The gluteus medius (GM) is one of three muscles that make up the gluteal group, it is a fan shaped muscle positioned on the lateral and upper aspect of the pelvis just below the iliac crest, it narrows down to the tendon and attaches on to the superolateral side of the greater trochanter of the femur. Gluteus mediums plays a vital role in locomotion and single limb weight bearing. Without the support of GM the pelvis would drop in a single limb stance, the GM contracts allowing the opposite side of the pelvis to be raised this allows the raised limb to be brought forward for the next step, if this muscle is weak or paralysed walking is awkward and difficult and running nearly impossible. The Trendelenburg sign/gait is when in a single limb stance the contralateral side of the pelvis drops due to the inability of the opposite GM to pull on the ilium raising the contralateral pelvis, (Palastanga and Soames, 2012:228,229).
A weak gluteus medius has been shown to contribute to lower limb injuries; patellofemoral pain syndrome (Cichanowski et al; 2007), iliotibial band friction syndrome, (Frederickson et al; 2000), ACL sprains and chronic ankle instability, (Hewett et al; 2006), through the influence of joint loading patterns and lower extremity control, (Ireland et al; 2003). Knee Valgus (when the knee is in a more medial position), is an obvious example of poor lower extremity control, it is a combination of hip internal rotation and adduction (Griffin et al; 2006). As GM abducts and the posterior fibres of GM externally rotate the hip strengthening of this muscle could assist in the correction of knee valgus.
Patellofemoral Pain Syndrome
Patellofemoral pain syndrome (PFPS) is one of the most commonly reported chronic knee problems associated with active individuals, (Boling and Padua; 2013:662). Biomechanical factors have shown to be key attributes in the risk of developing (PFPS) creating malalignment and altered pressures in the patellofemoral joint, these factors include decreased strength in the hip and thigh musculature and altered mechanics during dynamic activities such as running and landing, (Powers; 2010:40) in order to decrease the stress through the PFJ musculature control needs to maintained through the lower limb, if hip musculature is weak it has been shown to alter kinematics through the PFJ during dynamic movements as the knee moves into a more valgus position, (Souza and Powers; 2009:12).
The single leg squat is the most common observed screening method for knee valgus, (Atkins and Herrington; 2014:62). A valgus knee places more strain on the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL). On landing single legged eg stance phase in running, forces transmitted through the knee on initial contact could cause strain, it is also possible that the lateral meniscus could be damaged as the joint angle has decreased and extra pressure is placed on this lateral structure which is thinner than the medial menisci. Females are more prone to knee valgus due to wider pelvis therefore creating a larger Q angle, this is the angle produced by the femur and the tibia, an angle larger than 14° for men and 17° for women can produce mal tracking of the patella which can lead to pain and injury, (Ka-lam; 2010: 65).
Exercises for Gluteus Medius
The anterior and posterior fibres of gluteus medius are responsible differing roles; the anterior fibres are responsible for medial rotation with a fixed pelvis and with a fixed femur rotates the opposite side lf the pelvis forward. With a fixed pelvis the posterior fibres assist in hip external rotation. Abduction is created as gluteus medius contracts it pulls on the greater trochanter moving the femur upwards. If the lower attachment of the hip is fixed contraction of gluteus medius pulls the ilium down lowering the pelvis on that side and raising the other side, (Palastanga and Soames, 2012:228,229).
Many exercises have been prescribed to strengthen the gluteal muscles for the prevention and rehabilitation of injuries through correcting faulty movement patterns and have demonstrated success, (Tyler et al; 2006). Exercise 1 is the most common; ‘Hip Clams’ this is performed side lying with knee flexion at 90° and hip flexion at 60°, with hips facing forward and heels kept together throughout the movement the knees were abducted then returned to the starting position, (Distefano et al; 2009:534).
Excise 2; Side lying hip abduction can be performed by side lying with hips in neutral and knees in full extension, the upper leg is abducted to 30° then returned to the starting position, (Distefano et al; 2009:534).
Exercise 3; Lateral band walks, a theraband is placed around the ankles the feet are hip width apart hips and knees are maintained at 30° of flexion, starting position is feet together leading with dominant leg the participant sidesteps 130° of hip width, (Distefano et al; 2009:534).
Exercise 4; A single leg squat where the subject stands on one leg with hip and knee at 30° flexion and the subject lowers themselves into the squat using the hip knee and ankle until the middle figure of the contralateral hand touches the toe of the working leg then return to the starting position, (Distefano et al; 2009:534).
Distefano et al (2009) completed an electromyography (EMG) was performed on the gluteus medius during each of these exercises to ascertain which is the most effective, previous studies have stated that muscle activation greater than 50% – 60% (maximum voluntary isometric contraction (MVIC) is conducive for strength gains (Ayotte et al; 2007)) they concluded that gluteus medius is most effective at side lying hip abduction worth almost 16% more activation than the other exercises but all came above the 50% threshold for MVIC.
In order to find the cause of patellofemoral pain the lower limb needs to be looked at as a whole, muscle length tests and muscular imbalances need to be assessed and the Q – Angle needs to be measured along with observation during dynamic movements and a knee valgus assessment. Where a weak GM is observed careful consideration must be taken into the exercises prescribed, the side lying clam exercise is often prescribed but Otten et al (2015:249) agree with Distefano et al (2009) that it is the least effective exercise for strengthening GM, according to the literature a side lying hip abduction to 30° is the best exercise to effectively engage the muscle fibres of GM. Although this exercise is most effective it’s not functional and as a movement is not performed during sport or in daily life therefore a more dynamic single leg squat or lateral band walks would be more effective for sport and day to day activities.
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