Patellar dislocation
Patellar dislocation
Patellar dislocations are comparatively common, with an incidence of 7 per 100,000 people, and affect above all younger people, mostly with an average age of about 21. The first dislocation is frequently an injury. Afterwards, 30 to 50 % of patients report a persisting feeling of instability and persisting pain at the front of the knee.
In 90 % of cases the first dislocation occurs after a minor incident – that is, there is no fall and no direct force, such as contact with an opponent in sport. The reasons for this usually lie in one or more underlying anatomical features of the knee joint, or even of the whole thigh or lower leg.
A precise analysis is therefore very important when recommending treatment. At Sportklinik Freiburg several hundred procedures to stabilise the patella, and revision procedures after earlier operations, are carried out every year.
What happens in a patellar dislocation?
Definition
A patellar dislocation means the kneecap (patella) coming completely out of its groove (the trochlea femoris) on the thigh bone. The kneecap mostly leaves the groove towards the outside (laterally). This can lead to irritation of the knee joint, swelling, pain and an inability to move the joint. In most cases it is an acute first dislocation, but it can also recur.
Causes
A patellar dislocation can arise through injury or through anatomical factors:
- A first dislocation caused by an accident (a twisting fall during sport, for example)
- A flat or dysplastic trochlea (the groove)
- A high-riding kneecap (patella alta)
- An increased Q angle or a valgus leg axis
- Hypermobility (with a weakness of the connective tissue, for example)
- Rotational deformity of the thigh (increased internal rotation, for example)
- A combination of injury and anatomical predisposition
How serious is it?
Medically, patellar dislocation can be divided into different grades of severity according to the accompanying injuries and the instability
- A first dislocation without lasting damage
Usually caused by an injury, with the kneecap returning to place spontaneously and no lasting damage. - A first dislocation with structural damage
For example with a tear of the MPFL (the medial patellofemoral ligament) or fragments of cartilage breaking off. - Habitual or recurring dislocations
The kneecap comes out repeatedly, often during everyday movements – a sign of chronic instability.
Potential for healing
The potential for healing after a patellar dislocation depends largely on the type of injury and on the anatomy.
- After a first dislocation without structural damage there is good potential for healing with non-surgical treatment – particularly in patients who are active in sport and whose joint is stable.
- Where the kneecap dislocates repeatedly, or there is accompanying damage (an MPFL rupture or cartilage injuries, for example), surgery is frequently necessary – an MPFL reconstruction, a medialising tibial tubercle transfer or a trochleoplasty.
- With consistent aftercare and an individually tailored rehabilitation plan, full fitness for sport can be regained in many cases.
Symptoms
The kneecap out of place
The kneecap visibly leaves the knee joint towards the outside and can catch there
Effusion
The tearing of the ligaments and any cartilage damage lead to fluid in the joint
Pain
The dislocation is very painful. Any cartilage damage hurts under load
The knee joint in detail
Rotate the 3D model and explore the structures
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Treatment options for a patellar dislocation
Treatment options
Non-surgical and surgical – we will find the right approach for you
Physiotherapy
Improving movement, strength and coordination
Treatment with a brace
Special supports stabilise the patella
Medication
Anti-inflammatory and pain-relieving medication (only to treat acute pain)
MPFL reconstruction
A ligament reconstruction from the patient's own tendon – stabilises the tracking of the patella in extension
Lengthening the lateral retinaculum
A Z-plasty, which lengthens the capsule and ligaments
Tibial tubercle transfer
The attachment of the extensor mechanism on the lower leg is moved, shifting the patella downwards or inwards
Osteotomy
A procedure on the bone of the thigh, correcting a knock knee or an inward rotation
Trochleoplasty
Correction of the groove on the thigh bone – improves the tracking of the patella in flexion
Our knee specialists
Experienced consultants for patellar dislocation and knee surgery
