Lying Hip Internal Rotation Test: Purpose, Procedure, and Interpretation

How do you do a lying hip internal rotation test?

The lying hip internal rotation test is a common assessment used to evaluate the passive range of motion and potential restrictions within the hip joint's internal rotation, performed with the individual supine and the hip and knee flexed to 90 degrees.

Understanding Hip Internal Rotation

Hip internal rotation is a fundamental movement where the anterior surface of the thigh rotates medially (inward) towards the midline of the body. This motion occurs at the ball-and-socket hip joint, involving the rotation of the femoral head within the acetabulum of the pelvis. It is a critical component of many daily activities and athletic movements, including walking, running, squatting, and pivoting.

Why Perform the Lying Hip Internal Rotation Test?

Assessing hip internal rotation is vital for several reasons:

• Identifying Mobility Restrictions: Limited hip internal rotation can indicate joint capsule tightness, muscular imbalances (e.g., overactive external rotators), or structural issues within the hip.
• Assessing Injury Risk: Restricted hip mobility, particularly internal rotation, has been linked to various lower extremity dysfunctions, including femoroacetabular impingement (FAI), patellofemoral pain syndrome, IT band syndrome, and lower back pain, as it can alter biomechanics during movement.
• Guiding Exercise Prescription: Understanding a client's or patient's hip mobility helps in designing appropriate exercise programs, including stretching, strengthening, and movement pattern correction.
• Performance Enhancement: Adequate hip internal rotation is crucial for optimal athletic performance, allowing for efficient force transfer and powerful rotational movements.

Anatomy Involved

The primary structures involved in hip internal rotation and this test include:

• Hip Joint: The articulation between the head of the femur and the acetabulum of the pelvis.
• Joint Capsule and Ligaments: The strong fibrous capsule and surrounding ligaments (iliofemoral, pubofemoral, ischiofemoral) that provide stability and limit excessive motion.
• Muscles: While internal rotation is often assisted by various muscles depending on hip position, the primary internal rotators in this flexed position include the anterior fibers of gluteus medius and minimus, and to a lesser extent, the tensor fascia latae (TFL) and some adductor muscles. The test also assesses the extensibility of the external rotators (e.g., piriformis, obturators, gemelli, quadratus femoris).

Step-by-Step Guide: Performing the Lying Hip Internal Rotation Test

This test is typically performed passively by an assessor, but the principles can be understood for self-assessment.

Preparation

1. Client Positioning: Have the individual lie supine (on their back) on a firm surface, such as an examination table or the floor. Ensure their spine is neutral and their pelvis is level.
2. Assessor Positioning: Position yourself beside the leg you are testing, at the level of the knee.
3. Limb Positioning: Flex the client's hip to 90 degrees and their knee to 90 degrees. The lower leg should be perpendicular to the floor.

Execution

1. Stabilize the Pelvis/Femur: This is the most crucial step to ensure an accurate measurement. Place one hand on the client's anterior superior iliac spine (ASIS) or across the pelvis to prevent any compensatory pelvic rotation or hip abduction/adduction. Alternatively, you can use your forearm to stabilize the distal thigh/femur just above the knee.
2. Grasp the Ankle/Lower Leg: With your other hand, gently grasp the client's ankle or distal lower leg.
3. Perform Passive Internal Rotation: Slowly and smoothly rotate the client's lower leg laterally (away from the midline of the body). As the lower leg moves laterally, the femur internally rotates within the hip joint. Continue until you feel a firm but yielding end-feel, indicating the limit of the passive range of motion. Do not force the movement.
4. Observe/Measure the Angle: At the end-range, observe the angle that the lower leg makes relative to a vertical line perpendicular to the floor.
   • Visual Estimation: For a quick assessment, simply observe the relative angle.
   • Goniometer Measurement: For a precise measurement, place the fulcrum of a goniometer over the patella (or the anterior aspect of the knee joint line). Align the stationary arm perpendicular to the floor (or parallel to the femur if stabilizing the thigh). Align the moving arm with the crest of the tibia or the midline of the lower leg, pointing towards the ankle. Read the angle.
5. Repeat on Opposite Side: Perform the exact same procedure on the other hip to compare sides.

Key Considerations

• Pelvic Stability: Emphasize maintaining a stable pelvis. Any lifting or tilting of the pelvis indicates compensation and an inaccurate measurement.
• Avoid Compensation: Ensure the client does not abduct or adduct the hip, or rotate their trunk during the test. The movement should be purely internal rotation at the hip.
• Smooth Movement: Perform the rotation slowly and gently to accurately identify the end-feel and prevent discomfort.
• End-Feel: Pay attention to the quality of the "stop." A firm, elastic end-feel is normal, while a hard, abrupt stop might indicate a bony block (e.g., FAI).

Interpreting the Results

Normal Range of Motion

• The typical healthy passive range of motion for hip internal rotation in the lying 90/90 position is generally 30 to 45 degrees. There can be slight variations based on age, sex, and individual anatomy.

Limitations/Asymmetries

• Reduced Range of Motion (Less than 30 degrees): This is a common finding and can indicate:
  • Tightness in the external rotator muscles (e.g., piriformis, obturator internus).
  • Tightness or restriction in the posterior aspect of the hip joint capsule.
  • Structural abnormalities like femoroacetabular impingement (FAI), particularly cam or mixed-type impingement.
  • Osteoarthritis.
• Excessive Range of Motion (Greater than 45 degrees): While less common, excessive motion might suggest:
  • Generalized ligamentous laxity.
  • A history of hip dislocation or instability.
• Asymmetry (Significant difference between sides): A difference of 10-15 degrees or more between the left and right hip can be clinically significant and may contribute to unilateral pain or compensatory movement patterns.

What to Do with the Results

The results of the lying hip internal rotation test provide valuable data for:

• Targeted Stretching: If limited, specific stretches for external rotators and hip capsule mobilizations can be prescribed.
• Strengthening Programs: Identifying imbalances can guide strengthening exercises for internal rotators or other hip musculature.
• Movement Pattern Correction: Understanding restrictions helps in correcting faulty movement patterns during functional activities or sports.
• Referral: If severe limitations, pain, or suspected structural issues are present, referral to a physical therapist, orthopedic surgeon, or sports medicine physician is warranted for further diagnostic evaluation.

Important Considerations and Limitations

• Not a Diagnostic Test Alone: This test is an assessment tool, not a standalone diagnostic test. Its findings should always be interpreted in conjunction with a comprehensive client history, other physical assessments, and functional movement screens.
• Inter-Rater Reliability: Accurate and consistent measurements require practice and experience, especially when using a goniometer.
• Influence of Other Factors: The perceived range of motion can be influenced by soft tissue restrictions, joint effusion, pain, and the client's willingness to relax.

Conclusion

The lying hip internal rotation test is a simple yet powerful tool for fitness professionals, kinesiologists, and healthcare providers to assess hip joint mobility. By understanding the proper execution and interpretation of this test, you can gain critical insights into a client's hip health, identify potential limitations, and design more effective, evidence-based exercise and rehabilitation programs. Always prioritize client comfort and safety, and refer to appropriate medical professionals when necessary.