Medial knee pain

The Medial Collateral Ligament is the ligament supporting the inside of your knee.

In the USA it is injured in 0.24 people per 1000, meaning in a city the size of Glasgow there is potentially 180 MCL injuries per year. Generally this is a sporting injury where a force pushes the knee in the way as shown here:

It can also occur with rotation or a combination of both movements. There are a number of important structures which support the inside of the knee. These are:

• Superficial MCL
• Deep MCL
• Posterior Oblique Ligament

These structures have a complex role, and complement each other in protecting the knee. The Superficial MCL has 2 functions:

1. protecting against valgus (inwards movement) stress at the knee
2. protecting against external rotation stress at the knee

It therefore acts as the main(primary) stabilising structure on the inside of the knee. This is supported by other structures, and the deep MCL provides secondary protection against valgus stress.

The deep MCL and posterior oblique ligaments provide secondary restraints to external rotation(foot turning out) stress at the knee. The same structures also act to stabilise against internal rotation (foot turning in) stress to the knee.

So that’s whats there, how do we diagnose an injury to this area?

Well, as always the history of the injury is a big clue. Nearly all injuries to the medial knee will have had a valgus stress to the knee, with or without contact. Some from a tackle, some from a fall/landing that went wrong! There will also be those with biomechanical problems whose leg position irritates the medial knee structures.

The physical examination should comprise at least the following tests:

• Valgus stress testing in extension and 20-30° of flexion
• Dial Test
• Anteromedial drawer test

These tests will allow diagnosis of the classification of the injury, and the structures involved. Valgus stress in extension with an isolated MCL injury should have only a small amount of laxity, a large amount may indicate a combined injury with cruciate involvement. The Dial test, although traditionally used to assess the opposite corner of the knee can be positive in medial knee injuries.

Where there is doubt over the diagnosis or extent of injury, stress x-rays can be used to confirm the amount of laxity and MRI can be used to determine the location and extent of the injury, which is reported to be 87% accurate(Yao et al).

Classification is based usually on a 3 stage model of progressive damage:

• Grade 1

Pain along medial knee on testing but no ligament laxity

• Grade 2

Pain on medial knee, with laxity but the ligaments still have an end feel

• Grade 3

Complete ligament tear with no identifiable end feel on testing the ligament

There may be some difficulty in determining the cause/location of an injury in a chronic problem, and given the rotatory aspect to this, as described above, can be confused with a posterolateral corner injury. Therefore, the anteromedial and posterolateral draw tests can be used to differentiate along with careful interpretation of a dial test.

So now we know a bit about the medial knee, and how to tell if it’s injured.

What to do with it?!?

Typically the first choice of treatment in an isolated MCL injury is rehabilitation. Unless there is a combination injury with other knee structures e.g. ACL or PCL or meniscus, where a different thought process is required.

The aims of most rehabilitation programs are:

• Protect the healing ligament
• Restoring muscle function around the knee
• Restoring full range of motion
• Removing swelling from the knee

There are many rehabilitation programs available, but most include the above principles, expected recovery time depends on the desired outcome of the program and the severity of the injury, though an average of 5-7 weeks has been proposed(Wijdicks et al, 2010)

There is some debate regarding the use of brace post injury, and early movement is shown to be beneficial from as soon as tolerable (La Prade, 2012). Side to side movements should be avoided until at least 3-4 weeks in a grade 2/3 injury to allow good healing to take place.

A post on knee rehabilitation will follow in the near future, so keep a look out!