Impingement syndrome is a painful encroachment of joint motion caused by protruding bony or soft tissue structures.
Impingement syndromes are common and can occur at any age.
- developmental osseous anomalies
- overuse activity
The usual presentation of impingement syndrome is a painful reduction in the range of motion of the affected joint .
The pathological correlate of impingement is a mechanical entrapment or encroachment of soft tissue structures between bony formations of a joint.
Bony structural abnormalities due to:
- developmental anomalies
- repetitive microtrauma
Typical locations are the following joints:
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
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
A dynamic ultrasound examination allows the demonstration of the abutment or narrowing effect on the impinged soft tissue structures .
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 edema or tears of the encroached tendinous and/or myotendinous structures . Further, it can show sequelae as ligamentous injuries, bursitis, capsulitis, chondral or labral injury and muscular changes 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 immobilization as well as nonsteroidal anti-inflammatory drugs, and guided injections of local anesthetic or corticosteroids. Surgery is usually done if conservative management fails or if complications have already occurred.