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Tuesday, June 6, 2023

Relationship between Hip Osteoarthritis (OA) and Volume Changes in Deep Muscles of the Hip

Brent Brookbush

Brent Brookbush


Research Review: Relationship between Hip Osteoarthritis (OA) and Volume Changes in Deep Muscles of the Hip

By Stefanie DiCarrado DPT, PT, NASM CPT & CES

Edited by Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Grimaldi, A, Richardson, C, Stanton, W., Durbridge, G, Donnelly, W. and Hides, J. (2009) The association between degenerative hip joint pathology and size of the gluteus medius, gluteus minimus and piriformis muscles. (2009). Manual Therapy 14. 605-610. - FULL ARTICLE

Note the difference in size of the right vs left Gluteus Medius in this coronal MRI view (white arrows)

Why is this relevant?:

Hip osteoarthritis (OA) results in femoral head and acetabular cartilage degeneration and bony changes that cause hip pain in weight bearing situations. Therapeutic exercise has varying outcomes which may be due to a lack of recognition of specific muscle impairments. Identifying specific muscle imbalances surrounding the hip in those with OA allows for a more targeted rehab program with the potential for better outcomes and long term resolution of symptoms. Most importantly, it may allow for a preventative corrective exercise program to restore proper muscle balance which may prevent joint dyskinesis and excessive wear an joint surfaces.

Study Summary

Study DesignControlled Descriptive Study
Level of EvidenceIIa: Evidence from at least 1 controlled study without randomization
Subject Demographics
  • Age (mean):
    • Mild OA: 46.5 + 9.5
    • Advanced OA: 57.7 + 6.7
    • Control: 51.8 + 9.7

  • Gender:
    • Mild OA: 3 males, 3 females
    • Advanced OA: 3 males, 3 females
    • Control: 6 males, 6 females

  • Characteristics: 12 subjects with unilateral hip joint pathology; 12 age & sex matched controls (within 5 years)
    • Mild OA: Weight: 80.4 + 15.1; Height: 171.3 + 9.7
    • Advanced OA: Weight: 78.3 + 8.5; Height: 172.0 +7.4
    • Control: Weight: 73.5 + 13.3; Height: 18.2 + 10.2

  • Inclusion Criteria: medical diagnosis with Xray/MRI showing either mild or advanced OA (as determined by an experienced radiologist)
  • Exclusion Criteria: systemic disease affecting the neuromuscular system, congenital/adolescent hip disease, history of trauma to the hip (including surgery), any inflammatory joint disease, tumors, lower limb injury or low back pain within previous 2 years, unilateral sport participation, use of ambulation assistive device, inability to receive an MRI.  Control group subjects excluded if any history of hip pain.
Outcome Measures
  • Cross section areas (CSA) of the gluteus medius (Gmed), gluteus minimus (Gmin), & piriformis (PF)
  • Calculated muscle volumes (software calculated, checked with 1 by hand calculation for validity): single slice volume = CSA x slice width; total volume = sum of all slice volumes
  • Side to side muscle volume differences within each group
    • Control Group: No significant asymmetries; Gmin commonly larger on left side
    • Mild OA: No significant asymmetries
    • Advanced OA
      • Gmed & PF significantly smaller on pathological side
      • Gmin smaller on pathological side (not statistically significant)
        • 5 subjects avg 21.5% smaller
        • 1 subject 48% larger

  • Muscle volume differences between each group
    • Mild OA vs Controls: Gmed significantly larger on pathological side
    • No other significant findings

  • No significant correlation between age, height, weight, activity, function, pain and muscle volumes
ConclusionsAsymmetries can exist in both mild and advanced hip OA.  Proper assessment of movement dysfunction and muscle imbalances along with consideration of the stage of the pathology may result in more specific rehabilitation and preventative strategies, and better long term outcomes.
Conclusions of the ResearchersIn advanced, unilateral hip OA, deep hip musculature (Gmed, Gmin, PF) decrease in size.  The Gmed, however, hypertrophies in early stages possibly due to a changes in weight bearing patterns.  Clinical assessment must consider the stage of pathology along with changes in the abductor synergy to correctly identify impairments and created more targeted rehabilitation and preventative programs.

MRI image of Gluteus Medius (orange), Gluteus Minimus (blue), and Piriformis (purple)

Review & Commentary:

This study uses data from, and builds off of, a previous study investigating changes in the TLF and Gluteus Maximus with hip OA . Researchers implemented a strong methodology with unilateral mild and advanced pathology for intra- subject comparison as well as comparison to controls. A skilled radiologist performed all MRI imaging with careful attention to leg stabilization during that process. Researchers noted age, height, weight, pain, function, and activity subjective measures but found no correlations. A longitudinal study would provide information pertaining to muscle volume changes prior to and ongoing after a diagnosis of OA and offer insight into the cause and effect relationship.

The limitations of the study are explained in the previous review Relationship between Hip Osteoarthritis & Gluteus Maximus Atrophy . Additionally, the authors disclosed the importance of future research to include concurrent EMG data to investigate a relationship between muscle volume and muscle activity.

Why is this study important?

This study demonstrated a clear relationship in muscle volumes and stages of OA pathology and filled a gap in the literature pertaining to this pathology. At the time of publication, conflicting research findings existed on changes in hip musculature in individuals with OA. EMG studies varied on their findings of Gmed  activity in OA (Long et al., 1993, Angielczyk and Bronarski, 1982, Sims et al 2002) as did Dynamometer strength assessments (Murray and Sepic, 1968; Teshima, 1994; Jandric 1997; Arokoski et al. 2002; Sims et al., 2002).

How does it affect practice?

The clinical significance of these findings is twofold. 1. The need for careful subjective and objective assessment to identify current movement dysfunctions and asymmetries for prevention / treatment of pathology. 2. The consideration of the stage of OA pathology and the affects on muscle deterioration and impaired joint mobility.

How does it relate to Brookbush Institute Content?

Individuals with mild OA tend to demonstrate hip adduction during SL stance according to Watelain et al (2001) but this study found temporary hypertrophy in the Gmed  at this stage of pathology. The TFL was also found to be larger on the pathological side . This overactivity in the TFL (along with other hip flexors) is noted in the predictive models of Lumbo Pelvic Hip Complex Dysfunction (LPHCD), Sacroiliac Joint Dysfunction (SIJD) , and Lower Leg Dysfunction (LLD)  with the Gmed  long and under-active. In this scenario, the increased adduction moment may lead to overactivity in the synergistically dominant TFL  with the Gmed  desperately trying to regain its prime mover status. The result? Hypertrophy in both muscles.

Individuals with advanced OA; however, demonstrate less adduction but more frontal plane trunk movement (Krebs et al 1998). Interestingly enough, the TFL  remained hypertophied while the Gmed Gmin , and PF  decreased in size. These change, specifically in TFL  and Gmed , call to attention the involvement of the Lateral Subsystem (LS) which is a major contributor to optimal alignment and control of the hip, pelvis, sacroiliac joint (SIJ) and the lumbar spine. Failure of the LS in single limb stance (ie during gait) can result in increased frontal plane trunk movement, a Trendelenberg Gait (dropping of one side of the pelvis -relative adduction of the femur), and joint dysfunction. The most relevant joint dysfunction within the context of this study is a superior glide of the femur in the acetabulum resulting in excessive weight bearing on that part of the bone. It would have been interesting had the researchers measured the volume of the quadratus lumborum (QL) given its propensity to become overactive along with the TFL  in those with LPHCD.

As discussed in the previous article by Grimaldi et al (2009) :

"The model employed by the Brookbush Institute addresses obstructive dysfunction first followed by asymmetries (which are often one in the same). The hip, as part of the lower extremity, is subjected to ground reaction forces and alterations in mechanics of the entire lower extremity. With that being said, LPHCD, SIJD , as well as LLD  may have an impact on hip mechanics, and should be considered when constructing an intervention for hip OA."

The following videos detail exercises to address an underactive LS .

Side Stepping Gluteus Medius Reactive Integration Activation (featuring yours truly)

Hardest Quadruped Progression Ever Challenge

Side Plank

Side Step and Step up with Shoulder Series for Lateral Subsystem Integration


Arokoski MH, Arokoski JPA, Haara M, Kankaanpaa M, Vesterinen M, Niemitukia LH, et al. Hip muscle strength and muscle cross sectional area in men with and without hip osteoarthritis. Journal of Rheumatology 2002;29:2185–95.

Krebs DE, Robbins CE, Lavine L, Mann RW. Hip biomechanics during gait. Journal of Orthopedic and Sports Physical Therapy 1998;28(1):51–9.

Long W, Dorr L, Healy B, Perry J. Functional recovery of noncemented total hip arthroplasty. Clinical Orthopaedics and Related Research 1993;288:73–7.

Angielczyk A, Bronarski J. Electromyographic analysis of the gluteus medius muscle in osteoarthritis of the hip. Chirurgia Narzadow Ruchu I Ortopedica Polska 1982;47:201–4.

Sims K, Richardson CA, Brauer SG. Investigation of hip abductor activation in subjects with clinical unilateral osteoarthritis. Annals of the Rheumatic Diseases 2002;61:687–92.

Murray MP, Sepic SB. Maximum isometric torque of hip abductor and adductor muscle. Physical Therapy 1968;48:1327–35.

Teshima K. Hip abduction force in osteoarthritis of the hip. Acta Medica Nagasa- kiensia 1994;39(3):21–30.

Jandric S. Muscle parameters in coxarthrosis. Medicinski Pregled 1997;50 (7–8):301–4.

Watelain E, Dujardin F, Babier F, Dubois D, Allard P. Pelvic and lower limb compensatory actions of subjects in an early stage of hip osteoarthritis. Archives of Physical Medicine and Rehabilitation 2001;82:1705–11.

© 2014 Brent Brookbush

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