At the S1 level, which muscle is 3/5?

At the S1 level, which muscle is 3/5?

• A. Hip abductors
• B. Hip extensors
• C. Plantar flexors
• D. Abdominals

Answer: (A)

Movement against gravity with no added resistance is what defines a grade of three in manual muscle testing. At the S1 level, the hip abductors are the group most commonly showing this grade because they are innervated by nerves that include the S1 contribution (gluteus medius and gluteus minimus via the superior gluteal nerve). When S1-related weakness is present, these proximal muscles aren’t strong enough to sustain resistance, so the patient can still abduct the hip through its full range against gravity but cannot hold or push against an examiner’s force. Clinically, you’d see the pelvis tend to drop on the opposite side when testing hip abduction with a single-leg stance or when attempting to resist abduction, reflecting a 3/5 strength. To test, have the patient abduct the thigh against gravity and then apply gentle resistance; if movement occurs through full ROM but falters with resistance, the grade is three. Other muscles listed are tied to different nerve roots or functions, so their strength grades would align with different patterns of weakness unless more extensive S1 involvement is present.

Movement against gravity with no added resistance is what defines a grade of three in manual muscle testing. At the S1 level, the hip abductors are the group most commonly showing this grade because they are innervated by nerves that include the S1 contribution (gluteus medius and gluteus minimus via the superior gluteal nerve). When S1-related weakness is present, these proximal muscles aren’t strong enough to sustain resistance, so the patient can still abduct the hip through its full range against gravity but cannot hold or push against an examiner’s force. Clinically, you’d see the pelvis tend to drop on the opposite side when testing hip abduction with a single-leg stance or when attempting to resist abduction, reflecting a 3/5 strength. To test, have the patient abduct the thigh against gravity and then apply gentle resistance; if movement occurs through full ROM but falters with resistance, the grade is three. Other muscles listed are tied to different nerve roots or functions, so their strength grades would align with different patterns of weakness unless more extensive S1 involvement is present.