What is patellar instability?
Your patella (knee cap) is a small triangular bone that sits in a groove at the bottom end of your thigh bone (femer). As you bend and straighten your knee, your patella slides up and down in this groove, controlled by ligaments and muscles.
If your patella doesn’t stay fully in the groove, either during movement or when you are resting, this is called patellar instability.
What are the main symptoms?
If you have patellar instability it’s likely that you will have some pain around the front of your knee and possibly swelling. Your knee might also feel weak or loose and you might feel like you don’t trust it fully to support you.
The symptoms range from minor laxity, where the knee cap moves slightly out of the groove causing a distinctive clunking sensation (patellar maltracking), to dislocation of your knee cap altogether. Dislocation can be momentary, where the patella relocates itself or it may dislocate and stay out until it is manipulated back into position.
Unfortunately, the more times your knee cap dislocates, the more stretched and lax the supporting ligaments become, making the chances of another dislocation higher over time. This is why it’s so important to not ignore your symptoms and to complete an effective rehab programme to strengthen the muscles that stabilise your knee cap.
Why does your knee cap dislocate?
There are two main types of patellar instability, the first is caused by a direct injury to the ligaments around your knee cap. This tends to be a sporting injury where the knee cap has received a blow on the side, causing it to move sideways either fully or partially (subluxation) out of its groove. This will lead to some ligament damage and laxity.
The second type of instability is due to an underlying structural issue that predisposes you to excessive movement of your kneecap in its groove. You might have a shallower groove in your thigh bone or your knee cap might be very small or located very high up in front of your knee (patella alta). If your thigh muscles are weak or you have hyper mobility syndrome, where your ligaments are naturally quite lax, these are also common causes.
Best treatment for patellar instability
If you have experienced a dislocation, your knee will likely swell for a few days and feel stiff and painful. Depending on the severity of the dislocation some people are issued with a knee brace. The length of time this is worn for varies from person to person and will be decided by a consultant.
In the early stages after a dislocation you will need to rest your knee and allow it to heal. Pace your activites and avoid things that cause pain. Take any medication which is prescribed for pain relief or to reduce swelling and apply an ice pack regularly for up to 20 minutes, three times per day.
If walking is uncomfortable try using a walking stick or hiking pole for a few days, holding it the opposite side to your affected knee.
Early stage exercises for patellar instability
Knee bends
Sit in a chair or lie down on your back with your leg straight. Bend your knee as far as comfortable.. Repeat 5-10 times. Do not push through pain.
Knee press
Press the back of your knee into the floor and hold for 5 seconds then relax. Repeat 5-10 times.
A physiotherapist will be able to guide you through a rehab programme of exercises to restore movement, strength and control around your knee. Some people do require surgery following patellar dislocation but this is normally only considered if you have not been successful following an appropriate programme of strength and conditioning exercises for at least 3 months.
