Book PTRU

Does your knee hurt?

Find out why with our algorithm.

Start

Clinical disclaimer: This algorithm is a decision-support tool and does not replace individualised clinical assessment. Recommendations should always be interpreted in context by the treating physician. If in doubt, consult an orthopaedic specialist.

What it is

Knee Pain Always Has a Cause

Gonalgia is the medical term for knee pain. It is not a diagnosis: it is a symptom, which may come from the bone, the cartilage, the menisci, the ligaments, the tendons or the joint itself. The same pain may be a tendinopathy in a young athlete or the start of osteoarthritis in an older person — and the right treatment depends on identifying the source.

The algorithm above helps to guide the initial reasoning based on your complaints. It does not replace clinical examination, but it points to the most likely path and the degree of urgency.

Osteoarthritis is one of the causes of knee pain — not the only one. Knee pain is not synonymous with "wear and tear".

The most common causes

Where the Pain May Come From

Each cause has its own pattern of pain, typical age and treatment. Click to understand yours.

Osteoarthritis (gonarthrosis) →

Wear of the articular cartilage, more common from the age of 50. Mechanical pain and brief morning stiffness.

Meniscus tear →

Pain along the joint line, sometimes with locking or a sense of giving way. May be traumatic or degenerative.

ACL injury →

A sprain with a pop and rapid swelling, with a sense of instability. Common in sport.

Cartilage lesions →

Focal cartilage damage, with localised pain and recurrent effusion.

Patellar tendinopathy →

Pain at the front of the knee, in the tendon, aggravated by jumping and squatting.

Iliotibial band syndrome →

Pain on the outer side of the knee, typical of runners and cyclists.

Kneecap (patellar) instability →

A kneecap that "jumps" or slips out, with pain at the front of the knee.

Baker's cyst →

Swelling and a sense of tightness at the back of the knee.

Parameniscal cysts →

Small cysts associated with meniscus injuries.

⚠ Red flags — when to seek urgent help

  • Trauma with obvious deformity or inability to bear weight.
  • A locked knee that will neither straighten nor bend.
  • Sudden, severe swelling immediately after trauma.
  • Fever, warmth and marked redness of the knee (suspected infection).
  • Severe pain that does not ease with rest or with analgesia.
Frequently Asked Questions

Questions about Knee Pain

It is the medical term for knee pain, wherever it comes from. It is a symptom, not a diagnosis — so the next step is always to work out which structure is responsible (bone, cartilage, meniscus, ligament, tendon or kneecap).
No. Osteoarthritis is a common cause from the age of 50, but the pain may come from the menisci, the ligaments, the cartilage, the tendons or the kneecap. In young people it is rarely osteoarthritis — a sports injury or a problem of the extensor mechanism is far more likely.
It starts with the clinical history and the physical examination, which guide the diagnosis in most cases. An X-ray assesses the bone and osteoarthritis; MRI shows the menisci, ligaments and cartilage when needed. Not all knee pain requires an MRI.
Seek urgent assessment if there is trauma with deformity or inability to bear weight, a locked knee, sudden and severe swelling, fever with warmth and redness, or pain that does not ease with rest and analgesia. Short of these signs, pain persisting for more than 4 to 6 weeks warrants a planned assessment.
No. Most causes of knee pain are treated without surgery — with rehabilitation, weight control, activity adjustment and, when indicated, medication or injections. Surgery is reserved for cases where conservative treatment does not resolve the problem or where there is a structural injury that requires it.
Seek assessment if pain lasts more than 2–3 weeks, if there was trauma with swelling, if the knee locks, gives way or cannot bear weight, or if there is redness and fever. Early assessment prevents treatable problems (meniscus, ligaments, cartilage) from progressing.
No. Knee pain has many causes — meniscus, ligament (ACL) or cartilage injuries, tendinopathies, patellar instability, or pain referred from the hip/spine. The correct diagnosis depends on history, examination and, when needed, imaging.
The cost depends on the treatment pathway. SIGIC (Portuguese NHS): with a surgery voucher, the procedure is fully covered — no cost to the patient. Health insurance / subsystems: contracted surgery, according to your plan. Private: a personalised quote — as a guide, from €3,000 for arthroscopy (meniscus, ligaments or cartilage, including anterior cruciate ligament reconstruction) and from €8,000 for knee replacement. Final prices depend on the clinical case, hospital and implants. For an exact quote, book an appointment or see prices & quotes.

Knee pain that will not go away?

A specialist assessment identifies the cause of your knee pain and defines the treatment appropriate to your case.

Book a Consultation 926 850 194
Dr. Nuno Camelo Barbosa
Dr. Nuno Camelo Barbosa
Orthopaedic surgeon · Knee surgery subspecialty
Peer reviewer (AJSM · KSSTA · OJSM · JEO)
Last medically reviewed: 24 July 2026
Full profile  ·  Book appointment →