How do you differentiate between hamstring contracture and gastrocnemius contracture in a patient with cerebral palsy?

Differentiating Hamstring Contracture from Gastrocnemius Contracture

To differentiate hamstring contracture from gastrocnemius contracture in cerebral palsy, perform the popliteal angle test with the hip at 90° flexion (which isolates the hamstrings) and the Silverskiöld test with the knee extended versus flexed (which isolates the gastrocnemius).

Clinical Examination Technique

Hamstring Contracture Assessment

• Measure the popliteal angle by flexing the hip to 90° and then extending the knee as far as possible while keeping the hip flexed 1
• A popliteal angle greater than 50° indicates abnormal hamstring tightness in children aged 1 year and older 1
• Between ages 1-3 years, the normal mean angle is 6° (range 0-15°); at age 4, it rises to 17° in girls and 27° in boys; and at ≥5 years, the mean is 26° (range 0-50°) 1
• The key principle: Hip flexion at 90° eliminates the contribution of the gastrocnemius (which does not cross the hip joint), isolating hamstring tightness 2

Gastrocnemius Contracture Assessment

• Perform the Silverskiöld test by measuring ankle dorsiflexion with the knee extended and then with the knee flexed to 90° 2
• If dorsiflexion improves significantly with knee flexion, this indicates isolated gastrocnemius contracture (since the gastrocnemius crosses both the knee and ankle joints) 2
• If dorsiflexion remains limited regardless of knee position, this suggests soleus or combined triceps surae contracture 3
• The key principle: Knee flexion relaxes the gastrocnemius but not the soleus, allowing differentiation between these two components of the triceps surae 3

Systematic Assessment Approach

Range of Motion Testing Using Goniometry

• Use standardized goniometry to measure joint angles at the hip, knee, and ankle joints 2
• Assess both lower extremities including the iliotibial band, hamstrings, and gastrocnemius as part of baseline evaluation 2
• Perform these measurements every 6 months in ambulatory patients to identify emerging muscle hypoextensibility and joint contractures 2

Velocity-Dependent Testing Considerations

• During passive stretch testing, contracture (non-neural component) manifests as increased resistance at slow stretch speeds, while spasticity (neural component) shows velocity-dependent resistance that increases with faster stretches 4, 5
• Contracture reflects altered passive muscle stiffness, whereas spasticity involves exaggerated stretch reflexes 4, 5
• Both components often coexist in cerebral palsy, requiring assessment at multiple speeds to differentiate their relative contributions 4

Common Pitfalls to Avoid

• Do not assess hamstrings with the hip in neutral position, as this allows the gastrocnemius to contribute to knee extension limitation, confounding the assessment 1
• Do not assume a single muscle group is responsible for limited motion—combined hamstring and gastrocnemius contractures frequently coexist in cerebral palsy 2, 6
• Do not rely on a single assessment timepoint—contractures evolve over time and require serial monitoring every 4-6 months to guide therapeutic interventions 2
• Remember that motor types and tone evolve during the first 2 years of life, so repeated assessments are essential 7

Clinical Implications for Management

• Identifying the specific contracted muscle group determines whether surgical intervention should target hamstring lengthening, gastrocnemius-soleus recession, or combined procedures 3
• Accurate differentiation guides appropriate orthotic prescription and physical therapy targeting 2
• Early identification of emerging contractures allows timely intervention to prevent functional deterioration and secondary musculoskeletal complications 2, 8