Impingement syndrome is a painful encroachment of joint motion caused by protruding bony or soft tissue structures.

Epidemiology

Impingement syndromes are common and can occur at any age.

Risk factors

• developmental osseous anomalies

• overuse activity

• trauma

Associations

• osteoarthritis

• tendinosis and tears

• myotendinous injury

• bursitis

• chondral and labral injury

Clinical presentation

The usual presentation of impingement syndrome is a painful reduction in the range of motion of the affected joint ¹.

Pathology

The pathological correlate of impingement is a mechanical entrapment or encroachment of soft tissue structures between bony formations of a joint.

Aetiology

Bony structural abnormalities due to:

• developmental anomalies

• trauma

• repetitive microtrauma/overuse

• malunion

• osteoarthritis

Location

Typical locations are the following joints ¹:

• shoulder

• hip

• ankle

• wrist

• knee

Classification

Internal impingement: refers to an intraarticular impingement, the affected structures are within the joint e.g. femoroacetabular impingement, anterior, anteromedial, anterolateral, posterior or posteromedial ankle impingement, subcoracoid impingement

External impingement: refers to an extra-articular impingement, of which the affected structures lie outside the joint e.g. ischiofemoral impingement, extra-articular lateral hindfoot impingement

Radiographic features

Plain radiograph/CT

Depiction of predisposing osseous abnormalities e.g.:

• os acromiale, acromion type III, decreased coracohumeral distance

• cam and/or pincer morphology,  decreased ischiofemoral distance

• ulnar variance

• anterior/anteromedial tibiotalar osteophytes, flat foot, hindfoot valgus

Ultrasound

A dynamic ultrasound examination allows the demonstration of the abutment or narrowing effect on the impinged soft tissue structures ¹.

MRI

In addition to osseous morphologies or abnormalities, MRI can depict a stress response of the affected bony and soft tissue structures as e.g. bone marrow-like signal of the affected bone or signs of tendinosis, muscle oedema or tears of the encroached tendinous and/or myotendinous structures ¹.  Furthermore, it can show sequelae as ligamentous injuries, bursitis, capsulitis, chondral or labral injury and muscular changes such as atrophy or fatty degeneration.  

Treatment and prognosis

Treatment depends on the location and extent of symptoms. It typically includes exercise therapy, activity modification, taping, physical and manual therapy, temporary immobilisation as well as nonsteroidal anti-inflammatory drugs, and guided injections of local anaesthetic or corticosteroids. Surgery is usually performed if conservative management fails or if complications have already occurred.

See also

• shoulder impingement

• hip impingement

• ankle impingement syndromes

• ulnar-sided wrist impaction and impingement syndromes