If there is atrophy in the infraspinous fossa with weak, pain-free abduction, which tissue involvement is most likely?

If there is atrophy in the infraspinous fossa with weak, pain-free abduction, which tissue involvement is most likely?

• A. Accessory movement involvement
• B. Contractile tissue involvement
• C. Inert tissue involvement
• D. Nervous tissue involvement

Answer: (D)

When a muscle shows atrophy in its region with weakness that is painless during movement, think loss of neural input to that muscle rather than a primary tear or inflammation. The infraspinatus sits in the infraspinous fossa and is innervated by the suprascapular nerve. If the nerve is impaired, the muscle undergoes neurogenic atrophy and produces weakness that can be painless, because the issue lies in nerve supply rather than the muscle or joint surfaces themselves. This fits nervous tissue involvement. In contrast, contractile tissue involvement typically causes pain with resisted contraction and tenderness in the muscle; inert tissue involvement (such as joint capsule or ligaments) tends to produce pain with movement or mechanical symptoms rather than focal muscle atrophy; and accessory movement issues relate to joint play rather than the neural supply to a muscle.

When a muscle shows atrophy in its region with weakness that is painless during movement, think loss of neural input to that muscle rather than a primary tear or inflammation. The infraspinatus sits in the infraspinous fossa and is innervated by the suprascapular nerve. If the nerve is impaired, the muscle undergoes neurogenic atrophy and produces weakness that can be painless, because the issue lies in nerve supply rather than the muscle or joint surfaces themselves. This fits nervous tissue involvement. In contrast, contractile tissue involvement typically causes pain with resisted contraction and tenderness in the muscle; inert tissue involvement (such as joint capsule or ligaments) tends to produce pain with movement or mechanical symptoms rather than focal muscle atrophy; and accessory movement issues relate to joint play rather than the neural supply to a muscle.