What is it called when the quadriceps tendon ruptures and there is no ability to palpate it?

Palpable Gap Sign

The clinical finding you're describing—when the quadriceps tendon ruptures and there is no ability to palpate it—is called a "palpable gap" or "palpable defect" in the suprapatellar region. This is a classic physical examination finding that, combined with inability to perform a straight leg raise, is diagnostic of complete quadriceps tendon rupture 1, 2, 3, 4.

Key Clinical Features

The diagnostic triad for quadriceps tendon rupture consists of:

• Sudden suprapatellar pain following eccentric contraction or trauma
• Palpable gap or defect above the patella where the tendon should be
• Complete inability to perform active knee extension (straight leg raise)

The palpable gap represents the physical separation between the torn tendon ends, creating an area where normal tendon continuity is absent 1, 2, 4. This finding is particularly prominent in complete ruptures and may be less obvious in partial tears.

Clinical Examination Pearls

When examining for this finding:

• Palpate the suprapatellar region systematically with the knee in slight flexion to relax surrounding tissues
• Compare to the contralateral knee to identify asymmetry
• Look for associated findings: significant swelling in the distal thigh anteriorly, absent patellar reflex, and patella baja on lateral radiographs (patella sits lower than normal) 1, 3

Important Caveats

Be aware that the palpable gap can be masked or missed in several scenarios:

• Significant swelling or hematoma may obscure the defect, especially in acute presentations 2
• Distracting injuries (such as concurrent fractures) may draw attention away from the knee examination 2
• Initial immobilization with long-leg splints can mute knee symptoms and make the gap harder to appreciate 2
• Chronic ruptures may have scar tissue filling the gap, making it less palpable 5

Maintain a high index of suspicion when patients present with suprapatellar pain and inability to extend the knee, even if the gap is not immediately obvious. Repeated clinical examinations may be necessary, particularly in the presence of distracting injuries 2.

Diagnostic Confirmation

While the palpable gap combined with loss of active extension is often sufficient for clinical diagnosis, imaging can confirm uncertain cases 1:

• Lateral knee radiographs (soft tissue technique) reveal the defect and show patella baja
• Ultrasound can directly visualize the tendon disruption and gap 6, 1
• MRI provides definitive diagnosis when clinical examination is equivocal 1