Your knees are two of the largest, most heavily used joints in your body. It's no wonder, then, that knee pain is both pretty common and pretty hard to ignore.

"In many cases, knee pain can be treated at home via stretching and strengthening exercises," says Dr. Kenneth Brooks, orthopedic surgeon specializing in knee surgery at Houston Methodist. "However, some types of knee pain can also be the result of a serious injury that requires evaluation and treatment by a specialist."

Whether your knee pain is due to aging, overuse, muscle tightness or muscle weakness, Dr. Brooks is here to help you understand how to alleviate your pain, as well as the signs indicating that it may be a sign of serious injury.

Common causes of knee pain

Your knee is a complex joint, and pain can occur as a result of problems in the knee itself, as well as tightness or weakness in the muscles or inflammation in the tendons surrounding it.

Common causes of knee pain include:

• Knee arthritis – pain while bearing weight or in motion, as well as stiffness and pain you feel while moving your knee out of a position it's been in for an extended period of time
  
  
• Tendonitis of the quadricep or patella tendon – tenderness or tightness either above the kneecap (quadriceps tendonitis) or below it (patellar tendonitis), which may worsen after prolonged sitting, bending, jumping, or squatting
  
  
• Anterior knee pain – pain around or under your knee cap that can cause stiffness in the knee when sitting, discomfort after prolonged running or hiking, and sensations of popping, grinding or crunching
  
  
• Knee injury – sudden onset of pain accompanied by some level of damage to the meniscus or ligaments that cushion and stabilize the knee joint, respectively

"Most types of knee pain can typically be self-managed at home through over-the-counter pain relievers and stretching and strengthening exercises that help improve knee mobility and stability," says Dr. Brooks.

Improving joint mobility involves daily stretching and flexibility-improving exercises. Improving stability entails strengthening the muscles that help support your knee, including your core muscles, gluteal/hip muscles, quadriceps muscles, hamstring muscles, and calf muscles.

Exercises to help relieve knee arthritis pain

The most common cause of knee arthritis is osteoarthritis, which becomes more common with increasing age. Over time, the cartilage in your knee joint wears away — causing pain and tenderness while using your knee.

"The stronger your leg muscles are, the more they can help cushion your knee joint during impact and during exercise," explains Dr. Brooks.

But, you've likely already noticed that some common leg-strengthening workouts, such as running or jumping, actually worsen your knee pain.

"High-impact weight-bearing exercises aren't recommended for people whose knee pain is due to arthritis," says Dr. Brooks.

Instead, Dr. Brooks recommends improving your knee mobility by stretching regularly — especially your quadriceps, hamstring, and calf muscles — and increasing your knee stability by performing low-impact leg strengthening exercises, such as:

• Riding an exercise bike
• Using an elliptical
• Swimming
• Water-based workouts, such as walking, high-stepping, kickboarding or other exercises you can perform while holding on to the ledge of the pool

"Performing water-based exercise is a really good way for a person with arthritis in the knee to maintain his or her overall fitness," explains Dr. Brooks. "The buoyancy effect of water can relieve the pressure on the joints, making conditioning and strengthening exercises much more comfortable."

Exercises to help relieve patellar tendonitis or quadriceps tendonitis

Another very common type of knee pain occurs when the tendons that are connected to your kneecap become inflamed (called tendonitis). Patellar tendonitis, also called "jumper's knee," results in pain at the base of your kneecap, while quadriceps tendonitis results in pain at the top of your kneecap.

The patellar and quadriceps tendons help straighten your kneecap as you extend your leg. When used repetitively or when placed under excess pressure as a result of weak hamstring and/or quadriceps muscles, painful inflammation of the tendons can result.

To help relieve knee pain caused by tendonitis, focus on gently stretching and strengthening your hamstring and quadriceps muscles.

"With knee-related tendonitis, resisted knee extension exercises should be avoided, since this movement applies stress to the quadriceps and patellar tendons, as well as the kneecap," explains Dr. Brooks. "In addition, cycling may cause pain, since the constant bending repetitively stretches your already inflamed tendon."

Instead, Dr. Brooks recommends the elliptical as a great way to maintain your fitness without worsening your knee tendonitis pain. An elliptical machine keeps your knee in a neutral position, reducing the amount of tension placed on these tendons.

Exercises to relieve anterior knee pain

Knee pain that occurs due to muscle weakness or tightness can be hard to pin down, but one thing is for sure: Anterior knee pain is common.

"When someone is experiencing anterior knee pain, he or she will often grab or point to the kneecap when describing where the pain is located," says Dr. Brooks. "Generally speaking, it's pain around or under the kneecap."

According to Dr. Brooks, anterior knee pain is most commonly caused by arthritis under the kneecap or tightness or weakness in one or more of the following muscles:

• Core muscles – as this places additional weight-bearing stress on the lower back (bringing the hips out of alignment and altering knee position) and quadriceps muscles (for knee and, thus, limb stability)
  
  
• Gluteal/hip muscles – as this causes the hips to turn inward, placing a sideways stress on the kneecap and quadriceps muscles and tendon
  
  
• Hamstring muscles – as this causes an imbalance in the muscle forces across the knee, placing more stress on the quadriceps muscles for knee movement and stability
  
  
• Quadriceps muscles – as weakness places more stress on the bone and joint itself to maintain stability; tightness prevents full movement or excursion of the tendons, applying greater pressure to the kneecap

In addition, anterior knee pain can be caused by IT band tightness in runners, cyclists and hikers.

"Since anterior knee pain can be caused by issues with quite a few of the muscles supporting the knee, it's important to regularly stretch these muscles if you're experiencing this type of pain," recommends Dr. Brooks. "In addition, strengthening these muscles through closed chain exercises can help better cushion and support the knee joint as a whole, relieving pain."

Closed-chain leg strengthening includes exercises where your foot remains in contact with the surface you're exercising on, such as:

• Walking
• Elliptical
• Knee presses
• Squats

"Unless you're maintaining a comprehensive stretching program, you should avoid running, cycling or knee-extension exercises if you have anterior knee pain," Dr. Brooks warns.

See a doctor for a knee injury, sharp knee pain or knee pain that doesn't improve

While many general causes of knee pain can be managed at home, you'll need to see a doctor if your knee pain is of sudden onset and associated with any one of the following:

• Sudden pop or snap
• Sudden loss of movement
• Sudden swelling
• A feeling of buckling or giving out
• Being stuck in one position and unable to release your knee from that position

These may all be signs of serious knee injury and should prompt a visit with a specialist. One common example of such an injury is a tear of the meniscus, one of the "shock absorbers" in the knee joint.

"A meniscus tear leads to acute pain on the inside or outside of the knee, especially when pivoting or twisting," explains Dr. Brooks. "If the pain is only mild and the knee feels stable, it's generally safe to continue exercising. However, if the pain is sharp and accompanied by sensations of buckling, giving out or getting stuck, it needs to be evaluated by a specialist."

In addition, if you have general knee pain that doesn't go away after about 4 to 6 weeks of self-management, it's probably time to schedule a visit.