What glute med really does The most significant anatomical and functional study to date conducted on the gluteus medius muscle was undertaken by Gottschalk et al in 1989(1). From their anatomical dissection studies, they suggested that the gluteus medius attaches to the outer edge of the iliac crest (top of the hip), starting at the anterior superior iliac spine (ASIS) and extending all the way to the posterior superior iliac spine (PSIS). The gluteus medius attaches to the top centimetre of the iliac crest but not to the blade of the ilium. It runs downwards in a fan shape and attaches to the antero-superior (upper front) aspect of the greater trochanter (outside of the femur), and not to the lateral aspect of the trochanter, as is sometimes incorrectly outlined in anatomy textbooks. This is important to note, as the attachment allows the tendon to contribute to anterior hip stability when the hip is in an extended positio. The muscle is divided into three equal components: anterior, middle and posterior. The fibres of the posterior portion run almost parallel with the neck of the femur, while the middle and anterior parts run vertically from the iliac crest to the antero-superior aspect of the greater trochanter. Each of the three parts of gluteus medius has its own nerve supply running from the superior gluteal nerve, suggesting that the muscle actions of the three heads are independent of each other.
Gottschalk et al reported their EMG study findings that gluteus medius is not all that active in isolated abduction of the hip. This finding may well surprise you, as it is contrary to what has been taught for years in anatomy and biomechanics lectures and textbooks. They observed that the tensor fascia lata (TFL) is significantly active in isolated hip abduction. They went on to suggest that the three heads of the gluteus medius have a phasic muscle action during stance phase of gait. The posterior directed fibres are more active at heel strike, and then the muscle becomes progressively recruited from posterior to anterior as movement occurs from early stance to late stance of gait. In other words, the front portion of the muscle (which is anatomically similar to the TFL) is most active at full stance and single-leg support phase, while the rear fibres fire strongly at initial heel strike. Gottschalk et al suggested that the main role of the gluteus medius is to compress the head of the femur into the acetabulum (hip socket) during locomotion and to assist in stabilising the pelvis on the femur in single leg stance. They then put forward the notion that each of the three distinct heads of the muscle performs a unique role in locomotion: The posterior fibres contract at early stance phase to lock the ball into the hip socket. This idea is supported by the observation that the posterior fibres have an almost parallel fibre alignment with the neck of the femur. The posterior fibres therefore essentially perform a stabilising or compressing function for the hip joint.
The middle/anterior fibres, which run in a vertical direction, help to initiate hip abduction, which is then completed by the TFL. These fibres work synergistically with TFL in stabilising the pelvis on the femur, to prevent the other side dropping (or Trendelenburg). The researchers point out that the TFL has the more important role in stabilising the pelvis on the supporting hip; the gluteus medius simply assists this action, analogous to how the supraspinatus in the shoulder assists the more powerful deltoid in shoulder abduction. The anterior fibres allow the femur to internally rotate in relation to the hip joint at mid-to-end stance phase. This is essential for pelvic rotation, so that the opposite side leg can swing forward during gait. The anterior fibres perform this role with TFL. So Gottschalk et al postulated that the primary functions of the gluteus medius are: l to stabilise the hip l to act as hip rotators l to approximate the head of the femur into the acetabulum, in effect creating a very tight and stable hip joint during gait.
This prevents the ball and socket joint from rattling around during walking and running, similar to how the rotator cuff muscles in the shoulder work to produce a tight and stable glenohumeral joint during arm elevation. How to assess glute med function 1. The single-leg squat (see Figure 2, above left) The main purpose of the single-leg squat is functionally to evaluate the dynamic quality of single-leg support as part of a kinetic chain from the foot to the trunk. It is always wrong to ignore a poor single-leg squat, as this movement shows you what will happen with the support leg during running. Technique: l Begin the movement by flexing at the hip and continue bending the knee and ankle until your thigh is parallel to the ground. l Keep hands in front of the body. l Keep trunk as upright as possible, preferably neck above toes, avoiding excessive lumbar and thoracic curvature. l Heel must stay in contact with the ground at all times.
There are a few musculoskeletal structures that contribute to poor single-leg squatting, and weak gluteus medius activity is just one factor. Table 1 (see opposite left) highlights some of these musculoskeletal issues. If a client presents with a poor single-leg squat, the therapist needs to address suspected limitations on the spot and then re-test. If the test cannot be improved because of a true weakness or limitation, the therapist will then be able to determine a plan for managing the problem, followed by a further re-test at a later date to assess the effectiveness of nd can no longer produce enough tension to cause the femur to lift and rotate.
To date, the clam test is probably the best test to assess isolated function of the posterior fibres of the gluteus medius. It assesses the muscle’s ability to slightly externally rotate and abduct the non-weight-bearing hip. It does not, however, assess the ability of the muscle to contract and approximate the hip joint to create a stable ball-and-socket joint. We will have to wait for the researchers to come up with a clinical test that assesses the hip closure role of gluteus medius.