint health.

In the meantime, keep those hips healthy!

Alzaharani, A., Bali, K., Gudena, R., et al. (2014). The innervation of the human acetabular labrum and hip joint: an anatomic study. BMC Musculoskeletal Disorders, 15(1).
Atukorala, I, Kwoh, CK., Guermazi, A., et al. (2016). Synovitis in knee osteoarthritis: A precursor of disease? Annals of Rheumatic Diseases, 75, pp.390e5.
Barr, A., Campbell, T., Hopkinson, D., et al. (2015). A systematic review of the relationship between subchondral bone features, pain and structural pathology in peripheral joint osteoarthritis. Arthritis Research & Therapy, 17:228.
Bsat et al (2016) The acetabular labrum. The Bone & Joint Journal, 98-B(6):730-735.
Haversath, M., Hanke, J., Landgraeber, S., et al. (2013). The distribution of nociceptive innervation in the painful hip. The Bone & Joint Journal, 95-B(6), pp.770-776.
Heerey, J., Kemp, J., Mosler, A., et al. (2018). What is the prevalence of imaging-defined intra-articular hip pathologies in people with and without pain? A systematic review and meta-analysis. British Journal of Sports Medicine, 52(9), pp.581-593.
Henak CR, Ellis BJ, Harris MD, et al. (2011). Role of the acetabular labrum in load support across the hip joint. Journal of Biomechanics, 44, pp.2201–2206.
Nepple, J., Philippon, M., Campbell, K., et al. (2014). The hip fluid seal—Part II: The effect of an acetabular labral tear, repair, resection, and reconstruction on hip stability to distraction. Knee Surgery, Sports Traumatology, Arthroscopy, 22(4), pp.730-736.
Philippon, M., Nepple, J., Campbell, K., et al. (2014). The hip fluid seal—Part I: the effect of an acetabular labral tear, repair, resection, and reconstruction on hip fluid pressurization. Knee Surgery, Sports Traumatology, Arthroscopy, 22(4), pp.722-729.
Sokolove, J. and Lepus, C. (2013). Role of inflammation in the pathogenesis of osteoarthritis: latest findings and interpretations. Therapeutic Advances in Musculoskeletal Disease, 5(2), pp.77-94.
Shabestari, M., Vik, J., Reseland, J. and Eriksen, E. (2016). Bone marrow lesions in hip osteoarthritis are characterized by increased bone turnover and enhanced angiogenesis. Osteoarthritis and Cartilage, 24(10), pp.1745-1752.
Wang, X., Hunter, D., Jin, X. and Ding, C. (2018). The importance of synovial inflammation in osteoarthritis: current evidence from imaging assessments and clinical trials. Osteoarthritis and Cartilage, 26(2), pp.165-174.