Your knees are crucial joints held together by ligaments and tendons. Ligaments connect the bones; tendons connect the muscles to the bones. Ligament and tendon injuries can both cause the knees to swell. Identifying where your pain is and when it occurs will help your doctor diagnose your condition. Treatment usually involves resting and icing your knee, cortisone shots, physical therapy and possibly bracing and surgery.
Patellar Tendon
Your patellar tendon connects the quadriceps muscle in your thigh to your shin bone, but it's located between your knee cap and your shin bone. It allows you to straighten your knee. Common patellar-tendon injuries that cause your knee to swell are tears and tendinitis. Tears usually result from falls, direct impact and hard landings from jumping. Tendinitis is an aggravation or inflammation of the patellar tendon that results from running or activity that requires frequent jumping, such as basketball or climbing stairs.
ACL and PCL
The kneecap, thigh bone and shin bone meet at the knee and are held together by a set of four ligaments. The anterior cruciate ligament and posterior cruciate ligaments form an X deep inside the knee and stop your shin from sliding in front or behind your thigh bone. The ACL is injured more frequently than the PCL in sports such as football. Symptoms of a tear in the ACL include swelling, extreme pain and a loud pop at the time of the tear.
MCL and LCL
The other two ligaments in your knee are the medial collateral ligament, located along the inner side of your knee, and the lateral collateral ligament, located on the outer side of your knee. The MCL is injured more frequently than the LCL, according to the University of Pittsburgh Medical Center. Both can tear with a direct impact or sudden twisting of the knee. A partial tear is called a sprain; a complete tear is called a rupture. Sprains and ruptures cause swelling, intense pain, knee locking and a feeling that the knee will give out.
Iliotibial Band Syndrome
The iliotibial band is a tendon that runs along the outer part of your thigh. It starts at the gluteus muscles in your hip and connects to your kneecap and shin bone. The iliotibial band slides over the lower part of your thigh bone when you bend your knee. Frequent flexing from activities such as running can cause irritation to the iliotibial band, which results in swelling and pain that feels like it cuts across the middle of the knee and lower outside part of your thigh.
References
- American Academy of Orthopaedic Surgeons: Patellar Tendon Tear
- University of Pittsburgh Medical Center: Anterior Cruciate Ligament (ACL) Injuries
- University of Pittsburgh Medical Center: Medial Collateral Ligament (MCL) / Lateral Collateral Ligament (LCL) Sprain
- "American Family Physician"; Iliotibial Band Syndrome: A Common Source of Knee Pain; Razib Khaund, M.D., et al.; April 2005
