Emergency Medicine

306 Orthopaedic Emergencies

INJURIES TO THE LOWER FEMUR, KNEE AND UPPER TIBIA

3 Aspirate a tense haemarthrosis first, before applying the plaster cylinder (see

p. 492).

Dislocation of the patella

DIAGNOSIS

1 The patella usually dislocates laterally in teenage girls and may become

recurrent. It is most commonly associated with a direct blow to the anterior

or medial surface of the patella.

2 Patients complain of the knee suddenly giving way, and inability to weight-

bear or extend the knee and are often in considerable pain.

3 Examine for an anterior defect, a laterally deviated patella, and swelling and

media l joint line tenderness of t he part ly f lexed k nee.

4 Sometimes, spontaneous reduction occurs and the patient then presents

with a tender knee, particularly along the medial border of the patella.

(i) A careful history and a positive ‘patella apprehension’ test (moving

the patella laterally causes pain) suggest the original injury.

MANAGEMENT

1 Reduce under nitrous oxide with oxygen (Entonox™) analgesia by pushing

the patella medially with firm pressure, while extending the knee.

2 Request a skyline patellar X-ray after the reduction to exclude an associated

osteochondral fracture.

3 Place the leg in a padded plaster cylinder and refer the patient to the next

fracture clinic.

4 Use a pressure bandage instead of a plaster cylinder if the dislocation is

recurrent.

Soft-tissue injuries of the knee

A careful history of the mechanism of injury and the subsequent events is essen-

tial, as knee examination is often difficult or impossible immediately afterwards

due to acute pain. Always lie the patient on an examination trolley properly

undressed.

DIAGNOSIS

1 Rapid swelling of the knee suggests a haemarthrosis, usually due to an

anterior cruciate tear, peripheral meniscal tear, or intra-articular fracture.

(i) Delayed swelling, occurring after several hours, is more likely to

be due to a serous effusion.

2 Injuries may be deduced from the direction of force.

(i) Sideways stresses will rupture the collateral ligaments or joint

capsule.