PT on the Net Research

Weak Gluteus Medius and the Implications on Knee Rehab


It was anything but a smooth transition from the Manly Rugby League side back to Rugby Union for Craig Innes.

During a game in March, after only a few weeks back with the Auckland Blues rugby team, Innes twisted his knee awkwardly at the bottom of a ruck. The result was a torn cartilage (meniscus) in the left knee that would require immediate surgery to remove the injured fragment.

This is regarded as a reasonably common injury in sports like rugby, with a quick recovery once the torn fragment is removed with an arthroscope. Most players are running within two weeks following the surgery and are generally back to full fitness after four to six weeks. However, in Innes’ case, the knee continued to remain swollen and painful four months following the surgery and was preventing his return to the Blues.

Personal Trainer Tony Townley saw the need for further assessment to outline the possible causes of this slow recovery. It was decided that a full biomechanical evaluation should be undertaken to assess the overall function of the left leg. Resistance training up to this point was severely restricted due to the constant joint irritation, although the necessity to resume full strength following this type of surgery meant that full intensity had to be resumed as soon as possible.

A muscle imbalance and lower limb assessment revealed some interesting findings.

A weight bearing test showed that Innes had a discrepancy of 15 kg more down his injured left side than the right. This test is performed by getting the client to stand on two calibrated scales (similar to bathroom scales) and measuring the difference between each side. This increased weight bearing on the left was an unusual finding, as the body will often compensate for an injury through a weight bearing joint by moving away from that side, therefore reducing the load on the affected area.

In this case, the extra load was obviously creating stress on the injured meniscus, which was irritating the joint and therefore delaying the healing rate. The next step was to identify the reason for this excessive weight shift.

The answer was to be found in a small, but very important, muscle on the outside of the left hip. The name of this muscle is gluteus medius, and when tested, the right was significantly stronger than the one on the left, resulting in an imbalance.

The action of gluteus medius when weight bearing (i.e., standing or walking ) is to support the hip and basically keep the leg straight in relation to the pelvis. If this muscle fails to contract with each step, the result is a sideways slumping motion toward that side (this is occasionally referred to as a Trendelenburg gait). This instability creates excessive weight transfer to the affected side and therefore can increase the load on the knee joint.

The answer based on these findings was to strengthen the offending weak muscle in an attempt to restore even loading on the left knee.

PHASE ONE

The exercises in Phase One were aimed at increasing the firing rate of the nerves supplying gluteus medius on the left to provide an enhanced stabilizing effect.

Wall Slides

The right hip is pressed into the wall by an isometric abduction of the left hip. Note that the left hip is held in slight lateral rotation to shorten the posterior fibres of gluteus medius. Once control is achieved in the upright position and an adequate contraction of the gluteus medius is maintained, a single knee bend can be performed. Contraction of the lower abdominals throughout these exercises helps to improve stability.

Single Knee Bends

Notice in this exercise, the Theraband is looped around the pelvis to provide a lateral pull to the right. The client is asked to perform a single knee bend while maintaining perfect lower limb alignment. The right iliac crest should remain slightly higher than the left throughout the exercise.

Single Knee Bends

Very similar to the Theraband exercise above. The wobble board creates an unstable environment, creating the need for further stabilization from the gluteus medius. After one session of these exercises to stimulate the left gluteus medius, the weight bearing discrepancy was reduced from 15kg to 5kg. The conclusion was made that the increased neural activity due to the isolated work would have the desired effect. To enhance the effect of the added stability, an isolated strengthening program was also introduced.

PHASE TWO

The knees are flexed to 90 degrees; the hips are flexed to approximately 45 degrees.

Theraband Raises

The movement of lifting the knees apart while keeping the feet together creates abduction and lateral rotation of the left hip. The movement is held at the top of the range to work into inner range.

Wobble Board Leg Press

A unilateral leg press is executed with the foot placed on a wobble board. The hip knee and second toe must be held in alignment throughout the movement.

Cable Hip Rotations

These exercises were used to isolate the lateral rotation component of posterior gluteus medius. The resistance is via an ankle strap, which is attached to a low setting on a pulley.

Side Lunge

A lunge movement is performed to the side stimulating contraction of the gluteus medius on the left. Once again correct lower limb alignment is checked along with contraction of the lower abdominal muscles. These exercises were monitored very carefully with regards to the level of irritation on the knee joint . The side lunges were added last in this phase as this would place increased strain on the knee. The isolated movements such as the cable rotations and the theraband raises were always performed at the end of the programme to reduce the chance of fatiguing the stabilisers prior to performing the more compound movement patterns.

PHASE THREE

The last phase of the conditioning involved ballistic exercises to teach the client to recruit these muscles quickly when loaded in a sport environment.

Box Side Steps -1 Box Side Steps - 2

In this exercise, the client jumps off a box toward the effected side. The stability on impact is achieved with contraction of the gluteus medius on the left. The client is instructed to achieve perfect lower limb alignment on impact, keeping the center of the patella in line with the middle of the foot and is not allowed to let the right ASIS drop below the level of the left on impact.

Side Jumps - 1 Side Jumps - 2

The client in this exercise is instructed to jump off the left foot as shown in the first image to land on the right. Once again, the movement is performed laterally to emphasize stability in the frontal plane. The next repetition would see the client jumping back across to the left. Innes showed vast improvements once he regained control of his hip stabilizers. This improved stability allowed him to proceed with resistance work to restore the strength in his quadriceps with improved alignment. The original reason for the imbalance may have been associated with Innes’ position in League. As a left sided player, he was continually moving to the left by pushing across off his right hip. The body quickly learns to favor the more active side and may have "switched off" the gluteus medius on the other side. Gluteus medius provides very important stability of the lower limb during any weight bearing activities. Once weak, it can contribute to injuries, many of which are distant from the site of the problem. When isolated and trained effectively, the results can be dramatic.