The knee is a mobile, complex joint between the femur (thigh bone) and tibia/fibula (leg bones). It not only bends like a hinge but also rotates slightly. (Sit in a chair and pivot your forefoot in and out to your heel.  You can feel your tibia rotate under your femur.)  Ligaments help control excess knee motion by connecting the bones and supporting the joint. Muscles and tendons around the knee also help stabilize the joint and can prevent (or contribute to) injury. Cartilage and menisci within the joint cushion the knee and act as shock absorbers and stabilizers. There is also a covering (aka Capsule) around the joint that holds in the joint fluid (synovial fluid) made by seaweed like tissue (synovium).  When you injure your knee, the body secretes more fluid that is contained in the capsule and makes the joint feel "puffy."

There are several important ligaments around and inside the knee joint. The most infamous is the ANTERIOR CRUCIATE LIGAMENT (ACL). The ACL crosses from the back of the femur to the front of the tibia in a manner similar to the alignment of your forearms when you place your hands in your front pocket.  The ACL helps prevent the tibia from sliding forward relative to the femur. The ACL can be injured when you twist your knee beyond its normal range of motion, as when you pivot while standing firmly on your foot or when you "catch an edge" while skiing causing your lower leg to rotate suddenly. You may hear or feel a "pop" that is often a tell-tale sign of an ACL injury or kneecap dislocation. 

The MEDIAL COLLATERAL LIGAMENT (MCL) connects the femur to the tibia along the inside of your knee. The MCL has fibers that attach directly to the meniscus, a rubbery ring inside the knee joint that acts like a gasket or stabilizing ring. Meniscal tears often occur with age and usually do not cause pain.  Painful meniscus injuries often follow trauma such as after a fall or twisting injury. Meniscal tears will sometimes "flip or slip" in between the femur and tibia bones, causing the joint to "catch or lock" the joint. This unique situation usually needs surgery but not all tears need to be repaired.

The LATERAL COLLATERAL LIGAMENT (LCL) stabilizes the knee from bending sideways. This can be strained as well and often does not require surgical repair.

A ligament may be stretched (Grade 1 sprain), partially torn (Grade 2 sprain) or completely torn (Grade 3 sprain). Depending on your specific situation, the ligaments and menisci may or may not need surgical repair. Grade 1 and 2 sprains usually rehabilitate well without surgery.

CARTILAGE usually "caps" the ends of bones and allows for smooth joint gliding and shock absorption. Overuse, trauma, and wear-and-tear (aka "seasoning") can injure cartilage. This is called osteoarthritis. Frequently people feel a grinding sensation when cartilage is worn inside the joint. There are abundant nonsurgical treatment options to treat this and prevent further degeneration. Carefully assessing the biomechanics of the joint and preventing further injury is key to proper rehabilitation. Injecting "lubricant" into the knee joint may be helpful for some arthritis sufferers.

There are other more unusual causes for knee pain that will not be discussed in this brief newsletter. Finding the right diagnosis is vital for determining the best treatment options and prevention strategies. At Spine West we use thorough physical exam techniques and diagnostic tools such as ultrasound, x-ray, and MRI to help determine the problem and possible treatments.  Many people think they need to see an orthopaedic surgeon for their joint problems. They do if they desire or need surgery. Physiatrists are experts in diagnosing and treating these conditions non-surgically.  Call us if you have questions.

Written by Cliff Gronseth, M.D.