By Dr Chris Milne, Sports Physician
What is it?
It occurs when the patella moves out of its usual groove in front of the knee.
What causes it?
It is caused by a variety of factors including muscle imbalance, a small or high riding patella, a shallow groove for it to track in, plus excess joint mobility and flat feet.
Symptoms – what you notice
- Pain – usually along the inner border of the patella as the muscle attachments are torn away from the bone. The pain may be very severe.
- Deformity – the patella may appear as a lump on the outside of the knee. It usually pops back into its usual groove when you straighten your knee.
- Instability – you may lack confidence in the knee, and feel it is about to give way.
- Swelling – this usually comes on virtually immediately and is related to bleeding into the knee joint.
- Effusion – usually there is a tense swelling in the knee that will last for a week or two after the injury.
- Tenderness – usually down the inner border of the patella, related to tearing of muscle attachments as above.
- A positive apprehension sign – this occurs when the doctor tries to push your patella towards the outside of your knee.
- There may be associated flat feet, or generalised hypermobility of many joints in the body.
- First aid – try to push the knee out straight, as this will often be enough for the patella to clunk back into its proper place. Apply an ice pack.
- Whether or not your patella is back in place, you need to go to an A & M Clinic to get the knee immobilised in a brace in full extension (out straight). Leave the brace on for 6 weeks.
- You should take painkillers or anti-inflammatory tablets regularly for the first few days after injury.
- If the blood in the joint is causing lots of pain, this can be sucked out of the joint by a doctor.
Perform quadriceps exercises to strengthen the muscles in front of the thigh.
- If you have flat feet, orthotics can help correct the faulty alignment in your legs.
In severe cases of recurrent patellar instability, surgery to stabilise the patella may be required.
Signs – what the doctor finds
X-rays can show an associated fracture of the inner border of the patella. A ‘skyline’ view is most useful for this. X-rays can also show a small or high riding patella, plus a shallow groove for the patella to track in. MRI scans are rarely needed but may show bone bruising, which is an additional clue in tricky cases; patellar instability is often quite subtle and may be overlooked by less experienced doctors. CT scans are usually only ordered if surgical stabilisation is being considered.
Average recovery time is 4-6 weeks, but recurrences are common.
Step 1 Get the knee out straight and the patella back in position. Ice packs, pain relief.
Step 2 Immobilise the knee in a brace for six weeks.
Step 3 Perform quadriceps exercises every day.
Step 4 Physiotherapy supervised exercises when you come out of the brace.
Step 5 Cycling and swimming.
Step 6 Restart gentle running and progress to stop-start then multidirectional activity.
Step 7 Team training and skill sessions.
Step 8 Resume playing, half game at first.