When It Is Not OA — Other Causes of Hip and Knee Pain

Part of The Joint Replacement Guide — Phase 1: Understanding Your Condition · Article 5 of 44 · Hip & Knee

Key Points

  • Not all hip or knee pain is caused by osteoarthritis, even in an age group in which osteoarthritis is common.
  • Pain can arise from the joint, nearby muscles or tendons, the lower back, or another medical condition.
  • Inflammatory arthritis, joint infection, osteonecrosis and fracture are among the alternative diagnoses a clinician may consider.
  • The correct diagnosis matters because investigations, treatment and the appropriate specialist can differ.
  • Most hip and knee pain is not an emergency, but sudden severe symptoms, a hot swollen joint or inability to put weight through the leg may require urgent assessment.
  • Normal blood tests or an existing diagnosis of osteoarthritis do not automatically exclude another condition.

Osteoarthritis is a common cause of persistent hip and knee pain, but it is not the only possible explanation. Some people also have more than one condition at the same time.

A diagnosis is based on the pattern of symptoms, medical history and examination. Tests or imaging may be needed if symptoms are unusual, worsen rapidly or suggest an alternative or additional condition.[1]

Inflammatory Arthritis

Inflammatory arthritis includes conditions such as rheumatoid arthritis and psoriatic arthritis. Gout and calcium pyrophosphate crystal arthritis—sometimes called pseudogout—can also cause joint inflammation.

Features that may suggest inflammation include:

  • visible or persistent joint swelling
  • warmth around the joint
  • stiffness that lasts longer after waking or resting
  • symptoms affecting several joints
  • fatigue or feeling generally unwell
  • psoriasis or other associated symptoms
  • sudden attacks of severe pain, swelling and tenderness, which may suggest crystal arthritis

These features are not exclusive to inflammatory arthritis. Osteoarthritis can also cause stiffness, swelling and pain at rest.

Blood tests may help with assessment, but they cannot confirm or exclude every form of inflammatory arthritis. In particular, rheumatoid arthritis can be present despite normal inflammatory markers or negative antibody tests. NICE advises specialist referral for persistent inflammation of a joint when the cause is uncertain; investigations should not delay an appropriate referral.[2]

Treatment depends on the particular diagnosis. Some conditions are managed mainly by rheumatology, while others may initially be treated in primary care. If joint replacement is eventually considered, relevant medical and surgical teams can coordinate treatment.

Osteonecrosis of the Hip

Osteonecrosis is also known as avascular necrosis, or AVN. It occurs when the blood supply to part of a bone is disrupted. At the hip, it usually affects the ball at the top of the thigh bone, called the femoral head.

The affected bone can gradually weaken and change shape. In some people it may eventually collapse and lead to secondary osteoarthritis.

Recognised associations include:

  • previous fracture or dislocation of the hip
  • treatment with corticosteroid medicines, particularly higher cumulative exposure
  • high alcohol consumption
  • sickle cell disease and some other blood disorders
  • radiotherapy and certain medical treatments

In some people, no cause is identified. Having one of these risk factors does not mean that osteonecrosis will necessarily develop.

Symptoms can include groin, buttock or thigh pain, stiffness and difficulty putting weight through the leg. Osteonecrosis is more often seen in younger or middle-aged adults than typical hip osteoarthritis, although it can occur at other ages.[3]

An X-ray may appear normal during the early stages. If osteonecrosis is suspected, MRI may be used because it can show changes that are not yet visible on a plain X-ray. Imaging decisions should be made by the responsible clinician according to the individual situation.

Post-traumatic Osteoarthritis

A fracture involving a joint surface, a significant ligament injury or certain cartilage injuries can increase the likelihood of osteoarthritis later in life. Symptoms may develop years or decades after the original injury.

This is often called post-traumatic osteoarthritis. It can occur at a younger age than osteoarthritis that develops without a clear previous injury.

Tell the assessing clinician about significant previous injuries or operations, even if the joint appeared to recover at the time. A previous injury does not prove that it is the cause of current symptoms, but it may be relevant to diagnosis and treatment planning.

Referred Pain

Pain is not always felt at its source. This is called referred pain.

A problem in the lower back can sometimes cause pain in the buttock, hip or leg. Irritation or compression of a nerve may also cause tingling, numbness, burning pain or weakness.

Conversely, a hip-joint problem can cause pain in the thigh or knee, sometimes with little obvious pain directly over the hip. For this reason, an assessment may include the lower back, hip, knee and the rest of the leg rather than only the area in which pain is felt.

