First-Time Patellar Dislocation — What Should You Do?

Polish version · Explore Knee Conditions

A first-time patellar dislocation requires assessment even if the patella has moved back into place on its own. It is important to exclude an osteochondral fragment, assess the structures that stabilise the patella and determine whether the anatomy of the knee increases the risk of another dislocation. Many patients begin with non-operative treatment, but not every first dislocation is the same.

What happens during a patellar dislocation?

The patella usually moves towards the outside of the knee. The injury may occur during a twist on a weight-bearing leg, a sudden change of direction or a direct blow. Sometimes the patella remains visibly out of its normal track, but it often reduces spontaneously as the knee straightens or before medical assessment.

The medial soft tissues that stabilise the patella are commonly injured during the displacement, including the medial patellofemoral ligament (MPFL). Bone bruising, cartilage injury or detachment of an osteochondral fragment into the joint can also occur.

What should you do immediately after the injury?

If the patella is still visibly displaced, the knee is deformed or cannot be moved, urgent medical assessment is needed. Do not force the knee into flexion or repeatedly attempt to reduce the patella yourself. Support the limb in the least painful position.

If the patella has reduced spontaneously, cooling through a cloth, reduced loading and crutches when walking is painful may help initially. Disappearance of the deformity does not exclude an injury inside the joint. A rapidly developing knee effusion can indicate bleeding or an osteochondral injury, among other causes.

What symptoms are typical after a dislocation?

• pain and tenderness along the medial side of the patella;
• swelling or bruising around the knee;
• a sense of instability or fear that the patella may “pop out” again;
• pain during knee flexion and extension;
• difficulty bearing weight;
• locking or catching if a loose fragment is present in the joint.

Anterior knee pain may persist after the acute phase. This does not automatically mean that another dislocation has occurred, but it may require assessment of patellar tracking, muscle strength and possible cartilage injury.

How is a first-time patellar dislocation assessed?

History and examination

Age, the injury mechanism, previous episodes of the patella “giving way”, similar symptoms in the other knee and a family history of instability can all be relevant. The examination assesses effusion, tenderness, the ability to extend the knee, ligament stability and patellar position. In the acute phase, severe pain can limit the accuracy of some tests.

X-ray

Radiographs are obtained to confirm patellar alignment, exclude a fracture and look for a visible bony fragment. A normal X-ray does not exclude cartilage injury or a small osteochondral fragment.

MRI

The current ESSKA consensus recommends early MRI after a first-time dislocation, apart from the exceptional situation of an asymptomatic patient. MRI can identify cartilage injury, a loose fragment and MPFL injury, and it can demonstrate anatomical features associated with recurrence such as trochlear dysplasia and patella alta. The findings also help guide subsequent treatment.

When is CT needed?

CT is not required for every patient. It may be useful for more detailed assessment of a bony fragment, fracture or three-dimensional anatomy, particularly when surgery is being considered.

Is a first dislocation usually treated without surgery?

Often yes, but the decision should not be based simply on the number of previous dislocations. If there is no large osteochondral fragment, no clear injury requiring repair and no very high risk of recurrence, treatment usually includes a short period of knee protection, gradual restoration of movement and rehabilitation.

A brace may improve confidence in the early period, but there is no strong evidence that prolonged bracing alone reduces recurrence risk. Excessive immobilisation can contribute to stiffness and quadriceps weakness.

What does rehabilitation involve?

The programme is adapted to pain, swelling and stability. The first goals are to restore safe extension and flexion and a normal gait. Rehabilitation then focuses on quadriceps and hip strength, control of lower-limb alignment and balance. Return to running, cutting movements and sport requires recovery of range of motion, strength and control comparable with the other leg — the passage of a few weeks alone is not enough.

When is surgery considered after a first dislocation?

• when a significant osteochondral fragment has detached and requires fixation or repair of the joint surface;
• when a loose fragment inside the joint causes locking;
• when the risk of another dislocation is high because of age, symptoms and anatomical abnormalities;
• when clear instability persists despite appropriate treatment;
• after recurrent dislocations.

If surgery addresses the medial stabilising structures, current consensus favours MPFL reconstruction over simple ligament repair. In selected patients, an important bony risk factor may need to be corrected at the same time, but surgical thresholds are not identical for every patient and remain an area of discussion.

How high is the risk of recurrence?

The ESSKA consensus cites a recurrence rate of about 25% after a first-time dislocation. Risk is not the same for everyone. It is higher with younger age, skeletal immaturity, trochlear dysplasia, patella alta, previous symptoms of instability and the coexistence of several risk factors.

Not having another complete dislocation does not always mean full recovery. Up to half of patients may report persistent pain, swelling, a sense of the knee giving way, functional limitations or fear of returning to sport. Treatment outcome therefore needs to be assessed more broadly than by recurrence alone.

Warning signs

• the patella remains out of position or the knee is visibly deformed;
• the foot is pale, cold or numb, or cannot be moved normally;
• the knee cannot be straightened or the straight leg cannot be lifted;
• the knee rapidly fills with blood, locks or does not allow weight bearing;
• pain and swelling are clearly increasing rather than gradually settling.

Key points for an orthopaedic surgeon

After a first-time patellar dislocation, assessment should consider not only whether the patella has returned to place, but also the cartilage, bone, MPFL and factors that increase recurrence risk. Most uncomplicated injuries can begin with non-operative treatment and targeted rehabilitation. An osteochondral fragment, locking or a high risk of another dislocation can, however, change management after the first episode.

References

1. Blønd L et al. Management of first-time patellar dislocation: The ESSKA 2024 formal consensus—Part 1. Knee Surgery, Sports Traumatology, Arthroscopy. 2025;33(5):1925–1932. DOI: 10.1002/ksa.12620. PubMed.
2. Balcarek P et al. Management of first-time patellar dislocation: The ESSKA 2024 formal consensus—Part 2. Knee Surgery, Sports Traumatology, Arthroscopy. 2025;33(12):4197–4206. DOI: 10.1002/ksa.12637. PubMed.

Content prepared by: Tomasz Poboży - orthopaedic surgeon.