Lateral knee injury: don’t get sidelined by iliotibial band syndrome

In part one of a two-art article, Pat Gilham explores the characteristics of iliotibial band syndrome, which leads to pain in the lateral region of the knee in runners and cyclists, and also outlines the risk factors for developing this injury

Iliotibial band pain syndrome (ITBPS) is a condition characterised by sharp pain affecting the outside of the knee. Originally, researchers believed that this occurred due to friction’ at the point where the iliotibial band (ITB) attaches to the outer part of the knee. However, subsequent research suggests this is unlikely because of the anatomical thickness of the ITB tissue, which prevents any sliding movements of the tissue over the bony protrusion known as Gerdy’s tubercle(see figure 1 below)⁽¹⁾. Instead, ITBPS is now thought to be generated as a result of compression to pressure-sensing fatty tissue above Gerdy’s tubercle’ on the outside of the knee ⁽¹⁾. This compression causes local inflammation, which is thought to cause symptoms that are common in athletes, particularly runners and cyclists^(1,2).

Figure 1: Anatomy of the iliotibial band (showing Gerdy’s tubercle)

The ITB is a thick longitudinal extension from the tensae fasciae latae (TFL) muscle on the outside of the hip, and has attachments to the gluteus maximus of the buttocks also. It has an average length of 88cm covering the full length of the thigh bone, and attaching onto the end of the thigh bone and beginning of the shin bone. It is a stiff structure and can only lengthen 0.2% when placed on full contraction by the TFL⁽¹⁾.

How common is ITBPS?

The incidence of ITBPS in runners is estimated to be between 5-14%, and it is the most common running injury to the outside part of the knee. It appears to be more common in men: in the ITBPS population, the prevalence of women is reported to be between 16-50%, and for men between 50-81%⁽²⁾.

What does ITBPS feel like?

ITBPS is commonly described as an aching pain on the outside of the knee, which can be sharp at times and sometimes in a pin-point location. This pain is normally aggravated by running, particularly downhill. Runners usually report symptoms presenting at a consistent distance in the run each time⁽³⁾. Commonly, alterations in distance, terrain, technique, or speed can all be triggers for ITBPS; the implication is that any changes to training routine should be introduced slowly - perhaps no more often than every two weeks.

Diagnosis

Diagnosis can be made following an assessment by a skilled clinician - for example, a physiotherapist - who will take into account your history and symptoms. Due to the clarity of the presentation of this condition, further investigations are usually unnecessary. However, magnetic resonance imaging (MRI) or ultrasound (US) scans can provide further confirmation (see figure 2)^(2,3).

Figure 2: MRI image of knee affected by ITBPS

Figure 2: Different angles of an MRI showing signs of changes to the ITB where it attaches to the knee (white arrow showing small area of increased whitening).

What is the purpose of the ITB?

The ITB is controlled by the TFL muscle. Along with the gluteus maximum, the TFL tightens the ITB, and (through it’s attachment to the outside part of the knee) helps the front thigh muscles (quadriceps) to create a straightening action of the knee⁽⁴⁾. When in weight bearing, the TFL and ITB help to steady and control the movements of the pelvis and thigh bone on the shin bone, which of course is very important when considering the impact created when running (see figure 3 below).

Figure 3: action of ITB during running

Why are runners at risk?

A runner’s biomechanics can predispose them to ITBPS. Small changes in angles can be a catalyst, particularly when considering the repetition involved in running. It is very hard to monitor technique externally without using video technology. The following variables to reduce the risk of ITBPS should be monitored when running:

*Knee bending angle when landing

Runners have an average knee bend angle of 21˚ at foot strike. However, runners become at risk of ITBPS with a knee bend angle occurring at, or slightly less than, 30˚⁽³⁾. As a result of this angle, the fatty tissue underneath Gerdy’s Tubercle is thought to be repeatedly compressed, therefore causing pain. In terms of running gait, this can be caused by over-striding or prolonging your contact time with the ground when landing^(5,6).

*Foot cross-over landing

When running on a treadmill, imagine a line going down right down the middle. Cross over landing is when your left foot strikes across this line to the right side and vice-versa (see figure 4) . This landing pattern increases the inwards angle of the knee and hip when striking the floor and is therefore thought to contribute to ITBPS⁽⁵⁾.

Figure 4: Crossover landing

*Opposite hip drop when landing (Trendelenburg gait)

When landing whilst running, imagine a line reaching from one side of your pelvis to the other, much like a belt would. If the opposite hip drops to below this line, it is thought to encourage more strain to the outer hip tissues upon landing, which is thought to contribute to ITBPS at the knee^(5,6). This can be referred to as a Trendelenburg gait (see figure 5).

Figure 5: Trendelenburg gait when running

 

A (on left) shows a normal gait). B (on right) shows a Trendelenburg gait, leading to increased loading on the weight-bearing hip soft tissue.

In the next part of this article, we will look how best to treat ITBPS with therapy and rehabilitation exercises.

References

1. Scand J Med Sci Sports, 2009. March 1-8
2. Sports Med, 2012. Nov 970-992
3. Brukner, P. in: Khan K. 2007 (3rd ed). Clinical Sports Medicine. Sydney. PA: McGraw-Hill Companies.
4. Palastanga, N. 2006 (5^th ed). Anatomy and Human Movement: structure and function. Butterworth Heinemann.
5. Br J Sports Med, 2016. Dec 1-16
6. Iliotibial Band Syndrome: What is it? www.drandyfranklynmiller.com/itbs/