The people in this column are fictional cases composed from a range of situations, not real individuals. Any individual's condition requires direct assessment by a professional.

Three people say their shoulder hurts. An office worker in his 40s gets a sharp twinge only around shoulder height when he raises his arm out to the side. A homemaker in her 50s can't tie her hair back or reach behind her back. A man in his 60s can't lift his arm at all since he fell. They all say the same words: "My shoulder hurts." But those three sentences point to different conditions, and each calls for something different.

Mr. A: a twinge only at shoulder height

Mr. A, a 45-year-old office worker, has felt his shoulder catch every time he reaches for a file box on a high shelf over the past few weeks. When he slowly raises his arm out to the side, it's fine at first. Around shoulder height it twinges, but once he gets past that range and lifts higher, it actually hurts less. Sleeping on that side is uncomfortable, too.

Pain that appears only at certain angles like this is called a "painful arc." The exact range varies slightly by source. Physical therapy resources give 60 to 120 degrees of arm elevation to the side, while a review in American Family Physician gives 60 to 100 degrees. The usual explanation is that in this range, the rotator cuff tendons and bursa passing under the acromion, the bony tip at the top of the shoulder, get irritated.

This used to be called "impingement syndrome." Today the term "rotator cuff related shoulder pain" is more common. The change reflects the view that the simple picture of bone pressing on tendon doesn't fully explain it.

One more thing stands out in Mr. A's pattern. When someone else lifts his arm for him, it goes up almost all the way. That means the path of movement itself is open. On the other hand, if it hurt only when the arm was raised nearly all the way (170 to 180 degrees), the acromioclavicular joint at the tip of the shoulder would be considered separately. A painful arc alone doesn't determine a diagnosis. It's just a clue, interpreted together with other tests.

• Pain gets worse around shoulder height when raising the arm to the side
• Pain eases when the arm goes past that range
• Overhead movements, like taking things off a high shelf, are uncomfortable
• Lying on the painful side is uncomfortable
• The arm goes up fairly far when someone else lifts it

Ms. B: an arm that won't go up in any direction

Ms. B, 53, was diagnosed with diabetes a few years ago. At some point it became hard to tie her hair back, and when she reaches behind her back to fasten her bra, her arm gets stuck. It isn't just one angle that hurts. Reaching forward, reaching to the side, and rotating the arm outward have all become shorter. Some nights a throbbing ache wakes her up.

Here's the key difference from Mr. A: even when a family member lifts her arm, it doesn't go up much. This is the pattern seen in adhesive capsulitis, commonly called frozen shoulder, where the capsule surrounding the joint becomes thick and stiff. Rotating the arm outward is often especially limited.

According to a review in American Family Physician, frozen shoulder affects 2–5% of the general population and is most common in women aged 40 to 60. In a meta-analysis cited in the same review, people with diabetes were about 5 times more likely to develop it than controls. An association with hypothyroidism has also been reported. Ms. B's age and medical history both fit this picture.

Mr. C: can't lift his arm after a fall

Mr. C, 64, slipped on the stairs and caught himself with his hand. Since that day, he has had trouble lifting his arm on his own. The lack of strength bothers him more than the pain. When someone raises his arm high and lets go, he can't lower it slowly; it just drops.

This case calls for a different order than the first two. Before looking up exercise videos at home, he should see an orthopedic specialist first. Shoulder pain and weakness that start after a fall or a blow after age 40 need to be checked first for a possible rotator cuff tear. Whether imaging is needed and which treatment fits is for the specialist to decide.

One more point: seeing a tear on imaging doesn't always mean that's what's causing the pain. The same review cites a study in which MRI found partial or full-thickness tears in 54% of people over 60 who had no symptoms. That's why imaging results are read together with symptoms and examination findings. When strength is lost after a clear event, as with Mr. C, the key is not to put off that check.

Four questions that separate the three

Put the three side by side and the dividing lines become clear. At what angle does it hurt? Does the arm go up when someone else lifts it? Is strength still there? Was there a triggering event? Pain only in the middle range with the arm going up when lifted points toward Mr. A; all directions blocked together points toward Ms. B; strength lost after an injury points toward Mr. C. Of course, real shoulders often don't divide this neatly.

From a chiropractic perspective, the first step is to compare how far you can raise your arm yourself with how far it goes when the examiner lifts it. Next come the Hawkins and Neer tests for pain from irritation under the acromion, the empty can test, holding against resistance with the thumb pointing down, for supraspinatus function, and the drop arm test for the possibility of a large tear. On top of that, we check whether the shoulder blade moves well with the arm and whether the upper back is stiff. If the arm is numb or pain runs below the elbow, the problem may be coming from the neck, so the neck is assessed as well.

The approach to management differs too. For rotator cuff related pain like Mr. A's, you cut back on lifting heavy things overhead for a while, but you don't stop using the shoulder altogether. Resistance exercise is recommended as first-line management, starting light and progressing gradually. Research hasn't settled how much pain to allow during exercise, so it's adjusted based on how you respond.

For a frozen shoulder pattern like Ms. B's, there is reported evidence that joint mobilization (a hands-on technique that gently moves the joint) combined with exercise improves movement and function. Recovery speed varies a lot from person to person. If there's little change after several months of management, the next step is to get a specialist's opinion on whether injections or other treatments are needed.

See a doctor first if…

• Sudden arm weakness after a fall or a blow
• Being almost unable to lift the arm on your own
• No improvement, or steady worsening, after several weeks of management
• A red, hot, swollen shoulder, or severe night pain with fever
• Unexplained weight loss, night sweats, or general weakness occurring along with it
• Arm numbness, or pain spreading below the elbow

If any of these apply, see an orthopedic specialist first. Whether imaging, medication, procedures, or surgery are needed is for the specialist to decide.

Stand in front of a mirror and slowly raise your arm out to the side. Note the angle where the pain starts and where it eases. Written down, that becomes the most useful information you can bring to an appointment.

This article is for general health information. Everyone's condition is different, so an accurate assessment requires consulting a professional.