Evidence Based Practice

The Association Between Degenerative Hip Joint Pathology and Size of the Gluteus Medius, Gluteus Minimus, and Piriformis Muscles

Dr A Grimaldi et al, Manual Therapy, 14 (2009) 605-610 

This study looked at the difference in size of the abductor synergy in the control group (no OA) compared 

to mild and advanced OA of the hip using MRI.

(N = 12 with pathology, N=12 control)

The hypothesis was that there would be significant asymmetry of the GMED, GMIN and PIRI muscles at the affected hip, compared with the non-affected hip, and that the GMED, GMIN and PIRI muscles would be smaller with more advanced OA.

Those with mild OA tend to increase adduction at the hip during stance, and those with advanced OA tend to reduce adduction by increasing the frontal plane of the trunk.

The study concludes that there are changed in the GMED and PIRI muscles (smaller) in those with advanced OA. However, the study also concludes that the abductor synergy does not respond uniformly with changes in pathology.  The GMED, GMIN and PIRI muscles may atrophy but the TFL and Upper glut max continue to work effectively.  it has also been found that with mild pathology, GMED may actually hypertrophy rather than atrophy.

"Assessment and rehabilitation strategies should carefully consider stage of pathology and specific changes occurring within the abductor synergy. This more specific approach may improve long term outcomes of conservative intervention in the management of OA of the hip, and may provide a direction for future prevention programmes."

Lateral Hip Pain: Mechanisms and Management (Article in InTouch magazine, APA)

Written by Dr A Grimaldi

Lateral hip pain has commonly been referred to as trochanteric bursitis.  Recent evidence shows there is more bursal distension rather than acute or chronic inflammation, secondary to the compressive forces that occur along the lateral side of the hip with glut med (or min) tendinopathy.  Compression is thought to be a key factor in the development of insertional tendinopathies .  Compression of the glut med and min tendons into the lateral and anterior aspects of the greater trochanter occurs beneath the level of the ITB; with increased tightness of the ITB, compression loading and overactivity then occurs in the superficial  lateral stability system, namely TFL, upper glut max and vastus lateralis.  Sitting in saddle chairs can promote excessive static abduction, thus tightening the above structures and causing lateral hip pain in those who are largely sedentary at work.  On rising from a chair, the hips are brought into adduction, thus compressing the lateral structures, particularly glut med and min, causing pain.  

Grimaldi reports that a study by Birnbaum et al (2004) found that in neutral adduction, there is only 4N of loading over the greater trochanter.  With only 10 degrees of adduction, this rises to 36N and rises again to 106N with 40 degrees of adduction.  Therefore stretching the lateral structures can often exacerbate the problem.

Aggravating factors such as sitting for prolonged periods, sitting cross legged, sleeping on both the affected and non-affected side and standing in the positive Trendelenberg position can all affect the length-tension relationship of the lateral structures.  Excessive lengthening of the lateral structures contributes to the increased adduction in stance and thus increases the compressive force over the greater trochanter.  The increase in adduction also biases the superficial abductors and shows poor recruitment in the deeper rotators/abductors.

Other factors can predispose an athlete to this condition.  For example, pelvic obliquity with scoliosis, leg length discrepancy, hip flexor dysfunction (think soccer players striking the ball with their leg crossing the midline) and running/walking gait abnormalities, especially on the camber of a road or uneven surface like sand.

Treatment strategies are now moving away from the ice, ultrasound and stretching regime commonly associated with bursitis.  Education has been proven to be effective with exercise decompression compliance programmes and also reassures the patient that tendon recovery will take time.  Addressing negative habits such as sitting cross legged, standing hanging on one hip or sitting with feet wide and knees together will help with pain relief in the short term and reduce the pull of the TFL on the gluteal and thoracodorsal fascia.   Avoiding low chairs or using a wedge cushion to bring the hips higher than the knees can also be effective.  

Night pain is difficult to address but trying to sleep supine with a pillow under the knees can often take the pressure off the hips.  Sidelying using a pillow to keep the affected side in neutral adduction can sometimes work.

Short term relief can be achieved by dry needling, heat, massage and trigger pointing and physiotherapists can show their patients how to perform self trigger pointing.  Long term relief can only come from addressing the poor recruitment patterns and working on the muscle dysfunctions.

Lateral stability mechanism
Deepest layer is Gluteus Minimus, which attaches to the superior joint capsule, contributing to joint stability and protection.
The intermediate layer consists of all 3 sections of Gluteus Medius, and also Piriformis.  GMED comprises of anterior, posterior and superficial segments, all with separate innervation and all with independent movement patterns.


In order to maintain the pelvis in a neutral state, the gluteals contribute 70% of the workload and TFL/UGM and the ITB contribute 30% (with VL helping out).