Causes of knee pain


Acute knee injury

  • Knee cartilage injuries: medial or meniscal injury.
  • Knee ligament injuries: medial collateral ligament (MCL), lateral collateral ligament (LCL), posterior cruciate ligament (PCL), anterior cruciate ligament (ACL).
  • Leg fractures and dislocations: knee fractures and dislocations, distal femoral fractures, proximal tibial and fibular fractures.
  • Patellar tendon rupture.

Global knee pain

  • Monoarthritis.
  • Polyarthritis: osteoarthritis, rheumatoid arthritis.
  • Crystal arthropathies: gout, pseudogout.
  • Seronegative arthropathies, eg ankylosing spondylitis, Reiter's syndrome, enteropathic arthritis, psoriatic arthritis, Behçet's disease, juvenile idiopathic arthritis.
  • Infective causes: septic arthritis, osteomyelitis.
  • Disease of bone around the knee: osteosarcoma: usually affects children. The most common sites are around the knee or proximal humerus. The most frequent presenting symptom of osteosarcoma is pain, especially with activity.[1] See separate article Bone Tumours.
  • Referred pain (usually from the hip).
  • Rare causes, eg haemochromatosis, rheumatic fever, spontaneous haemarthrosis (may occur in coagulation disorders, especially haemophilia), familial Mediterranean fever.

Anterior knee pain

Common causes include:

  • Patellofemoral pain syndrome (also known as chondromalacia patellae).
  • Fat pad impingement: the infrapatellar fat pad is impinged between the patella and the femoral condyle due to a direct blow to the knee. Treatment includes patellar taping to relieve impingement.
  • Patellofemoral instability (or recurrent patellar subluxation): this is more common in females - patellar hypermobility with apprehension and pain when the patella is pushed laterally are found on examination. Treatment can include bracing and crutches to reduce weight-bearing. Exercises to strengthen the vastus medialis obliquus are needed. Surgery may be required if conservative management fails.

Other causes include:

  • Referred pain from the hip, eg slipped upper (capital) femoral epiphysis, Perthes' disease.
  • Osteochondritis dissecans.
  • Bone tumour.
  • Prepatellar bursitis or infrapatellar bursitis.
  • Patellar stress fracture.
  • Osgood-Schlatter disease.
  • Sinding-Larsen Johansson disease.

Lateral knee pain

Common causes include:

  • Iliotibial band friction syndrome: this occurs due to friction between the iliotibial band and the underlying lateral epicondyle of the femur. It produces lateral knee pain in cyclists, dancers, long-distance runners, football players, and military recruits. There is tenderness over the lateral epicondyle of the femur 1-2 cm above the lateral joint line. Flexion/extension of the knee can reproduce symptoms. It is more likely with poor muscles, lax ligaments and poor training regimes. Treatment includes non-steroidal anti-inflammatory drugs (NSAIDs), massage, stretching, muscle strengthening and correction of predisposing factors (eg it is more common in downhill running). Steroid injection and surgery are rarely needed.
  • Lateral meniscus problem (tear, degeneration, cyst).

Other causes include: common peroneal nerve injury, patellofemoral syndrome, osteoarthritis, referred pain from the hip or the lumbar spine.

Medial knee pain

Common causes include:

  • Patellofemoral syndrome (see 'Anterior knee pain', above).
  • Medial meniscus problem (tear, degeneration, cyst).

Other causes include: tumour, referred pain from the hip or the lumbar spine, MCL injury, osteoarthritis.

Posterior knee pain

Common causes include:

  • Knee joint effusion.
  • Referred pain from the lumbar spine or patellofemoral joint.

Other causes include: Baker's cyst, deep vein thrombosis, peripheral vascular disease, PCL injury.