Family doctor

Overview

• The knee is the most commonly injured joint in the body
• It is a modified hinge joint and relies upon strong ligaments and muscles for its stability
• Most injuries to the knee involve either the patellofemoral joint, a ligament strain or cartilage (meniscus) tear
• Most knee injuries can be improved significantly by modified activity, and specific muscle rehabilitation exercises
• If a clear structural problem exists (e.g. unstable meniscal tear) then surgery is necessary

How do knee injuries occur?

The most important clue to making the correct diagnosis in knee injuries is the mechanism of injury. That is in which direction the joint was forced when it became injured.

Common mechanisms of injury and the structures involved include:

• Fall with impact on the front of the kneecap (patella). This injures the contact area behind the kneecap, called the patellofemoral joint.
• Being tackled from the side, with the force causing opening up of the inner side of the knee, this strains the medial collateral ligament.
• A twisting injury. This often injures the cartilage (meniscus) and a cartilage tear may result in knee locking.
• A pivoting injury where the foot is planted. This injures the anterior cruciate ligament.

Symptoms you should take note of:

Pain

The location of pain can indicate which structure is injured. For example pain in the front of the knee is often associated with patellofemerol joint injury. Pain on the inner side of the knee may be associated with a medial ligament strain.

Locking

Locking is the inability to fully extend the knee. It may be caused by a torn cartilage (meniscus) with a fragment trapped in the knee, or a torn anterior cruciate ligament.

Instability

This is a feeling that the knee is about to give way. It is usually associated with anterior cruciate ligament rupture, but there may be other causes.

Swelling

The onset of swelling in relation to a knee injury is crucial. Swelling which develops in the first hour or two after the injury is due to blood accumulating within the joint. This happens with a torn anterior cruciate ligament, a fracture within the joint, or a dislocated patella. Swelling which is not evident until the next day is associated with accumulation of joint fluid such as occurs with a cartilage tear.

Making a specific diagnosis:

Your doctor will ask you about how your knee injury occurred, and the particular symptoms mentioned above. Following this, an examination is undertaken.

Initial observation will reveal whether or not there is excess fluid on the joint, and if any scars (from previous injury or surgery) are present. Touching gently around the joint (palpitation) can help determine the site of maximum tenderness. Joint line tenderness is associated with a cartilage tear.

Testing the range of knee motion is then undertaken. Normal knee motion is from 0 to 140 degrees.

Finally, specific stresses through the knee can help assess any associated ligament tears. If there is increased excursion (laxity) on testing a particular ligament, then the ligament has either been significantly stretched or completely ruptured.

Once the above tests have been performed, the doctor should be able to make a working diagnosis - that is give a label to the problem that can be used to plan treatment.

What about x-rays and scans?

X-rays are helpful in certain situations:

• If a fracture is suspected, based on findings from the history and physical examination.
• In all cases of haemarthrosis (blood within the knee joint) because there may have been a dislocated patella. If this is suspected, skyline views looking down through the knee joint are worthwhile.
• If an orthopaedic surgeon is to be consulted, x-rays are useful to check for associated boney problems.
• In cases of persistent pain, as bone tumours can occasionally present as pain after injury.

More specialised scans e.g. MRI scans are generally ordered by specialists e.g. orthopaedic surgeons or sports physicians.

What about rehabilitation?

All knee injuries can benefit from a planned programme of exercises. Initially, the aim is to reduce knee swelling and protect injured ligaments.

Ice, compression and elevation are important in the first 48 hours after a knee injury.

Anti-inflammatory tablets may be prescribed for a few days, particularly if joint swelling is present.

If there are signs of a complete rupture of the medial ligament, a limited range of motion brace is helpful.

Once the first few days have passed, there is an emphasis on gradually restoring the full range of motion of the knee. Careful attention to maintaining function of the quadriceps muscles (at the front of the thigh) and the hamstring muscles (at the back of the thigh) is important.

Over the next couple of weeks, the aim is to have these muscles working in concert. Even though a ligament may be strained, good muscles can help in maintaining knee stability as the ligament heals. Swimming is useful at this stage.

Once the full range of knee motion has been restored, it is important to build power and endurance. Functional exercises (e.g. stair climbing) are generally of more use than expensive machines in achieving this.

As knee function improves, cycling then light jogging can commence. Once the person can jog painfree, then they can start speeding up and slowing down. If this causes no problem, they can try running around cones in a figure 8 pattern. The next step is to try cutting and turning movements. If these cause no problem, it is safe to return to team training.

Once skills have been re-established, the player can return to competition. It may be advisable to play half a game initially, and be prepared to come off the field if the knee gives any problem.

The role of surgery:

Surgery has a significant place in the management of more severe knee injuries. If there is a torn cartilage with locking of the knee, or a torn anterior cruciate ligament causing recurrent instability, then surgery is very useful.

There are only rare instances where surgery is necessary in the first few days after a knee injury. Generally these involve fractures, or complete dislocations of the knee, which are uncommon. For injuries such as a torn anterior cruciate ligament, it is best to settle the acute swelling and restore muscle function before embarking on ligament reconstruction. The pre-surgical rehabilitation is called pre-habilitation and enables better results to be achieved from surgery.

Following surgery, post-operative rehabilitation is necessary to restore optimal knee function. All this takes time, approximately five months for a torn anterior cruciate ligament. There's no point in rushing things, you want this knee to work well for the rest of your life!