What Causes Knee Pain?

Different knee conditions cause different types of knee pain, felt in different areas of the knee. Some knee pain is accompanied by swelling or heat. A few of the most common knee disorders are discussed below.

What Is Osteoarthritis?

Osteoarthritis is the breakdown of the articular cartilage, the tissue that cushions and protects the ends of bones. This cartilage, like a sponge, compresses under the pressure of each step and resumes original thickness when the force is released. When the cartilage degenerates—due to wear and tear or injury—bone rubs against bone, causing intense pain. Untreated, osteoarthritis of the knee can cause severe pain and loss of joint motion.

What Is Tendonitis?

Tendons are cords of dense tissue that connect muscle to bone. Tendonitis (ten-duh-NIGH-tis) is inflammation in a tendon. Aging causes tendons to grow stiffer and more prone to tendonitis. Tendonitis is also commonly caused by intense sport activities, such as basketball.

What Are Meniscus Injuries?

The meniscus is a C-shaped pad of cartilage covering the top of the tibia (shinbone). The meniscus helps cushion the knee during movement. It also works with the articular cartilage to fit the leg bones together. The meniscus is tough, but it can tear when placed under too much pressure. A meniscus tear can cause pain and swelling. It may also cause the knee joint to catch or “lock.”

What Are Ligament Injuries?

Ligaments are bands of soft tissue that support the knees. The anterior cruciate ligament (ACL) stabilizes the center of the knee. It can be injured when the foot is planted but the body twists. The medial collateral ligament (MCL) on the inside of the knee can be injured by a side blow. This is common in many sports, such as football or soccer.

What Is Bursitis?

Bursae (BUR-say) are small fluid-filled sacs that cushion the movement of bones against muscle, skin, or tendons. Bursitis (bur-SIGH-tis) is inflammation of one or more of these sacs. Three bursae around the knee become inflamed most often:

The prepatellar bursa (on top of the patella, or kneecap) can be inflamed by prolonged kneeling, or by sharp impact to the knee.

The infrapatellar bursa (under the bottom edge of the patella) can be injured by repetitive kneeling, or kneeling with weight applied to the upper shin, or repetitive motion of the knee.

The anserine bursa (under tendons on the inner side of the knee) can be inflamed just by walking. This might occur if you are obese, have tight hamstring muscles, have knees with a natural turnout, or have changed how you walk in response to a joint problem.

What Are the Symptoms?

Symptoms of Osteoarthritis

  • Intermittent or steady pain that gets worse at night or with walking

  • Swelling or tenderness

  • Stiffness when you get up from sitting or lying down

  • Grinding or crunching sounds, sometimes accompanied by pain

Symptoms of Tendonitis

  • Pain above or below the kneecap, where tendons attach to bone

  • Pain that recurs with certain activities and eases with rest

  • In severe cases, pain that no longer improves with rest

Symptoms of Meniscus Injuries

  • Pain and swelling in the knee joint

  • Knee joint catches or “locks”

Symptoms of Ligament Injuries

  • Pain and weakness in the knee joint

  • Feeling as if your knee won’t hold you up

Symptoms of Bursitis

  • Swelling, heat, and tenderness on the kneecap

  • Pain just above the shin and below the kneecap, which increases with activity

  • Pain a few inches below the kneecap that worsens when you climb stairs or exercise, and often hurts more at night

When Should I Get Help?

Minor knee pain may go away with rest, ice, compression (wrapping it in an elastic bandage, but not too tightly), and elevation (which helps to reduce swelling). You can remember this course of treatment by the acronym RICE.

Reference: Arthritis section on Better Medicine

Did You Know?

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