Common causes of hip pain include muscle or tendon injuries, bursitis and arthritis. Magnetic resonance imaging (MRI) is commonly used in the assessment of hip pain. It provides a high-resolution image of bone ligaments, tendons, muscles and other soft tissue structures.  However, MRI findings are not always the cause of hip pain. A recent review by LaTrobe University found that changes in hip joint structure on MRI, such as labral tears and cartilage defects, can be found in asymptomatic individuals.(1) For example changes were found in those without pain and/or loss of hip function. A study by the Australian Ballet Company supports this finding when they found MRI results did not always match up with their dancers symptoms or lack there of.(2) They suggested that caution should be made when interrupting MRI results as they may not be the source of a dancer’s symptoms. There are also studies that have found hip pain in the absence of MRI findings.(3) This may explain why some people can function at a high level without pain despite having positive findings on MRI. It may also help to explain why other people continue to experience pain following surgery to repair problems that were found on MRI.  Therefore, we need to be cautious when interpreting MRI findings.

MRI can assess muscle size and quality around the hip

An emerging area of research is the measurement of the size, shape and quality of muscle on MRI. Research performed so far in this area shows us that the hip muscles change their size, shape and quality as a result of hip pain. Quality can be assessed by measuring how much fat is present within a muscle. An increase in fat percentages means that there is less contractile tissue available and therefore less capacity to generate force. This corresponds to reduced strength and function of the muscle and this is a problem because it leads to more pain and loss of function.

Have a look at the figure below which shows normal muscle tissue in the gluteal muscles (A- Gluteus Minimus, B- Gluteus Medius, C- Gluteus Maximus) on the left compared to the fatty streaks throughout the muscles on the right.

Hoffman et al. 2012 (4)
Hoffman et al. 2012 (4)
Fatty muscles? What can we do about this?

The hip is a ball and socket joint. In another ball socket joint, the shoulder, we know an increase in fat within the shoulder muscles is associated with poorer surgical outcomes. Could this also be the case for the hip joint? If so, can we identify those at risk of poor outcomes using MRI and offer them high-quality rehabilitation?

My PhD research aims to answer these questions. In a group of young football players, I will look at measurements of hip muscle size, shape and quality and determine whether these MRI measurements are associated with changes in hip joint and quality of life over a two-year period. The results of my PhD will help us understand how hip pain in younger people evolves into hip osteoarthritis later in life so we can develop better early-stage interventions.

Exercise helps hip pain

In the meantime, while we wait for these results, we know that exercise helps with a range of painful hip conditions. A targeted exercise program, such as the ones prescribed by physiotherapists, can reduce hip pain and improve function. A great example of this is the GLA:DTM program which is an exercise and education program targeted at individuals presenting with symptoms of hip and knee osteoarthritis. Research has shown that this program can reduce pain scores, increase function, improve quality of life measures and even prolong the need for hip surgery. So the best advice I can give you is don’t just sit around and wait for it to get better, get exercising!

References
  1. Heerey JJ, Kemp JL, Mosler AB, Jones DM, Pizzari T, Souza RB, et al. 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. 2018;52(9):581-93.
  2. Mayes S, Ferris A-R, Smith P, Garnham A, Cook J. Similar prevalence of acetabular labral tear in professional ballet dancers and sporting participants. Clinical Journal of Sport Medicine. 2016;26(4):307-13.
  3. Brukner P, Clarsen B, Cook J, Cools A, Crossley K, Hutchinson M, et al. Clinical Sports Medicine, Volume 1, Injuries. 5. painos. Australia: McGraw-Hill Education. 2017.
  4. Hoffmann A, Pfirrmann CWA. The hip abductors at MR imaging. European Journal of Radiology. 2012;81(12):3755-62.