Posterolateral instability of the knee

Area of Science:

• Orthopedics
• Sports Medicine
• Knee Biomechanics

Background:

• Posterolateral knee instability presents diagnostic and therapeutic challenges.
• It is frequently linked to ligament reconstruction failures and multiple surgical interventions.
• Patients often report a sensation of the knee giving way.

Purpose of the Study:

• To describe a specific presentation of posterolateral knee instability.
• To introduce a novel diagnostic test for this condition.
• To investigate the underlying biomechanical factors and associated symptoms.

Main Methods:

• Evaluation of a small cohort of patients with subjective knee instability.
• Clinical examination including assessment of tibial external rotation at 90 degrees knee flexion.
• Description and application of a novel standing apprehension test.
• Radiographic and MRI confirmation of suspected bony abnormalities.

Main Results:

• Patients exhibited increased tibial external rotation at 90 degrees knee flexion.
• The described standing apprehension test was positive in all evaluated patients.
• Anterior subluxation of the lateral femoral condyle was identified in four patients.
• Medial knee pain was a common associated symptom, potentially linked to soft tissue or nerve stretching.

Conclusions:

• Posterolateral knee instability can manifest with specific clinical signs, including increased external tibial rotation.
• The standing apprehension test may aid in diagnosing this condition.
• Anterior subluxation of the lateral femoral condyle is a potential finding in these patients.
• Medial knee pain may be referred pain from posteromedial structures or nerve irritation.