Infraspinatus & Teres Minor: the quiet stabilisers that modern life keeps irritating

Dear reader,

If shoulders could talk, most of them wouldn’t complain about the big muscles. They’d complain about the small ones doing unpaid overtime.

Two of the most overworked (and under-appreciated) are infraspinatus and teres minor — the back-of-shoulder rotator cuff pair whose main job is to keep the humeral head behaving like a well-trained guest in the shoulder socket: centred, calm, and not crashing the party.

What they actually do (in human terms)

• They externally rotate the shoulder (turn your arm out).

• More importantly, they stabilise the shoulder joint during movement — especially when your arm lifts, reaches, presses, throws, or hangs.

• They act like precision steering + brakes. Big muscles create force; these two keep the joint “on track”.

When they’re irritated, the shoulder often feels mysteriously unstable, pinchy, weak, or naggy — even if scans look “fine”.

Interesting anatomical facts (the nerdy bits, kept friendly)

• Infraspinatus is the larger external rotator and blends closely with the posterior shoulder capsule — meaning capsular stiffness and infraspinatus tension often travel together.

• Teres minor is smaller but strategically placed; it helps control the humeral head especially when the arm is slightly abducted (away from your body). It’s also a neighbour of the quadrilateral space, where the axillary nerve passes — one reason some people feel strange “deep posterior shoulder” or outer-arm sensations when it’s grumpy.

• Referral patterns can be misleading:

  • Infraspinatus can refer pain to the front of the shoulder and down the arm — people swear it’s biceps or “impingement”.

  • Teres minor often refers to the back/outside shoulder (posterior deltoid area), sometimes feeling like a stubborn “knot that never leaves”.

So yes — the pain can show up somewhere else, which is why shoulders love confusing good people.

Why modern life targets them so often

Modern shoulders live in a world of internal rotation:

• phones, laptops, steering wheels

• slumped thoracic spine

• rounded shoulders, head forward

• elbows glued to the body while hands live in front of the chest

In that posture, the shoulder tends to sit slightly forward in the socket. Your brain then hires infraspinatus and teres minor to pull the head of the humerus back and keep it centred… for hours.

Then, after a day of that, you go to the gym and do:

• bench press

• push-ups

• dips

• shoulder press

  
  

  (usually far more pushing than pulling)

Now the same small stabilisers must also control the joint under load — especially during the lowering phase (eccentric control), where many modern shoulder flare-ups begin.

That’s the mismatch:

we underuse external rotation all day, then demand stability under high force later.

The main causes I see behind the scenes

In JANMI terms, it’s rarely “one muscle gone wrong”. It’s usually a pattern:

1. Scapula that doesn’t set well

   • If the shoulder blade isn’t stable (often from fatigue in mid/lower traps or serratus), the rotator cuff works harder to keep the ball centred.

2. Thoracic stiffness

   • A stiff upper back reduces clean overhead mechanics. The cuff becomes the compensator.

3. Overdominant front-body tone

   • Pec and anterior shoulder structures tighten; the posterior cuff becomes the counter-force.

4. Repetitive reaching in front

   • Keyboard, phone, cooking, childcare, tools — lots of “life in front of the body”.

5. Overhead or throwing work

   • The cuff is a deceleration system. Deceleration is where tissues complain.

6. Sleep positions

   • Side-sleeping with the shoulder rolled forward can keep these tissues on a low simmer all night.

How this shows up as “modern shoulder pain”

People don’t walk in saying, “Hello Paulius, my infraspinatus is upset.”

They say things like:

• “It pinches when I reach up.”

• “It’s sore in the front but I can’t find where it comes from.”

• “External rotation feels blocked or sharp.”

• “It aches after desk work.”

• “It feels unstable when I press or lift.”

• “It’s worst at night or after training.”

Often, the felt problem is the front of the shoulder — but the quiet driver is posterior cuff overload plus poor centring.

The JANMI angle: precision beats force

These muscles don’t respond well to aggression. They respond well to clarity:

• clear assessment of movement pattern

• calm, specific soft tissue work

• restoring shoulder blade rhythm

• teaching the nervous system that the joint is safe again

Not dramatic. Just intelligent.

If your shoulder pain is persistent, sharp, worsening, or includes numbness/weakness — get assessed by a qualified professional. But if it’s that classic modern ache/pinch/blocked rotation story, don’t ignore the back-of-shoulder stabilisers. They’re often the hidden staff keeping the whole building standing.

Until next time,

Paulius