Impingement
Tissue getting pinched during joint motion — whether it’s in the shoulder, hip, or spine, the principle and treatment are similar.
What it means: the basic concept
Impingement occurs when soft tissue (a tendon, bursa, or nerve) gets squeezed or pinched between bones during certain motions. The space available for that tissue narrows—either because the bones themselves have changed shape (arthritis, bone spurs), or because inflammation has swollen the tissue enough to fill the space—and when you move the joint, something gets caught.
The key feature is positional pain: it hurts in a specific arc of motion, often reproducible by the examiner with specific provocative tests. Pain that only happens when the shoulder reaches a certain height, or hip bending to a certain angle, is the impingement hallmark.
Shoulder impingement (subacromial impingement)
The shoulder is the most common site. The rotator cuff tendons and the subacromial bursa live in a tight space under the acromion (the bony roof of the shoulder). With overhead movement, these tissues can get pinched against the acromion or against bone spurs.
What happens: pain with overhead lifting or reaching, sometimes with weakness. Reaching backward (like fastening a bra) often hurts. The painful arc is typically between 60–120 degrees of elevation.
Causes: rotator cuff tendinitis, subacromial bursa inflammation, bone spurs, scapular dyskinesis (the shoulder blade moves abnormally), or a tight pec muscle pulling the head of the humerus forward.
How we diagnose it: Neer test (raising the arm overhead to squeeze the rotator cuff under the acromion), Hawkins test (bringing the arm across the body in internal rotation). MRI to look at the rotator cuff and bursa.
How we treat it: activity modification, NSAIDs, physical therapy to stretch the pec and strengthen the rotator cuff and scapular stabilizers, corticosteroid injections into the subacromial space, sometimes Tenex to the tendon if it’s degenerated.
Hip impingement (femoroacetabular impingement, or FAI)
The hip has two types of impingement. Both involve pinching of soft tissue (cartilage, labrum, or tendons) in the hip joint itself:
- Cam impingement: the femoral head is not perfectly round; a bump on the neck of the femur pinches tissue in the joint when the hip flexes and internally rotates.
- Pincer impingement: the acetabulum (socket) is too deep or angled too far inward, so the socket rim pinches tissue when the hip flexes.
What happens: pain deep in the groin or front of the hip, often triggered by sitting with the hip flexed (car driving, prolonged sitting), and by internal rotation or flexion beyond 90 degrees.
How we diagnose it: FABER test (flexion-abduction-external rotation) and FADIR test (flexion-adduction-internal rotation) reproduce pain. MRI or CT shows the anatomy.
How we treat it: activity modification, physical therapy to improve hip strength and motion, corticosteroid injections, sometimes surgical arthroscopy to trim the pinching bone or repair torn labrum if conservative care fails.
Spine nerve impingement
In the cervical (neck) or lumbar (low back) spine, a nerve root can be pinched by a bulging disc, a bone spur, or thickened ligaments, narrowing the space where the nerve exits the spine.
What happens: radiating pain, numbness, or weakness down the arm (cervical) or leg (lumbar). Pain may be worse with certain neck or back positions (extending the neck pinches more in cervical impingement; bending backward hurts in lumbar impingement).
How we diagnose it: Spurling test in the neck (extending and rotating the neck toward the painful side compresses the nerve). MRI shows the disc or spur and the nerve being compressed.
How we treat it: rest, NSAIDs, physical therapy, corticosteroid injections near the nerve (interlaminar or transforaminal epidural injection), sometimes surgery to decompress the nerve if symptoms don’t improve or if there’s progressive weakness.
How impingement is different from other joint pain
Impingement has a positional component: it hurts in specific motions and positions, not just with activity in general. A patient with shoulder impingement might have no pain lowering the arm, but severe pain lifting it overhead. This specificity is what makes impingement tests useful; reproducing the painful position often confirms the diagnosis.
In contrast, arthritis pain might hurt throughout a range of motion, and tendinopathy pain might hurt with any loaded movement of the tendon. The clinical pattern guides the diagnosis.