followed by non-weight-bearing exercise and physiotherapy over six to twelve months or more. REFERRALS Refer to physiotherapist for planning of a six to twelve months' return programme back to sport. Refer to orthopaedic surgeon for arthroscopic treatment.
EXERCISE PRESCRIPTION No or low impact is allowed over the first months to avoid turning a lower grade OCD into a higher. Cycling and water exercises are good alternatives to keep up general fitness.
Normal clinical symptoms and signs and use repetitive X-rays, MRI and arthroscopy. Routine MRI may well show good healing and no bone oedema, whereas anthroscopy demonstrates that the fibrocartilage is soft and does not hold for impact. Cartilage-specific sequences on MRI are under development to improve this accuracy. DIFFERENTIAL DIAGNOSES Meniscal tear (locking and effusion after sprain), osteochondral fracture or chondral injury (acute onset after direct trauma).
PROGNOSIS Unpredictable but many of these injuries respond well to micro-fracture. Since the injury usually takes a very long time to heal, many young professional players' careers are ended.
SYMPTOMS The knee gives way (often with a loud popping sound) followed by immediate haemarthro-sis and pain in the anterior part of the knee, preventing further activity. AETIOLOGY The medial patella retinaculum ruptures, allowing the kneecap to migrate laterally. The kneecap can lock the knee in the flexed position by getting stuck outside the lateral femur condyle. The patella dislocates during a valgus hyper-extension sprain or from direct side trauma. The first time this happens the diagnosis is clear unless there is a spontaneous reduction. In many cases it is however a non-contact injury where the player loses their balance and twists the knee. This injury is often associated with other injuries to cartilage, menisci, capsule or ligaments.
CLINICAL FINDINGS There is intra-articular bleeding (haemarthrosis) in most cases. In first dislocations, if there is a retinaculum rupture, blood can penetrate from the joint and cause bruising around the medial anterior part of the knee. There is distinct tenderness on palpation around the patella. Since there are often associated injuries, examination must also include tests for cruciate ligaments, menisci and cartilage. INVESTIGATIONS Clinical examination is the most important tool for diagnosis and should include tests for all ligaments and other structures in the knee. X-ray is valuable to rule out fractures, in particular in growing or elderly athletes. MRI or arthroscopy is important for evaluating associated injuries. Note! There is a high risk that the cartilage on the kneecap as well as on the femur condyle will have been damaged. The combination of ACL rupture and patella dislocation is also not uncommon. TREATMENT A dislocated kneecap can be reposi-tioned by gently extending the knee with the foot externally rotated to allow the kneecap to slide back into position. An athlete with haemarthrosis and suspected patella dislocation should be seen by an orthopaedic surgeon to consider early arthroscopy. This procedure can verify the diagnosis and deal with associated injuries that are often missed. Surgical repair of the medial retinaculum is only indicated in severe cases. If the injury reoccurs despite thorough physiotherapy other surgical options are available. These cases should be handled by a knee specialist. REFERRALS Refer to an orthopaedic surgeon for further investigations to verify the extent of the injury. Physiotherapists will be involved in close collaboration with the surgeon.
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