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Probability diagnosis

Ligament strains and sprains ± traumatic synovitis


Patellofemoral syndrome

Prepatellar bursitis

Serious disorders not to be missed

Vascular disorders:

  • deep venous thrombosis

  • superficial thrombophlebitis


  • primary in bone

  • metastases


  • septic arthritis

  • tuberculosis

Rheumatic fever

Rheumatoid arthritis

Acute cruciate ligament tear

Juvenile chronic arthritis

Pitfalls (often missed)

Referred pain: back or hip disease

Foreign bodies

Intra-articular loose bodies

Osteochondritis dissecans


Synovial chondromatosis

Osgood–Schlatter disorder

Meniscal tears

Fractures around knee

Pseudogout (chondrocalcinosis)

Gout → patellar bursitis

Ruptured popliteal (Baker’s) cyst


  • sarcoidosis

  • Paget disease

  • spondyloarthropathy

Masquerades checklist



Spinal dysfunction (referred)

Is the patient trying to tell me something?

Psychogenic factors relevant, especially with possible injury compensation.

Key history

The history helps diagnosis, especially evaluating the nature of the injury. Define whether the pain is acute or chronic, dull or sharp, continuous or recurring. Keep in mind age-related causes and past history.

Key examination

The provisional diagnosis may be evident from a combination of the history and simple inspection of the joint but the process of testing palpation, movements (active and passive) and specific structures of the knee joint helps pinpoint the disorder.

Key investigations



  • connective tissue antibodies

  • blood culture

  • plain X-ray including special views

  • bone scan

  • ultrasound

  • arthrography: CT scan, MRI (excellent for investigating internal ‘derangement’)

  • arthroscopy

  • aspiration of fluid for culture or crystal examination.

Diagnostic tips

Examine the hip and lumbosacral spine if examination of the knee is normal but knee pain is the complaint.

Acute haemarthrosis following an injury should be regarded as an anterior cruciate ligament tear until proved otherwise.

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