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Patella (Knee Cap) Dislocation
Your patella (also called knee cap) slides up and down in a groove at the end of the thigh bone, your femur.
Dislocation is when the patella comes out of this groove that it usually sits in.
There are a few causes of patella dislocation:
Trauma
Caused by impact, often when playing sports like rugby or football, or when changing direction suddenly when playing sport.
Non-trauma
If there has been no traumatic cause, your patella may have dislocated due to some pre-disposing factors, such as:
- If you’re extra flexible.
- If you have a shallow or altered shape groove for the patella to sit in—this is called trochlea dysplasia.
- Previous injury / trauma / previous dislocation without sufficient rehabilitation.
- If your body shape has an increased angle between your hips and knees—much more common in girls.
- Muscle length and strength imbalance which can cause the muscles to pull the patella at a different angle.
- A patella that sits unusually high—patella alta.
How does the knee cap become dislocated?
Your patella is most likely to dislocate to the side. Often it will come back into the groove on its own when you then straighten the knee.
Occasionally this isn’t the case and a medical professional may have to help you to re-locate it.
When the patella moves laterally out of the groove, this causes the ligament on the inner side of your knee to be stretched which can be sore for a little while afterwards when your patella is relocated.
If you have any concerns or queries about this information please contact Dolphin Outpatients on 02921 847577.
If your child does not have an appointment arranged with physio and symptoms continue or are not improving gradually, then you can self-refer your child to the Paediatric Physiotherapy Outpatient Department by telephoning the our referral line on 02921 836908.
Signs and symptoms
Initial treatment
What happens next?
Pain Relief
Exercises
Signs and symptoms
Immediately after the dislocation you should expect:
- Swelling that occurs in the first few minutes to hours after the injury. This swelling is caused by the body’s healing response to the soft tissue damage
- Pain and tenderness around the knee joint and usually around the inner side and the front of the knee. It may be too painful to put weight on the leg immediately after.
- Range of movement may be effected initially as it may be difficult to fully straighten your knee at first and you may feel a little nervous of bending your knee.
Initial treatment
Following the dislocation, it is best to start treatment immediately following the principles of P.O.L.I.C.E (Protection, Optimal Loading, Ice, Compression, Elevation). This will help to reduce the swelling and aid healing.
Protection: It is important to protect the injured area to avoid further tissue damage. This may mean using crutches, or a brace for a short while.
Optimal Loading: Optimal loading will enhance the healing process, and help to reduce swelling. For example, weight bearing when walking encourages the muscles to contract and therefore will minimise swelling at the affected knee.
Ice: Use ice on the affected area for 10-15mins at a time, every 2-3 hours during the day. Make sure that you allow the knee to return to normal temperature before reapplying an ice pack. Ensure you protect the skin from ice burns by keeping a barrier between your skin and the ice, like a tea towel or pillow case etc.
Compression: Compression bandages can be worn to help reduce the swelling, making sure that you can still move your knee and the circulation is still intact.
Elevation: When resting keep your ankle elevated on pillows so that it is higher than the rest of your leg. This enables gravity to help with reducing the swelling.
What happens next?
Often, if you attend A&E after the dislocation, they will put you in a brace that prevents you from moving your knee. Ideally you should only be in this brace for a couple of days at most because it is very important to get your knee moving again as soon as possible.
When you come to trauma clinic, the consultant will decide if it is necessary for you to have a different type of brace that is specifically for patella dislocations. This brace will allow you to bend and straighten your knee but gives your patella some extra support.
You may be given crutches to help you walk, it is important that you still put weight through the leg (unless specifically told not to by your consultant), to prevent weakness, stiffness and delays in healing.
Pain Relief
It is normal to experience mild pain and some children will require pain relief like Paracetamol or anti-inflammatories such as ibuprofen.
See NHS guidelines here on pain relief.
You can also seek advice from your local pharmacy.
Exercises
The MOST IMPORTANT part of your rehab after this injury is to get your quadriceps (the big muscles in your thigh) as strong as possible to minimise the chances of future re-dislocations.
Range of Movement Exercises
Firstly it is important to re-gain full range of movement at your knee, so practice gently bending and straightening your knee in sitting and in laying.
You can use your other leg to help push a bit further into a stretch.
Strengthening Exercises
These can be done with your patella brace on at first until you feel more confident.
Static Quads: Lying or sitting with your legs straight, push the back of your knee down into the floor/ bed as tight as you can, bringing your toe up towards you. Hold for 5 seconds, then relax. Repeat 10 times.
Inner Range Quads: Roll up a large towel or use a round cushion to place under your knee. Push the back of your knee down into the roll as tight as you can, so that your heel comes up from the floor/bed. Hold for 5 seconds, then relax. Repeat 10 times.
Straight Leg Raise: Push the back of your knee down so your knee is completely straight, then slowly and controlled lift your whole leg from the floor/bed, keeping it completely straight. Lift as high as is comfortable, hold for 3-5 seconds and then slowly lower the leg back down. Repeat 8 times.
These are some simple exercises to get you started which are very important building blocks for your ongoing rehab. Make a good start with these as soon as possible after injury and your physiotherapist will guide you through how to progress.
If you have any concerns or queries about this information please contact Dolphin Outpatients on 02921 847577.
If your child does not have an appointment arranged with physio and symptoms continue or are not improving gradually, then you can self-refer your child to the Paediatric Physiotherapy Outpatient Department by telephoning the our referral line on 02921 836908.
