Telescopy Test & Pediatric Telescope Sign

Telescopy Test is an important clinical orthopedic examination used to evaluate the stability of the hip joint most commonly in conditions such as Developmental Dysplasia of the Hip (DDH). This physical test helps examiners detect abnormal movement of the femoral head within the acetabulum and is especially useful in pediatric and orthopedic evaluations. It’s also known as the piston test.

This test is most commonly applied in:

• Developmental dysplasia of the hip (DDH)
• Congenital hip dislocation
• Post-traumatic or post-surgical hip instability (less commonly)

How do you perform the Hip Telescopy Test?

• The patient is positioned supine on the examination table, and this is better done with the examiner standing on the side that is to be examined.
• The hip and knee are flexed to 90° and the hip kept in mild adduction.
• The pelvis is supported with one hand by placing the thenar eminence over the anterior superior iliac spine ASIS and the fingers on the greater trochanter.
• The knee/ distal thigh is held with the other hand, and a gentle push and pull force is applied along the long axis of the thigh.
• The examiner assesses the vertical movement of the femur relative to the pelvis.

The hip and knee should have flexion range of movement; adduction should be possible at hip, firm mattress, ideally a painless hip.

See Also: 

• Trendelenburg test
• Thomas Test
• Hip Joint Anatomy

What does a positive Telescopy Test mean?

A positive telescopy test is indicated by:

• Apparent limb shortening that corrects with traction
• Excessive up-and-down movement of the femur
• A sensation of the femoral head sliding in and out of the acetabulum

When the excursion is more than that compared to the other side, think of conditions like a femoral neck fracture nonunion, hip dislocation, old unreduced posterior hip dislocation, dislocated total hip replacement.

Pediatric Telescope Sign

The Pediatric Telescope Sign indicates the congenital hip dislocation in pediatric patients. It’s performed as following:

The examiner grasps the affected leg with one hand and passively flexes the hip and knee. The other hand rests posterolateral to the hip. The examiner palpates the greater trochanter with the thumb of this hand and the motion of the femoral head with the index finger. The hand guiding the leg alternately applies axial compression and traction to the femur.

In a hip dislocation, the leg will appear to shorten or lengthen. The palpating hand follows the motion of the greater trochanter and femoral head into the dislocated position and back to reduction.

What are the causes of a telescoping hip?

Telescoping hip (positive Telescopy Test) can be caused by multiple conditions:

1. Girdlestone arthroplasty.
2. Old unreduced dislocation with lax structures.
3. Developmental Dysplasia of the Hip (DDH).
4. Pathological dislocation e.g. TB.
5. Charcot’s joint.
6. Perthes disease.
7. Slipped capital femoral epiphysis (SCFE) .
8. Squeal of septic arthritis.
9. Osteonecrosis with collapse.
10. TB hip: Mortar and pestle type, destroyed head, wandering acetabulum.
11. Non Union fracture neck femur.
12. Non Union fracture intertrochanteric.

Telescopy Test vs Other Hip Tests

Mechanisms and Diagnostic Focus

The Telescopy Test is specifically designed to assess vertical instability of the hip joint. By applying axial compression and traction, the examiner can detect abnormal up-and-down movement of the femoral head within the acetabulum. This makes the test particularly valuable for identifying dislocations or significant laxity, especially in pediatric cases or following trauma.

In contrast, the Pelvic Rocking Test evaluates general joint stability and the integrity of the pelvic and lower back region. During this test, the patient rocks their pelvis back and forth while lying supine. Pain or restricted motion may indicate joint injury or infection, but this test does not isolate vertical instability or specific dislocation as precisely as the telescopy test.

The Trendelenburg Sign serves a different purpose entirely. It assesses the strength of the hip abductor muscles, particularly the gluteus medius. A positive Trendelenburg sign—where the pelvis drops on the side opposite the stance leg—suggests abductor weakness, often seen in conditions like Trendelenburg gait, but does not directly evaluate joint stability or dislocation.

Clinical Decision-Making: Choosing the Right Test

Selecting the appropriate hip test depends on the clinical question at hand:

• Suspected Hip Dislocation or Instability: The telescopy test is preferred, as it directly evaluates vertical instability and abnormal femoral head movement.
• General Hip or Pelvic Pain: The pelvic rocking test is useful for identifying broad joint issues or infection when the source of pain is unclear.
• Abnormal Gait or Suspected Muscle Weakness: The Trendelenburg sign provides insight into abductor muscle function, helping differentiate muscular from structural causes of hip dysfunction.

Test	Primary Use
Ortolani Test	Detects reducible hip dislocation in infants
Barlow Test	Identifies unstable hips prone to dislocation
Telescopy Test	Assesses vertical instability and limb shortening
Galeazzi Sign	Detects limb length discrepancy

References

1. Clinical Tests for the Musculoskeletal System 3rd Edition.
2. Sarvdeep S. Dhatt, Sharad Prabhakar – Handbook of Clinical Examination in Orthopedics. An Illustrated Guide-Springer Singapore.
3. Clinical Assessment and Examination in Orthopedics, 2nd Edition Book.
4. The video from Youtube: https://www.youtube.com/watch?v=93pOrTcuiT4