Internal derangement of the knee is a broad term for a knee problem inside the joint that causes pain or makes it hard to move your knee normally.

Different issues can lead to internal derangement of the knee. Tears within the knee or a loss of the coating on the ends of bones (cartilage) can play a role. So can having bits of bone and cartilage that have broken loose in the knee. These problems can be caused by:

• Injury. This includes sudden twisting or a hard impact to the knee.
• Frequent knee strain. Playing some sports, crouching or squatting, heavy lifting, and climbing stairs can all cause it.
• Aging. Arthritis and wear and tear over time can also be a cause.

If you have a sudden (acute) injury, some symptoms may include:

• Severe pain or a "popping" feeling your knee.
• A sudden feeling of instability.
• Swelling and bruising around your knee.

If you have a chronic or overuse injury, some symptoms may include:

• Pain or discomfort in your knee that has increased over time.
• Pain after doing certain activities or at night.
• Locking or buckling of your knee.

Your doctor will ask you questions about your symptoms and do a physical exam. This exam involves checking your range of motion and strength, as well as how much weight your knee can bear. Other tests may include X-rays, an MRI, or an ultrasound.

Your treatment will depend on what caused the problem.

Common treatments include:

• The RICE method (Rest, Ice, Compress, and Elevate the knee).
• Medicines to reduce pain and swelling or treat related conditions, like arthritis.
• Physical therapy to strengthen the knee or muscles that support the knee.
• Injections (corticosteroids) to reduce pain and swelling.

If these treatments don't work, your doctor may recommend surgery. The type of surgery you need will also depend on your diagnosis.

• Arthroscopic surgery. A surgeon uses small cuts to guide a special camera and small tools into the knee to fix it.
• Open surgery. A surgeon uses a larger cut in the knee to fix it, like for a fracture.
• Partial or total knee replacement. This may be used if repair isn't an option.

After any knee surgery, physical therapy is recommended to rebuild muscle and improve strength.