History and exam

Key diagnostic factors

common

characteristic posturing of joint

Anterior shoulder dislocations present with the arm in a characteristic position of external rotation and slight abduction. Posterior shoulder dislocations are rare and present with the arm held in adduction and internal rotation; the shoulder cannot be externally rotated, either actively or passively. Inferior shoulder dislocations present with the arm fully abducted and elbow commonly flexed on or behind the head.[21][22][54]

Patellar dislocation often presents with a swollen knee held in flexion with an obvious lateral prominence.

Elbow dislocation typically presents with the elbow held in flexion.

The classic appearance of posterior hip dislocation is with the hip in a position of flexion, internal rotation, and adduction. With anterior hip dislocations, the hip is classically held in external rotation, with mild flexion and abduction.[4]

pain

Typically, patients have significant pain on movement and are very apprehensive about motion of the affected joint.

inability to move joint

Patients are usually unable to move the joint or have incomplete range of motion.

tenderness

Patients have tenderness around the dislocated joint.

swelling

Patients often present with varying degrees of edema around the dislocated joint.

sciatic nerve injury with hip dislocation

May occur with stretching of the nerve over the posteriorly dislocated femoral head. Fragments of bone from a posterior wall fracture can also cause injury to the nerve.[4]

injury to the femoral artery, vein, or nerve with hip dislocation

Anterior hip dislocation can cause injury to the femoral artery, vein, or nerve.

concomitant injury with hip dislocation

Concomitant injuries are quite common with hip dislocations. Ipsilateral knee, patella, and femur fractures are common. Pelvic fractures and spine injuries may also be seen.[4]

cruciate ligament injury with patellar dislocation

May accompany patellar dislocation.

If pain permits, the physician should perform a full knee exam to determine concomitant injury to other ligamentous structures (e.g., anterior/posterior drawer and Lachman tests to examine cruciate ligaments).

meniscal tears with patellar dislocation

May accompany patellar or knee dislocation.

McMurray test can be used to evaluate for meniscal tears in patients with patellar dislocation.

ligamentous injuries of the knee with patellar dislocation

May accompany patellar or knee dislocation.

Varus and valgus stress testing can be used to evaluate the function of various knee ligaments.

patellar or quadriceps tendon rupture with patellar dislocation

May accompany patellar or knee dislocation.

The patient should demonstrate the ability to perform a supine straight leg raise to exclude rupture of these structures.[16][32][56][57]

Other diagnostic factors

common

ecchymosis with finger dislocation

Finger dislocations may be accompanied by ecchymosis (bruising).

uncommon

hemarthrosis with patellar dislocation

Bleeding into joint spaces may occur with patellar dislocation.

Risk factors

strong

sports-related activities

Most common cause of shoulder, finger, patella, and elbow dislocations.[5][7][10][14][18][33]

motor vehicle accident (hip dislocation)

Axial loading of the femur toward the acetabulum is the classically described mechanism for hip dislocation. It is commonly observed with impact of the bent knee with a dashboard in a motor vehicle accident.[36]

ligamentous laxity

Those with loose ligaments may experience sprains or dislocations more frequently.

Loose ligaments may be generalized or confined to a few joints; the trait is usually hereditary. Affected patients have joints with a wide range of movement (e.g., "double-jointed" people).

Ehlers-Danlos syndrome

May be the cause of widespread laxity of connective tissue. This is a rare inherited condition characterized by unusually flexible joints, very elastic skin, and fragile tissues.

males between adolescence and 30 years of age

Shoulder and finger injuries occur most commonly in this patient group following injuries on the sports field.[7][8][10]

women ages 61-80 years (shoulder dislocation)

Incidence rates for shoulder dislocation are high in this patient group.[5][7][8]

prior history of joint instability

Patients with a previous shoulder or patellar dislocation are more prone to redislocation.

skeletal or muscular dysplasia

Causes patellar laxity as a result of hypermobility or lack of medial restraints and appears to be the most significant contributor to instability of the patellofemoral joint.[16][31][32]

external tibial torsion (patellar dislocation)

Refers to a tibia that rotates outward and is associated with over-pronated feet and patellar injuries.[30]

patella alta (patellar dislocation)

Refers to an abnormally high patella in relation to the femur. It may result in dislocation of the patella.[26][28][29]

weak

high Q angle (patellar dislocation)

A measurement of the angle between the quadriceps and the patellar tendon. It provides useful information about the alignment of the knee joint, which, if outside normal ranges, can be a precursor for overuse injuries such as dislocation.[27]

A high Q angle often results in maltracking of the patella (i.e., it does not travel over the front of the knee joint as it should).

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