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Key facts and checkpoints
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A ruptured anterior cruciate ligament (ACL) is the most commonly missed injury of the knee.
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A rapid onset of painful knee swelling (mins to 1–4 h) after injury indicates blood in the joint—haemarthrosis: the main causes are torn cruciate ligaments, capsular tears with collateral ligament tears, peripheral meniscal tears, fractures and dislocations.
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Swelling over 1–2 days after injury indicates synovial fluid—traumatic synovitis.
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Acute spontaneous inflammation of the knee may be part of a systemic condition such as rheumatoid arthritis, rheumatic fever, gout, pseudogout (chondrocalcinosis), a spondyloarthropathy (psoriasis, ankylosing spondylitis, Reiter syndrome, bowel inflammation), Lyme disease and sarcoidosis.
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Consider Osgood-Schlatter disorder in the prepubertal child (esp. boys 10–14) presenting with knee pain.
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Disorders of the lumbosacral spine (esp. L3–S1 nerve root problems) and of the hip joint (L3 innervation) refer pain to the region of the knee joint.
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Osteoarthritis of the hip often presents as knee pain.
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Knee: diagnostic strategy model
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Probability diagnosis
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Serious disorders not to be missed
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primary in bone
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metastases
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septic arthritis
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tuberculosis
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Acute cruciate ligament tear
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Juvenile chronic arthritis
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Pitfalls (often missed)
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Referred pain: back or hip
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Foreign bodies
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Intra-articular loose bodies
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Osteochondritis dissecans
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Osteonecrosis
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Synovial chondromatosis
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Osgood–Schlatter disorder
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Meniscal tears
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Fractures around knee
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Pseudogout (chondrocalcinosis)
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Gout→patellar bursitis
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Ruptured popliteal cyst
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Rarities:
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Sarcoidosis
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Paget disease
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Spondyloarthropathy
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Osgood–Schlatter disorder
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Most common at 10–14 yrs; ♂ : ♀ = 3:1
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This is conservative as it is a self-limiting condition (6–18 mths: av. 12 mths).
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If acute, use ice packs and analgesics.
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Main approach is to abstain from or modify active sports.
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Avoid steroid injections and POP immobilisation.
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Surgery (rarely) if irritating long-term ossicle.
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Physiotherapy: gentle quadriceps stretching.
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Chondrocalcinosis of knee (pseudogout)
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Calcium pyrophosphate deposition
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In older people >60
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Can present with hot, red, swollen joint.
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Aspirate knee to search for crystals.
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Treat with NSAIDs or IA steroid injection.
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Colchicine can be used.
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Localised tenderness over joint line
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Pain on hyperextension and hyperflexion of joint
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Pain on rotation of lower leg
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Arthroscopic meniscectomy (partial or complete)
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Anterior cruciate ligament rupture
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Medial collateral ligament rupture
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Mechanism (main): direct valgus force to knee (lateral side knee) (e.g. Rugby tackle from side).
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Causes medial knee pain; aggravated by twisting. Usually responds to 6 wks in limited motion brace then knee rehabilitation.
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Patellofemoral pain syndrome
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Most common overuse injury of knee (usu. due to chondromalacia):
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Correct any underlying biomechanical abnormalities by use of orthotics and correct footwear.
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Give reassurance and supportive therapy.
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Employ quadriceps exercises with enthusiasm (very effective).
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Patellar tendonopathy (‘jumper's knee’)
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Gradual onset of anterior pain.
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Pain localised to below knee.
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Pain eased by rest, returns with activity.
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Early conservative treatment inc. rest from the offending stresses is effective. Avoid impact activity. Chronic cases invariably require surgery.
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Localised tendonopathy or bursitis
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(e.g. prepatellar bursitis, infrapatellar bursitis, biceps femoris tendonopathy, anserinus tendonopathy/bursitis)
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Generally (apart from patellar tendonopathy), the treatment is an injection of local anaesthetic and long-acting corticosteroids into and deep to the localised area of tenderness. In addition it is important to restrict the offending activity with relative rest and refer for physiotherapy for stretching exercises. Attention to biomechanical factors and footwear is important.
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Relative rest
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Weight loss
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Analgesics and/or judicious use of NSAIDs inc. COX-2 inhibitors (14–21 d)
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Consider oral glucosamine
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Walking aids and other supports
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Physiotherapy (e.g. hydrotherapy, quadriceps exercises, mobilisation and stretching techniques)
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IA injections of corticosteroids are generally not recommended but a single injection for severe pain can be very effective
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Consider intra-articular hylan G-F 20, a course of 3 injections
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Surgery: indicated for severe pain and stiffness; includes total joint replacement or hemiarthroplasty; usually excellent results