Why Does My Knee Hurt? Common Causes Explained

Name: Why Does My Knee Hurt?
Creator: Dr. Chetan M. Dojode

Knee pain is common enough that it is often dismissed, and varied enough that it is often misattributed. The location of the pain, your age, and the circumstances in which it appears usually narrow the likely cause considerably before any scan is required.

Pain felt at the front of the knee, worse on stairs, after prolonged sitting, or when squatting, most often relates to the patellofemoral joint — the kneecap and its groove. In younger and active people this is frequently a problem of muscle control and load rather than structural damage, and it typically responds well to targeted physiotherapy.

Pain along the inner or outer joint line, particularly with catching or a sense of something moving in the joint, points towards the meniscus. In younger patients this usually follows a specific twisting injury; in older knees, meniscal tissue degenerates and can tear with minimal provocation.

Pain that is diffuse, worse with activity and towards the end of the day, associated with stiffness after rest and gradual loss of movement, suggests arthritis. Night pain and pain at rest indicate more advanced disease. Deformity developing over years — a leg becoming progressively bowed — points the same way.

Some patterns deserve prompt attention rather than watchful waiting: a knee that is hot, red and swollen with fever; a knee that locks and cannot be straightened; a knee that swelled within hours of an injury; or a knee that repeatedly gives way. These warrant assessment rather than a wait-and-see approach.

What the location of pain usually suggests

Front of knee	Patellofemoral pain — worse on stairs, squatting, after prolonged sitting.
Inner or outer joint line	Meniscal problem — catching, clicking, localised tenderness.
Diffuse, whole knee	Arthritis — stiffness after rest, worse with activity, gradual onset.
Behind the knee	Baker's cyst, hamstring or calf origin problems, occasionally referred.
Below the kneecap	Patellar tendinopathy — common in jumping and running athletes.
Giving way	Ligament instability, or quadriceps weakness causing the knee to buckle.

When knee pain should be assessed promptly

Seek assessment without delay if the knee is hot, red and swollen with fever, since infection in a joint requires urgent treatment; if the knee is locked and cannot be fully straightened; if it swelled rapidly within hours of an injury; if it repeatedly gives way; or if you cannot bear weight after an injury. Hip and spinal problems can also refer pain to the knee, which is why the examination is not confined to the knee itself.

Frequently Asked Questions

Why does my knee hurt when climbing stairs?

Stair climbing loads the patellofemoral joint heavily, so pain in this situation commonly relates to the kneecap and its groove. In younger, active people this often reflects muscle control and loading rather than structural damage and responds to targeted physiotherapy. In older patients it may indicate patellofemoral arthritis.

Is knee pain always arthritis?

No. Arthritis is one cause among many. Meniscal problems, ligament injury, patellofemoral pain, tendinopathy, bursitis, inflammatory arthritis and referred pain from the hip or spine all present as knee pain. Age, pain location and symptom pattern usually distinguish them.

Should I rest or exercise a painful knee?

Complete rest is rarely the answer. Most knee conditions improve with appropriate activity and targeted strengthening, particularly of the quadriceps. What changes is the type of loading, not the presence of it. Sudden severe pain, a locked knee, or an inability to bear weight are exceptions requiring assessment first.

Do I need an MRI for knee pain?

Often not. Weight-bearing X-rays are more informative for suspected arthritis, and MRI can be misleading if used first, since it frequently shows degenerate changes and meniscal tears that are not the source of symptoms. MRI is valuable where a specific soft-tissue injury is suspected or surgery is being planned.

When should I see an orthopaedic surgeon about knee pain?

When pain persists beyond a few weeks despite sensible self-management, disturbs sleep, limits walking distance, follows a significant injury, or is accompanied by locking, giving way or rapid swelling. Earlier assessment is worthwhile for injuries in active people, where treatment decisions are time-sensitive.