The presence or absence of back pain does not reliably establish where the symptoms originate. A clinical assessment is needed when the source is uncertain.

Pain from Muscles, Tendons and Other Nearby Structures

Conditions involving tissues around a joint can produce symptoms similar to osteoarthritis.

Examples around the hip include:

  • greater trochanteric pain syndrome, which commonly causes tenderness and pain over the outer hip
  • gluteal tendinopathy
  • pain arising from the muscles at the front or inner part of the hip
  • an inguinal hernia

Examples around the knee include:

  • irritation of tendons or bursae around the knee
  • pes anserine pain, usually felt on the inner side below the knee
  • iliotibial-band-related pain on the outer side
  • pain arising from the kneecap and surrounding tissues
  • a meniscal or ligament injury

Pain location can provide useful clues but is not completely reliable. Outer-hip pain, for example, may occur with greater trochanteric pain syndrome, hip osteoarthritis or both.

Many soft-tissue conditions are initially managed without surgery using an individual combination of advice, appropriate exercise, load or activity adjustment and pain management. Treatment should be based on the diagnosis and the person’s circumstances.

Other Conditions a Clinician May Consider

Depending on the symptoms, age, medical history and examination, other possibilities may include:

  • a fracture, including a stress or insufficiency fracture
  • infection within or around a joint
  • a problem affecting circulation or nerves
  • pain arising from another joint
  • complications from a previous operation or joint replacement
  • much less commonly, a bone or soft-tissue tumour

The fact that a clinician considers an alternative diagnosis does not mean that a serious condition is likely. It means that the assessment is being tailored to the symptoms rather than assuming that all pain is osteoarthritis.

When to Obtain Urgent Help

Seek same-day advice

Contact NHS 111 or request an urgent GP assessment if:

  • severe pain in one joint starts suddenly
  • a joint becomes hot, markedly swollen or the skin changes colour
  • joint pain is accompanied by fever, shivering or feeling generally unwell
  • you suddenly become unable to put weight through the leg without an obvious explanation

These symptoms can occur with joint infection or another condition requiring prompt assessment. Septic arthritis is uncommon but needs treatment as soon as possible.[4]

After an injury

Call 999 or attend an emergency department after a fall or other significant injury if:

  • the hip or knee appears deformed
  • you have severe pain and cannot stand or walk
  • the injured leg appears shorter or is sitting at an unusual angle
  • you have loss of feeling, a cold or pale foot, or uncontrolled bleeding

Arrange a prompt GP appointment

Contact your GP if you develop:

  • persistent or progressively worsening bone or joint pain
  • unexplained weight loss
  • an unexplained lump or swelling
  • new bone pain when you have a current or previous diagnosis of cancer
  • persistent night pain that is unusual for you
  • symptoms that are not improving as expected

Pain at night can occur with osteoarthritis and many other non-cancerous conditions. Night pain alone does not mean that cancer is present, but persistent or unusual symptoms should be assessed.[5]

Important Information

This article provides general educational information. It cannot determine the cause of an individual’s symptoms and does not replace assessment or advice from an appropriately qualified healthcare professional.

Symptom lists are not diagnostic checklists. Serious causes of hip or knee pain are much less common than osteoarthritis and other musculoskeletal conditions, but prompt assessment is appropriate when the symptoms described above are present.

If you are uncertain how urgently to seek help in England, contact NHS 111 for advice. Emergency arrangements differ in other parts of the UK and outside the UK.

References

  1. National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management. NICE guideline NG226. Published 19 October 2022. Available from: https://www.nice.org.uk/guidance/ng226 [Accessed 14 August 2026].
  2. National Institute for Health and Care Excellence. Rheumatoid arthritis in adults: management. NICE guideline NG100. Published 11 July 2018; last updated 12 October 2020. Available from: https://www.nice.org.uk/guidance/ng100 [Accessed 14 August 2026].
  3. Royal National Orthopaedic Hospital NHS Trust. A patient’s guide to avascular necrosis (AVN). Available from: https://www.rnoh.nhs.uk/patients-and-visitors/patient-information-guides/patients-guide-avascular-necrosis-avn [Accessed 14 August 2026].
  4. NHS. Septic arthritis. Available from: https://www.nhs.uk/conditions/septic-arthritis/ [Accessed 14 August 2026].
  5. NHS. Symptoms of bone cancer. Available from: https://www.nhs.uk/conditions/bone-cancer/symptoms/ [Accessed 14 August 2026].

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