Jumper's knee — also known as patellar tendonitis or patellar tendinopathy — is an inflammation or injury of the patellar tendon, the cord-like tissue that joins the patella (kneecap) to the tibia (shin bone). Jumper's knee is an overuse injury (when repeated movements cause tissue damage or irritation to a particular area of the body).

Constant jumping, landing, and changing direction can cause strains, tears, and damage to the patellar tendon. So people who regularly play sports that involve a lot of repetitive jumping — like track and field (particularly high-jumping), basketball, volleyball, gymnastics, running, and soccer — can put a lot of strain on their knees.

Jumper's knee can seem like a minor injury that isn't really that serious. Because of this, many athletes keep training and competing and tend to ignore the injury or attempt to treat it themselves. But it's important to know that jumper's knee is a serious condition that can get worse over time and ultimately require surgery. Early medical attention and treatment can help prevent continued damage to the knee.

How Does the Knee Work?

To understand how jumper's knee happens, it helps to understand how the knee works. The knee, which is the largest joint in the body, provides stability to the leg and allows it to bend, swivel, and straighten. Several parts of the body interact to allow the knee to function properly:

• Bones like the femur (thighbone), the tibia (shinbone), and the patella (kneecap) give the knee the strength needed to support the weight of the body. The bones that meet at the knee allow it to bend smoothly.
  
• Muscles provide the tug on the bones needed to bend, straighten, and support joints. The muscles around the knee include the quadriceps (at the front of the thigh) and the hamstring (on the back of the thigh). The quadriceps muscle helps straighten and extend the leg, and the hamstring helps bend the knee.
  
• Tendons are strong bands of tissue that connect muscles to bones. The tendons in the front of the knee are the quadriceps tendon and the patellar tendon. The quadriceps tendon connects to the top of the patella and allows the leg to extend. The patellar tendon connects to the bottom of the kneecap and attaches to the top of the tibia.
  
• Similar to tendons, ligaments are strong bands of tissue that connect bones to other bones.

By working together, bones, muscles, tendons, and ligaments enable the knee to move, bend, straighten, provide strength to jump, and stabilize the leg for landing.

About Jumper's Knee

When the knee is extended, the quadriceps muscle pulls on the quadriceps tendon, which in turn pulls on the patella. Then, the patella pulls on the patellar tendon and the tibia and allows the knee to straighten. In contrast, when bending the knee, the hamstring muscle pulls on the tibia, which causes the knee to flex.

In jumper's knee, the patellar tendon is damaged. Since this tendon is crucial to straightening the knee, damage to it causes the patella to lose any support or anchoring. This causes pain and weakness in the knee, and leads to difficulty in straightening the leg.

Symptoms

Common symptoms of jumper's knee include:

• pain directly over the patellar tendon (or more specifically, below the kneecap)
• stiffness of the knee, particularly while jumping, kneeling, squatting, sitting, or climbing stairs
• pain when bending the knee
• pain in the quadriceps muscle
• leg or calf weakness

Less common symptoms include:

• balance problems
• warmth, tenderness, or swelling around the lower knee

Treatment

Jumper's knee is first evaluated by a grading system that measures the extent of the injury (grades range from 1 to 5, with grade 1 being pain only after intense activity and grade 5 being daily constant pain and the inability to participate in any sporting activities).

While examining the knee, a doctor or medical professional will ask the person to run, jump, kneel, or squat to determine the level of pain. In addition, an X-ray or MRI might be recommended. Depending on the grade of the injury, treatment can range from rest and icepacks to surgery.

For mild to moderate jumper's knee, treatment includes:

• resting from activity or adapting a training regimen that greatly reduces any jumping or impact
• icing the knee to reduce pain and inflammation
• wearing a knee support or strap (called an intrapatellar strap or a Chopat strap) to help support the knee and patella. The strap is worn over the patellar tendon, just beneath the kneecap. A knee support or strap can help minimize pain and relieve strain on the patellar tendon.
• elevating the knee when it hurts (for example, placing a pillow under the leg)
• anti-inflammatory medications, like ibuprofen, to minimize pain and swelling
• massage therapy
• minimum-impact exercises to help strengthen the knee
• rehabilitation programs that include muscle strengthening, concentrating on weight-bearing muscle groups like the quadriceps and calf muscles
• specialized injections to desensitize nerve endings and reduce inflammation

On rare occasions, such as when there's persistent pain or the patellar tendon is seriously damaged, jumper's knee requires surgery. Surgery includes removing the damaged portion of the patellar tendon, removing inflammatory tissue from the lower area (or bottom pole) of the patella, or making small cuts on the sides of the patellar tendon to relieve pressure from the middle area.

After surgery, a rehabilitation program involving strengthening exercises and massage is followed for several months to a year.

Recovery

Recovering from jumper's knee can take a few weeks to several months. It's best to stay away from any sport or activity that can aggravate the knee and make conditions worse.

But, recovering from jumper's knee doesn't mean that someone can't participate in any sports or activities. Depending on the extent of the injury, low-impact sports or activities can be substituted (for instance, substituting swimming for running). Your doctor will let you know what sports and activities are off-limits during the healing process.

Preventing Jumper's Knee

The most important factor in preventing jumper's knee is stretching. A good warm-up regimen that involves stretching the quadriceps, hamstring, and calf muscles can help prevent jumper's knee. It's always a good idea to stretch after exercising, too.

Reviewed by: Alfred Atanda Jr., MD
Date reviewed: March 2010