By David Colvin…

• Recent Advances in Arthroscopic Surgery
• Treatment of Patellofemoral Pain

The patellofemoral joint refers to the kneecap (patella) and the groove it runs in at the front of the knee (trochlea).

The quadriceps muscles on the front of the thigh connect to the top of the patella. It is then connected to the tibia (shin bone) by the patellar tendon. The point of attachment is a bone prominence called the tibial tuberosity.

When the quadriceps muscles contract they pull on the patella and it causes the knee to straighten. The hamstring muscles at the back of the thigh bend the knee. The patella acts as a pulley, moving up and down in the groove at the front of the knee as the knee bends and straightens. Normally the patella does not move from side to side.

PROBLEMS WITH THE PATELLOFEMORAL JOINT

Problems occur when the patella does not run smoothly and centrally in its trochlear groove.

(a) Patellar dislocation

The patella can be completely displaced out of its groove. The first time this happens it usually requires a significant injury, but it can become recurrent with minimal force. Because of the shape of the human knee, it always dislocates to the outside of the knee, never the inside. Dislocations can chip the bone (patella or trochlea) and recurrent dislocation can cause arthritis.

(b) Patellar maltracking

This is less dramatic but similar in nature. It is also very common. Instead of running in the centre of the groove the patella runs over towards the outer side of the groove (patellar tilt and subluxation). This results in pain (patellofemoral pain) and premature wear (chondromalacia patellae) or if severe, patellofemoral arthritis.

It usually occurs because of the shape of the knee you are born with, but can be aggravated by such thing as flat fee, weak hip muscles or tightness of the iliotibial band on the outer thigh, or injuries.

PATELLOFEMORAL PAIN

Several factors may indicate the knee pain is coming from the kneecap (patella).

1. Pain at the front of the knee, which may go through to the back or out side
2. Associated `grating’ sensation
3. Pain worsened by going up or down stairs, on hills or inclines or uneven surfaces
4. Pain or `restless leg’s with prolonged sitting such as at a movie, on a plane or in the car
5. Pain with running, so-called `Runner’s knee’.

INVESTIGATIONS

• X-rays will show up arthritic changes if they are moderate to severe
• MRI scans are more sensitive in showing early wear on the joint surfaces or `chondromalacia’.
• The position of the kneecap in the groove is best seen on a patellofemoral CT scan, which can measure the severity of the tilt and displacement.

TREATMENT FOR PATELLOFEMORAL PAIN

Patellofemoral pain is notoriously difficult to treat and tends to grumble along for long periods. All treatments aim to reduce the severity of symptoms, but seldom result in a complete cure, especially if there is some arthritic wear already. There are three main treatment options;

1. Non-surgical treatment

This should always be tried first.

(a) Physiotherapy

The main aim of rehabilitation is to strengthen the inner quadriceps muscle (the vastus medialis obliquis or VMO) to pull the kneecap back into a central position. It requires a few physiotherapy sessions to learn some specific exercises, then they are done individually on a daily basis for at least three months. It is a significant undertaking in terms of time and self-discipline to do this, but no other treatment should be considered until the patient has tried it. Surgery is not a shot cut – indeed surgery will only succeed if this muscle group is also strengthened.

General leg exercises and fitness is also not a substitute for these specific VMO exercises, but some general low-impact strengthening such as cycling walking or swimming should be undertaken. Running is not advisable as it is high impact.

Intensive physiotherapy is not necessary, just a few sessions to learn the exercises.

The physiotherapist may also help with some stretches for the iliotibial band (ITB) and gluteal muscle strengthening.

(b) Taping and bracing

The physiotherapist can also tape the kneecap across into a better position. The taping gives us a good idea of what improvement can be achieved. If taping is useful, a removable brace can be fitted for exercise / sport / work.

(c) Weight loss

Weight loss alone will often fix the problem if the patient is substantially overweight. Equally importantly, surgery will not work if the patient remains overweight after surgery.

(d) Orthotics

Will correct flat feet, which aggravate these problems.

(e) Pain killers

Simple Panadol (six to eight tablets a day) is the safest analgaesic. It can be combined with an anti-inflammatory such as Nurofen.

(f) Cortisone injections

This is a megadose of anti-inflammatory into the knee and is good for severe flare-ups.

(g) Botox injections

To paralyse the outer thigh muscles. The role of this treatment is still being investigated.

2. Arthroscopic surgery with lateral release

Keyhole surgery can achieve two things. Firstly we can smooth off roughened areas of arthritic wear. This is called chondroplasty. It may reduce pain levels. It does not reverse the arthritic wear, and does not stop the grating or clunking sensation (which will usually be permanent).

More importantly we can release the fibrous band of tissue attached to the outer side of the patella to produce an immediate improvement in the `tilt’. This produces a permanent effect very similar to taping or bracing. The tissue we are cutting is not structural and does not weaken the knee.

At arthroscopy we also remove any bone fragments (called loose bodies) or torn cartilages.

3. Tibial tubercle transfer

Often referred to as a patellofemoral reconstruction (or realignment), or Fulkerson procedure. As `reconstruction’ implies, it is major surgery for severe pain that has failed to respond to all other treatment. It is also a good operation for knee cap dislocation. When we do this procedure it is always combined with arthroscopy and lateral release at the same time.

The operation involves cutting the bone where the patellar tendon attaches to the tibia, and shifting this bone across to the inner side and re-attaching it with screws. This is the most effective way of repositioning the kneecap.