Kaleidoscope

It's a Girl thing
Part TWO ...

Also see: Part ONE

Over recent years it has become clear that female sports performers are more susceptible to certain injuries than their male counterparts.

In part 1 we discussed stress fractures. In part 2 we'll consider two common knee conditions.

The first is pain at the front of the knee, which is caused by a kneecap problem. The second is injury to the anterior cruciate ligament (ACL).

Lets take a quick look at these two conditions before we look at why female athletes are more susceptible to them and what measures can be taken to prevent them.

Philip Newton

Philip Newton is a Chartered Physiotherapist, Director of the Lilleshall Sports Injury Rehab Centre, and provides Physio cover to England players at major squash events around the world.

Figure 1

Figure 2

Figure 3

Action photos by Alex Wan

Anterior Knee Pain

Pain at the front of the knee or ''behind the knee cap'' is a common problem for many sports people and can be very debilitating. This condition has a number of names including ''Patello-femoral Pain Syndrome'' & "Runners Knee". The problem occurs between the patella (kneecap) and the femur (thigh bone). Under normal circumstances the kneecap presses against the lower portion of the thigh bone when the knee is in a bent position.

During running or any step, squat or landing & jumping activity, the kneecap moves up and down or ''tracks'' against the thigh bone and in so doing, acts as a fulcrum, which provides a mechanical advantage for the front thigh muscles (the quadriceps). High forces are produced between the kneecap and thigh bone during such activities (see figure 1).

This can amount to body weight magnified several times due to the velocities and leverages that are in play across the knee. If the normal tracking of the kneecap is altered, the result can be a localisation of these large forces onto a small area of the kneecap. This causes inflammation and pain.

So what can cause the kneecap to track abnormally? Well there are a number of anatomical and physical factors that can do this. One that is gender specific is the relative strength of the outer hip muscles, which are generally weaker in females.

These muscles support the thigh and counterbalance the weight of the whole body when weight is taken on one leg e.g. when walking & running. It may at first thought seem strange that a problem of muscle weakness at the hip can cause a problem at the knee.

This is how it works - the muscles concerned are known as the hip abductors and are situated on the upper & outer portion of the buttock (figure 2).

These muscles work every time the supporting foot comes into contact with the

ground. They prevent the pelvis from rocking excessively sideways & they also work to stabilise the thigh. If these hip abductor muscles are too weak then the knee will drop too far inwards when running, stepping & landing quickly on one foot (figure 3).

This may result in a mal tracking of the kneecap and subsequent pain. The relative weakness of this muscle group in women may be due to their wide pelvic dimensions. This places the muscles at a mechanical disadvantage as compared to hip abductor muscles that work across a relatively narrower pelvic width - as is the case in the male pelvis.

Anterior Cruciate
Ligament Injury

The Anterior Cruciate Ligament (ACL) is situated centrally within the knee and is vital to the stability of the joint (see figure 4). It is frequently injured during sport and the injuring movement can often be quite innocuous. A common way of tearing the ACL is for the sports person to be decelerating quickly or performing a quick checking movement. Upon impact with the floor, the knee twists excessively and the ACL is suddenly exposed to a massive amount of stress, which causes it to snap. For most individuals the consequence is a knee that is recurrently painful & swollen & gives way during sport or even during simple everyday activities. Such cases usually require reconstructive surgery & lengthy rehabilitation if a return to sport is to be a possibility.

So why do proportionately more females succumb to ACL tears than their sporting male counterparts? A couple of reasons have been suggested. One is based on the hypothesis that males tend to have better developed patterns of movement than females.

The suggested reasons for this are social & cultural. As an example, boys traditionally spend more time running & jumping around than girls, thereby establishing athletic patterns of movement at an earlier age.

The second reason relates to the relative weakness of the hip abductor muscles (outer buttock) that we discussed earlier. Weakness of these muscles affects how the knee is lined up when body weight is taken through it.

Insufficient strength and control of these hip muscles result in the knee collapsing inwards upon sudden foot impact with the ground. This is most likely to happen when weight is taken quickly through a semi bent knee e.g. landing from a jump or checking quickly (see figure 4).

Excessive inward rotation of the knee should be countered by the action of the outer buttock muscles. If they fail to do this, then the knee may twist so far that the ACL stretches and then ruptures.

Injury Prevention

Helping to prevent these two types of injuries involves first identifying the presence and magnitude of hip muscle weakness and then following a suitable exercise programme.

There are three simple tests that can be done to check out the strength and control of the hip abductor (outer buttock) muscles to see if their weakness could be a pre-disposing factor to injury. Two simply involve movements of the leg against gravity. The third is a single leg step movement.

Tests

The hip abductor muscles should have sufficient strength and control to raise the weight of the leg through the full available range of hip motion. Testing the strength of the muscles against gravity can check this. The first two tests involve lying on to one side with the shoulders, back and hips flat against a wall. The use of a wall ensures that the trunk remains stable throughout the test movement and that the leg remains in line with the trunk.

Test One
Bend the bottom leg for stability and keep the top leg straight with the heel in contact with the wall. Perform the test by getting an assistant to lift the top leg to the maximum position of upward movement; making sure that the leg is in line with the trunk (heel in contact with the wall). The person being tested then attempts to keep the leg in this fully elevated position as the helper removes their support. If the hip muscles are up to full strength, the leg should remain stationary and not drop (figure 5).

Test Two
Bend both knees and keep the heels and backside in contact with the wall. Perform the test by getting an assistant to lift the top leg to the maximum position of upwards movement, making sure that the feet stay together. The person being tested then attempts to keep the leg in this fully elevated position as the helper removes their support. If the hip muscles are up to full strength, the leg should not drop (figure 6).

Test Three
Stand on the leg to be tested upon a small step (approx mid shin height). Perform the test by lowering your body weight slowly and smoothly. Compare both legs. The knee of the working leg should stay in line with the supporting foot. If the outer buttock muscles (the hip abductors) are weak then the knee will drop excessively inwards, thereby placing a twisting force through the knee (figure 7).

The test movements that have just been described can be used as exercises to improve any identified weakness of the outer buttock muscles.

To be effective, the movements should be performed slowly with emphasis given to the weakest part of the movement. Regular practice of these exercises will establish a basic level of strength and control. From this base, a progression to more dynamic exercise can be made. Examples of such exercises are squat and lunge movements.

Once good hip strength has been established & this has then been followed up with a programme if step & squat conditioning exercises, the final functional progression should be made.

This involves practicing jumping, landing & cutting manoeuvres, whilst ensuring that good knee alignment is maintained.

Philip Newton

Also by Philip:
Ice With Your Bath?

A shock to the System

Also see: Part ONE