Knee Pain: Why the Knee Joint Hurts

Knee pain is a symptom that occurs in a wide variety of conditions: from a strain after a workout to osteoarthritis and joint infection. The character of the pain suggests where to look, but does not establish a diagnosis. Below is what is known about the causes and when a doctor is needed.

How the knee joint is structured

The knee joint connects the femur, the tibia, and the patella — the kneecap. It is complex: three bones, menisci inside, movement powered by muscles and tendons. Ligaments — collateral and cruciate — limit movement; the cruciate ligaments lie within the joint cavity and prevent the lower leg from shifting excessively forward or backward. Flexion and extension provide about 151 degrees, and in the bent position rotation is added — approximately 15 degrees, passively up to 35.

Bone, cartilage, ligament, tendon, synovial bursa — any of these structures, when damaged or diseased, causes pain and makes walking difficult. Knee problems are very common and occur at any age.

Why the knee may hurt: main causes

The causes fall into two groups: pain after an injury and pain without an obvious injury. After overstretching, overloading, or twisting, often during a workout, it is usually a sprain and overexertion. Pain between the patella and the tibia, typical of repetitive running and jumping, is a sign of tendinitis. The most common knee disease is osteoarthritis: cartilage gradually wears away, and pain and swelling appear. A common sports injury is damage to the anterior cruciate ligament during a sudden twisting movement.

• The knee gives way, does not straighten, and a pop may occur at the moment of injury — damage to a ligament, tendon, meniscus, or cartilage.
• The patella has changed shape after a blow or a sudden change of direction — patellar dislocation.
• Pain and stiffness in both knees, slight swelling, more often in older people — osteoarthritis.
• The skin around the knee is warm and red, and bearing weight on the knees and bending the leg are more painful — bursitis.
• Swelling, warmth, and bruising, especially while taking anticoagulants — bleeding into the joint.

Separately — a hot and red knee with a sudden attack of very severe pain: this is how gout or septic arthritis (joint infection) manifests.

Character of the pain: sharp, aching, throbbing, burning

Sharp, acute knee pain is typical of a cruciate ligament tear: blood flows into the joint, it swells, and the moment of injury is sometimes unnoticed — later a feeling of instability appears. The doctor needs to be told where it hurts, when it started, and what makes the pain worse.

Knee pain in children and adolescents

Knee problems occur at any age, and children are no exception. In adolescents and young adults, pain and swelling below the kneecap is the typical picture of Osgood-Schlatter disease. Children and adolescents also have other conditions, including osteochondritis dissecans, and in active ones, ligament and meniscus injuries, which are classified as sports injuries. If the pain persists, a doctor's examination is needed.

Pain around the knee

It is not always the joint itself that hurts. In bursitis, the synovial bursa becomes inflamed: the area around the knee is warm and red, and bending and kneeling increase the pain and swelling. Iliotibial band syndrome and Baker's cyst also occur.

When knee pain requires seeing a doctor

Knee pain on its own is not a reason to call an ambulance; 103 or 112 — if the knee was injured in a serious accident (for example, in a road traffic collision) or there are signs of a life-threatening condition — stroke, heart attack.

You should see a doctor urgently if the knee is very painful, cannot move or bear weight, is severely swollen or has changed shape, locks, gives way, or clicks painfully. Also — if a very high temperature is combined with redness and heat around the knee: this may be a sign of infection. A routine reason is pain that does not resolve within a few weeks: at the appointment they determine what hurts and how, and may refer for an X-ray, MRI, or arthroscopy — an examination of the joint from the inside.

This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer