Yes, This Could Be an Avulsion Injury
Acute groin and hip pain after a heavy squat with normal plain radiographs can absolutely represent an avulsion injury, and you should proceed with advanced imaging—specifically MRI—to establish the diagnosis. 1, 2
Why This Clinical Scenario Suggests Avulsion Injury
The mechanism you describe (heavy squat) involves extreme eccentric muscular contraction, which is the classic mechanism for avulsion injuries 3. The normal radiograph does not exclude this diagnosis because:
- Avulsion injuries are frequently radiographically occult, especially in the acute phase when only soft tissue injury or minimal bone fragment displacement has occurred 2, 3
- Adolescents and young athletes are particularly susceptible to these injuries at apophyseal sites due to relative weakness of growth cartilage 4
- Adults can sustain avulsions at tendinous insertions, particularly with underlying tendinosis or during high-force activities 4
The Imaging Algorithm
Step 1: Initial Radiography (Already Done)
While radiography is the appropriate initial study for acute traumatic hip pain 1, normal radiographs do NOT exclude avulsion injury 2, 5, 3. The ACR guidelines prioritize radiography first for acute traumatic hip pain to rule out fractures and dislocations 1, but this is just the starting point.
Step 2: MRI Without Contrast (Next Step)
When radiographs are normal but clinical suspicion remains high for avulsion injury, MRI is the definitive diagnostic modality 2, 5. MRI will reveal:
- Muscle edema and displacement at the injury site
- Interposed fluid at the bony attachment
- Critical finding: T1 hyperintensity (hemorrhage) deep to the displaced muscle, which confirms traumatic avulsion and distinguishes it from infection or inflammation 2
- Associated soft tissue injuries (tendon tears, muscle strains)
- Small bone fragments that are radiographically occult
Common Avulsion Sites After Squatting
Look for injuries at these specific locations:
- Lesser trochanter (iliopsoas insertion) - common in adolescents during forceful hip flexion 6
- Greater trochanter (gluteus medius/minimus) - can be radiographically occult 5
- Ischial tuberosity (hamstring origin)
- Anterior inferior iliac spine (rectus femoris) 7
- Obturator internus - rare but has a distinct MRI pattern with medial muscle displacement and bowing 2
Critical Pitfall to Avoid
Do not mistake subacute or chronic avulsion injuries for neoplasm or infection 3. Subacute injuries (days to weeks old) can show aggressive-appearing mixed lysis and sclerosis on imaging, while chronic injuries may present as protuberant bone masses 3. The key distinguishing feature is the history of acute trauma with a specific mechanism and the anatomic location corresponding to a known musculotendinous attachment site.
Management Implications
Most avulsion injuries in this setting are managed conservatively with:
- Protected weight-bearing
- Activity modification
- Physical therapy
- Return to sport typically at 1-2.5 years for complete avulsions 2
However, you need the MRI diagnosis first to:
- Confirm the injury type and extent
- Rule out complete tendon rupture requiring surgery
- Avoid unnecessary investigations for infection or tumor
- Guide appropriate rehabilitation protocols
Bottom line: Order the MRI now. The combination of acute traumatic mechanism (heavy squat), severe pain limiting function, and normal radiographs is the classic presentation for radiographically occult avulsion injury 2, 5, 3.