Family Health: Knees most vulnerable joint in body

Knee pain is among the most common reasons people go to their doctors – and if you look at the anatomy of this joint, you can see why.

Knees lack the bony protection of a ball-and-socket joint, yet they carry most of your weight and absorb the impact when you walk, run or jump. As hinge joints, they bend in only one plane of motion. And while a network of strong ligaments works to keep your knees stable, they are still the most vulnerable joints in your body.

That vulnerability often shows up as pain that begins gradually and gets worse over time. Since even a moderately active person walks between 3,000 and 4,000 steps in a day, it’s easy to see how eventually the protective, shock-absorbing tissue that covers the bone surfaces inside the joint starts to wear out. This is what happens with osteoarthritis, the most common cause of knee pain in people age 50 and older. If you’re in this age group, suspect osteoarthritis if your knee pain is worse in the morning, gets better as you start moving around, but returns if you get more active.

Younger people can also have low-level knee pain that gradually gets worse. It often comes from overuse injuries such as:

  • Bursitis. Inside your knee are sacs called bursa that produce lubricating fluid. If they become irritated from overuse, or from kneeling for long periods, they can become painfully inflamed.
  • Tendonitis, or “jumper’s knee.” The patellar tendon connects your thigh muscle to your tibia, or shin bone, and works to straighten your knee. Training too hard or too quickly can cause it to weaken and be painful when you run, jump or climb stairs.
  • Chondromalacia, or patellofemoral pain syndrome. Running and jumping sports that involve repeated stress to your knee can lead to this condition. So can weak muscles and trauma to the kneecap, or patella. It results in dull pain around or under the kneecap that gets worse when you go down stairs, kneel or sit for long periods with a bent knee.

Osteoarthritis and overuse injuries often improve if you make certain lifestyle changes. For example, low-impact exercises to strengthen your muscles can relieve pain and disability. If you’re overweight, losing pounds can make a big difference.

When knee pain starts suddenly, it’s usually easy to link it with an activity. Think of landing hard after a jump, the quick starts and stops in basketball or soccer, or any movement that twists your knee. Activities like these, as well as a blow to the knee, can cause acute injuries such as:

  • Torn meniscus. The meniscus cartilage is the shock absorber of your knee. There are two in each knee, and they can tear from sudden movements, especially twisting, or because they are weakened from age or arthritis. Pain may be mild unless a fragment of meniscus catches inside the joint.
  • Sprained or torn ligament. There are four ligaments in each knee that keep the joint stable. They can be injured or even completely torn, causing pain or a popping sensation. In some cases, there is little or no pain, but your leg may buckle under your weight. The infamous ACL, or anterior cruciate ligament, tear, usually happens from a sudden twisting motion.
  • Muscle strain. Pain near the front or back of the knee can come from strained thigh muscles – the quadriceps in front or the hamstrings in the back. Suspect muscles strain, or “pulled muscles,” after activities that require sudden stops and starts.

Treatment for acute knee pain often starts with "RICE" – rest, ice, compression and elevation – along with an over-the-counter pain reliever such as ibuprofen or acetaminophen. Put your knee up and use a bag of ice or frozen vegetables to control swelling. An elastic bandage or sleeve can also reduce swelling and help your knee feel more stable. Rest means avoiding the activities make your pain worse. It doesn’t mean staying in bed – unused muscles lose strength quickly, and that can make your knee problem worse.

Many knee problems, from both overuse and acute injury, heal with home treatment and gradual strengthening exercises. But you should still see your doctor to rule out a more serious condition, and to get on track for the right treatment. For example, knee bursitis sometimes is caused by an infection, which requires antibiotic treatment.

Physical therapy is often prescribed to help knee pain, and in some cases surgery is necessary. According to the American Academy of Orthopedic Surgeons, you should get treatment as soon as possible if you:

  • Hear or feel a popping noise, or you knee gives way with your injury.
  • Have severe knee pain.
  • Can’t move your knee.
  • Can’t walk without limping.
  • Have swelling in your knee.

Less common conditions, such as cysts and infections, can also cause knee pain. Find out more by visiting the AAOS at