Recurrent patella dislocation

Definition/diagnostic criteria Recurrent patella dislocation is characterised by repeated episodes of displacement of the patella from its normal position in the femoral trochlea. This condition is often associated with a high grade of patellofemoral dysplasia and may be traumatic or atraumatic in origin. The diagnostic criteria involve a history of patellar dislocation, usually lateral, confirmed by clinical examination and imaging studies.

Epidemiology Recurrent patella dislocation is more common in adolescents, females and individuals engaged in high-impact sports.

Diagnosis
Clinical features: Patients typically present with a history of patellar instability, which includes a feeling of the knee ‘giving way’ or actual episodes of the patella dislocating. Pain, swelling and apprehension with certain movements, such as squatting or twisting motions, are also common. The apprehension test, where the patella is gently pushed laterally and the patient experiences fear of dislocation, is a key sign.

Investigations: Diagnosis is confirmed through imaging.

• X-ray may show a high-riding patella (patella alta) or trochlear dysplasia.
• MRI is the most useful tool for assessing the soft tissue restraints of the patella and the morphology of the trochlea.
• Typical abnormalities found on MRI include the presence of bone bruising, osteochondral injuries and damage to the medial patellofemoral ligament (MPFL).

Treatment The treatment of recurrent patella dislocation is primarily based on the severity and frequency of dislocations, patient age and level of activity

Conservative management: Initial management is typically non-surgical, focusing on reducing acute symptoms with rest, ice, compression and elevation (RICE), followed by a structured rehabilitation programme aimed at strengthening the quadriceps, particularly the vastus medialis oblique muscle, and improving patellofemoral mechanics.

However you should refer urgently for specialist assessment if first-time traumatic patellar dislocation is suspected, or a recurrent dislocation is associated with moderate or severe swelling.

Surgical intervention: Surgery may be considered in recurrent or persistent cases, particularly in the presence of significant anatomical abnormalities. Procedures include medial patellofemoral ligament reconstruction, tibial tubercle transfer, or trochleoplasty, tailored to the individual’s specific pathology.

Prognosis The prognosis for recurrent patella dislocation is variable and depends on the underlying cause and the effectiveness of treatment. With appropriate management, many individuals can return to their previous levels of activity. However, recurrent dislocations can lead to chronic pain and predispose individuals to patellofemoral arthritis.