Orthopaedic
CASE 76: Sporting Knee DeFormity
history
A 16-year-old girl is brought to the emergency department by ambulance complaining of leftknee pain. She has been performing gymnastics at school and remembers twisting and then developing a severe pain around her knee. Her past medical history is unremarkable. She is allergic to penicillin. Her mother reports that both the patient and her sister are ‘double-jointed’.
examination
She is holding her swollen left knee in a flexed position. There is an obvious deformity with a prominent bulge on the lateral aspect of the knee. She is very reluctant to move the knee actively. The distal neurovascular status is normal.
Questions
•What is the diagnosis?
•What manoeuvre can be performed to improve her pain and rectify the deformity?
•What should be the further management of the injury?
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100 Cases in Surgery
ANSWER 76
The patient has dislocated her patella. The injury is most common in adolescent females and in patients with joint laxity. One can also have an anatomical predisposition to dislocation: a relatively small lateral femoral condyle, genu valgum (‘knock-knees’), patella alta (high-riding patella) or quadriceps weakness.
The examination findings of a flexed swollen knee and a large bulge laterally (dislocation of the patella medially is rare) should prompt the clinician to make the diagnosis. An initial x-ray is unnecessary, as it is important to relocate the dislocated patella as soon as possible. This is achieved by getting the patient to lie supine with the hip flexed. The knee should then be passively extended while medial pressure is applied to the patella.
Following relocation, plain radiography should be performed, usually an anterior-posterior, true lateral and a skyline view of the patella. Although the injury mainly involves disruption of the medial soft tissue structures of the knee, there is a 5 per cent incidence of associated osteochondral fracture. Plain radiography also provides information as to whether there are any of the anatomical risk factors listed above.
As this is the first episode of traumatic lateral patellar dislocation, without any associated fracture, it should be treated conservatively. The knee should be immobilized in extension to allow the medial patello-femoral ligament to heal. Physiotherapy is then essential to build up the muscle strength and increase the stability of the patello-femoral joint. Unfortunately, up to 50 per cent of patients will have recurrent episodes of patello-femoral instability, which will require surgical intervention.
KEY POINTS
•patella dislocation is most common in adolescent females.
•up to 50 per cent can have recurrent symptoms requiring surgical intervention.
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Orthopaedic
CASE 77: Footballer’S Knee
history
A 34-year-old builder presents to the emergency department having injured his left knee earlier that afternoon while playing football. He describes being tackled and feeling his knee twist inwards. Immediately after the injury his knee began to swell and he was unable to continue playing. He now has only limited movement of his knee and is unable to walk.
He is otherwise fit and healthy and does not take any regular medication. He has a wife and two children and smokes 20 cigarettes a day. His average alcohol intake is 34 units a week.
examination
The left knee is held in approximately 30° of flexion. It is swollen and there is an obvious effusion. Palpation elicits localized tenderness along the medial tibio-femoral joint line. It is not possible to fully extend the knee either passively or actively. The ligamentous stability of the knee appears normal. Neurovascular examination of the limb is normal.
Questions
•What is the likely injury?
•What are the other causes of a haemarthrosis?
•How should this patient be managed?
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100 Cases in Surgery
ANSWER 77
This man has sustained a meniscal injury. Most knee injuries result in swelling which develops over hours rather than minutes. The history of immediate knee swelling suggests that there is a haemarthrosis. (This can be easily confirmed by aspirating a few millilitres of fluid from the joint using an aseptic no-touch technique.)
!Causes of a haemarthrosis
•anterior cruciate tear: in 75 per cent of cases
•meniscal tear
•Fracture
•Spontaneous haemarthrosis: haemophilia
It is not uncommon to sustain a simultaneous cruciate and meniscal injury. In practice it is often difficult to assess the ligamentous stability in the acutely injured knee and make a definitive diagnosis on clinical examination alone. However, in this case the findings of a ‘locked’ knee, and the fact there was thought to be no ligamentous deficiency, suggest an isolated meniscal injury. The classical cause of an acutely ‘locked’ knee is a ‘bucket-handle meniscal tear’. This refers to a longitudinal full-thickness tear of the meniscus. The flap that is created can flip into the joint on the other side of the femoral condyle, blocking full extension of the knee.
The blood supply of the meniscus is located at its periphery, the ‘red zone’. The inner ‘white’ portion is avascular. The importance of this relates to the location of any meniscal tear; if confined to the red zone, then there is the potential for repair and subsequent healing. In this scenario the patient should be taken to theatre for an arthroscopy. As well as allowing the knee to be ‘unlocked’, it will provide a definitive diagnosis, with the potential to repair the meniscal tear.
KEY POINTS
•a history of immediate knee swelling suggests a haemarthrosis.
•a locked knee can be caused by a bucket-handle meniscal tear.
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