Patellar Glide Test: Purpose, Procedure, Interpretation, and Clinical Significance

What is the Patellar Glide Test?

The patellar glide test is a manual orthopedic assessment used to evaluate the mobility and tracking of the patella (kneecap) within the trochlear groove of the femur, helping to identify potential causes of anterior knee pain and patellofemoral dysfunction.

Understanding the Patellar Glide Test

The patellar glide test is a fundamental examination technique employed by healthcare professionals, including physical therapists, orthopedic surgeons, and sports medicine physicians, to assess the health and function of the patellofemoral joint. This test provides crucial insights into the mobility of the patella in various directions, which is essential for proper knee mechanics and pain-free movement.

Anatomy of the Patellofemoral Joint

To fully appreciate the patellar glide test, a brief review of the relevant anatomy is beneficial:

• Patella (Kneecap): A sesamoid bone embedded within the quadriceps tendon, acting as a fulcrum to increase the mechanical advantage of the quadriceps muscle.
• Femur (Thigh Bone): Specifically, the distal end of the femur features a groove called the trochlear groove or patellofemoral groove, where the patella articulates.
• Articular Cartilage: Both the posterior surface of the patella and the trochlear groove are covered with smooth articular cartilage, allowing for low-friction gliding.
• Quadriceps Tendon & Patellar Ligament: The quadriceps muscles connect to the patella via the quadriceps tendon, and the patella connects to the tibia via the patellar ligament (often called the patellar tendon).
• Retinaculum: Medial and lateral retinacula are fibrous tissues that help stabilize the patella within the trochlear groove.

During knee flexion and extension, the patella should glide smoothly within the trochlear groove. Any disruption to this smooth motion can lead to pain and dysfunction.

The Mechanics of Patellar Tracking

Patellar tracking refers to the path the patella takes as the knee bends and straightens. Optimal tracking involves the patella staying centered within the trochlear groove. Factors that can influence patellar tracking include:

• Muscle Imbalances: Weakness or tightness in the quadriceps (e.g., vastus medialis obliquus vs. vastus lateralis), hamstrings, or hip abductors/adductors.
• Ligamentous Laxity or Tightness: Issues with the medial or lateral retinaculum.
• Bony Anatomy: Variations in the depth of the trochlear groove or the shape of the patella.
• Q-angle: The angle formed by the quadriceps muscle and the patellar ligament, which can influence lateral pull on the patella.
• Foot Mechanics: Overpronation can lead to internal rotation of the tibia, affecting patellar alignment.

Abnormal tracking can result in increased stress on the patellofemoral joint, leading to conditions like patellofemoral pain syndrome (PFPS) or chondromalacia patellae.

Performing the Patellar Glide Test

The patellar glide test is performed with the patient in a relaxed position, typically supine (lying on their back) with the knee extended or in slight flexion (around 20-30 degrees) to relax the quadriceps.

1. Patient Positioning: The patient lies supine with the involved knee relaxed. The examiner may support the knee in slight flexion (e.g., using a towel roll) to allow for quadriceps relaxation.
2. Examiner Hand Placement: The examiner gently grasps the patella between their thumb and index finger, or with the web space of their hand, ensuring a firm but non-painful grip.
3. Glide Directions: The examiner then attempts to glide the patella in four primary directions:
   • Medial Glide: Pushing the patella directly towards the inner side of the knee.
   • Lateral Glide: Pushing the patella directly towards the outer side of the knee.
   • Superior Glide (Proximal): Pushing the patella upwards, towards the hip.
   • Inferior Glide (Distal): Pushing the patella downwards, towards the foot.
4. Assessment Criteria: During each glide, the examiner assesses:
   • Amount of Movement: How far the patella moves relative to its starting position. This is often measured in "quadrants" (e.g., 1/4, 2/4, 3/4, or 4/4 of its width).
   • End-Feel: The quality of resistance felt at the end of the movement (e.g., firm, soft, empty).
   • Pain Response: Any pain elicited or reproduced during the glide, noting its location and intensity.
   • Crepitus: Any grinding or crunching sensations.

The uninvolved knee is often tested first for comparison, establishing a baseline for the individual.

Interpreting Findings and Clinical Implications

The interpretation of the patellar glide test is crucial for diagnosis and treatment planning:

• Normal Mobility: Typically, the patella should glide approximately 1-2 quadrants (about half its width) in medial and lateral directions, and a similar amount superiorly and inferiorly, without pain. The end-feel should be firm but yielding.
• Hypomobility (Restricted Glide): Reduced movement in any direction suggests tightness or adhesions.
  • Restricted Lateral Glide: May indicate tightness of the lateral retinaculum or vastus lateralis, common in patellofemoral pain syndrome.
  • Restricted Medial Glide: Less common, but could indicate tightness of the medial retinaculum.
  • Restricted Superior/Inferior Glide: May be due to quadriceps contracture, patellar tendon tightness, or adhesions post-surgery.
• Hypermobility (Excessive Glide): Increased movement beyond normal limits.
  • Excessive Lateral Glide: Suggests laxity of the medial retinaculum, often associated with patellar instability, subluxation, or dislocation.
  • Excessive Medial Glide: Less common, but can also indicate instability.
  • Excessive Superior/Inferior Glide: Could indicate generalized ligamentous laxity or a high-riding patella (patella alta) or low-riding patella (patella baja) respectively.
• Pain Response: Pain elicited during a specific glide direction, especially if it reproduces the patient's chief complaint, is highly significant. For instance, pain with lateral glide often points to lateral patellar compression syndrome.

Clinical Significance and Limitations

The patellar glide test is a valuable tool for:

• Diagnosing Patellofemoral Pain Syndrome (PFPS): Identifying specific areas of tightness or instability contributing to pain.
• Assessing Patellar Instability: Detecting excessive lateral mobility, which can predispose to subluxation or dislocation.
• Monitoring Treatment Progress: Tracking changes in patellar mobility over time with physical therapy interventions.
• Pre- and Post-Surgical Assessment: Evaluating patellar mechanics before and after knee surgery.

However, it's important to note the limitations of the test:

• Subjectivity: The assessment of "normal" versus "abnormal" glide can be subjective and vary between examiners.
• Not a Standalone Diagnostic Tool: Findings from the patellar glide test must always be correlated with the patient's history, other orthopedic tests, and imaging studies for an accurate diagnosis.
• Patient Relaxation: The accuracy of the test relies heavily on the patient's ability to relax the quadriceps muscles.

Conclusion

The patellar glide test is a cornerstone of patellofemoral joint assessment, offering critical information about patellar mobility and its potential role in knee pain and dysfunction. While a powerful diagnostic aid when performed correctly and interpreted within a broader clinical context, it is one piece of a comprehensive orthopedic examination. Understanding its principles and implications allows fitness professionals to better appreciate the complex biomechanics of the knee and guides healthcare providers in developing targeted, evidence-based treatment strategies for individuals experiencing anterior knee pain.