Patellofemoral Instability: Etiology, Clinical Presentation and Management

The patellofemoral joint is composed of the patella (kneecap) and the femoral trochlea, the groove in which the patella glides during knee motion. In the presence of instability, the patella may deviate or dislocate from this groove, resulting in anterior knee pain and functional limitation during activities such as stair climbing or walking. Patients often report a sensation of the knee “giving way” or the patella “shifting out of place.”

Etiological Factors

Several factors can contribute to patellofemoral instability, including:

• Anatomical malalignment (trochlear dysplasia, patella alta, increased Q-angle, or rotational deformities), which alter patellar tracking within the trochlea;

• Muscular imbalance or weakness, particularly of the quadriceps (especially the vastus medialis obliquus) and hip stabilizers (gluteus medius and external rotators), compromising dynamic stability;

• Traumatic injuries, such as direct impact or torsional mechanisms, which may lead to acute patellar dislocation and damage to the medial patellofemoral ligament (MPFL).

Clinical Presentation

Common symptoms include:

• Anterior knee pain;

• Apprehension or a sensation of patellar subluxation/dislocation;

• Crepitus, joint effusion, or mechanical locking after activity.

Diagnosis

Diagnosis is based on clinical assessment, including movement analysis, apprehension tests, and evaluation of lower limb alignment. Radiographic imaging and magnetic resonance imaging (MRI) may be indicated to assess bone morphology, cartilage condition, and soft-tissue injury (e.g., MPFL tear).

Management

In most cases, conservative management is the first-line approach, focusing on:

• Physiotherapy aimed at strengthening the quadriceps and hip musculature, improving neuromuscular control, and correcting biomechanical deviations;

• Flexibility training of the posterior chain muscles to optimize lower limb kinematics;

• Use of patellar taping, bracing, or orthoses to enhance tracking during rehabilitation.

Surgical intervention (e.g., MPFL reconstruction, tibial tubercle transfer, or trochleoplasty) may be considered in recurrent or severe cases, depending on anatomical abnormalities and instability severity.

Prevention

Preventive strategies include maintaining adequate muscle strength and flexibility, optimizing lower limb alignment, and avoiding sedentarism. Early physiotherapy intervention is essential to prevent recurrence and restore functional stability.