Recurrent Knee Pain

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

  • Haemochromatosis
  • Recurrent Haemarthroses (e.g. Coagulation Disorder)
  • Osteosarcoma

Ready Reckoner

Key distinguishing features of the most common diagnoses

Ligament Sprain/ Soft TissueOsteoarthritis Cartilage InjuryChondromalacia Patellae/Patellofemoral PainOsgood– Schlatter’s
Specific InjuryYesNoYesNoNo
Both Knees AffectedNoPossibleNoPossiblePossible
More Common in WomenNoNoNoYesNo

Possible Investigations


Possible:FBC, CRP, uric acid, MRI, autoantibodies.

Small Print:HLA-B27, joint aspiration, hip or back investigations if referred pain suspected, alkaline phosphatase, serum ferritin, coagulation screen.

  • X-ray: May give clues to many of the possible causes, or confirmatory evidence when clinical suspicion is high – for example, with osteoarthritis, bony loose body, Paget’s, osteochondritis dissecans.
  • FBC, CRP: CRP elevated and Hb may be reduced in inflammatory polyarthritis.
  • Uric acid: Typically elevated in gout.
  • MRI: Useful to assess soft tissue such as cartilage, especially if surgery is being considered.
  • Autoantibodies: If inflammatory polyarthritis suspected.
  • HLA-B27: A high prevalence in spondoarthritides.
  • Joint aspiration: May be diagnostically useful if an effusion is present – for example, revealing positively birefringent crystals in pseudogout. In practice, usually performed after specialist referral.
  • Hip or back investigations: Appropriate radiology may be necessary if it is thought the knee pain is referred from these areas.
  • Alkaline phosphatase: Elevated in Paget’s.
  • Serum ferritin: Elevated in haemochromatosis.
  • Coagulation screen: If coagulopathy suspected.

Top Tips

  • Patients place great value on X-rays whereas, in practice, they may contribute little to management of straightforward recurrent knee pain. To prevent an unsatisfactory outcome, consider proactively broaching the fact that an X-ray may be unnecessary.
  • Insisting that the patient accurately localises the pain – if possible – may usefully limit the diagnostic possibilities.
  • ‘Straightforward’ osteoarthritis can become quite suddenly more painful, often for no obvious reason – exacerbations and remissions are part of the natural history of the disease.
  • Keen sports people often present with recurrent knee pain and are unlikely to indulge in the GP’s time-honoured ‘wait and see’ approach. Earlier investigation or intervention may prove necessary.

Red Flags

  • Do not forget that knee pain may be referred – if the cause isn’t immediately apparent, examine the hip, especially in children.
  • Anterior cruciate ligament injury is quite easily missed in casualty in the acute stage. It may only present later with an unstable knee.
  • Osteosarcomas are rare: But most commonly occur near the knee. Beware of unexplained constant, increasing pain waking the patient at night. Swelling and inflammation will only appear later.

Published: 2nd August 2022 Updated: 10th April 2024

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