What is it?

The Knee is the second largest joint of the leg.  It is made up of three bones: the shinbone or tibia, the thighbone or femur, and the patella or kneecap.  These three bones articulate with each other to create the hinge joint that allows you to move your lower leg through its normal range of motion.  In addition, a cartilage pad, called the meniscus, cushions the middle of the joint, and the entire structure is surrounded by a capsule that contains synovial fluid that helps the joint move smoothly,  like oil in and car engine.

The knee joint is far more complex than this, however.  Four separate ligaments connect the bones together to allow for movement.  Two run on either side of the joint, called the collateral ligaments.  Two other ligaments  criss-cross inside the knee joint, the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL).  If any of these structures, from the ligaments to the joint components, suffer trauma or disease, pain can occur.  The pain may be associated with stiffness, locking, and popping of the joint, depending on the injury involved.  The patellar tendon is actually a ligament as it connects the  patella to the tibia.  It can become inflamed and painful in those who do a lot of jumping; in this case,  it is called “Jumper’s knee” and is a serious condition.

There are groups of muscles around the knee, including the hamstring muscles that  flex the knee and the quadriceps muscles that extend it.  Both sets of muscles help to provide stability of the knee.  Each muscle is connected to a bone by a  ropelike tendon, which inserts into the bone around the joint.  Contraction of the muscle causes movement of the joint.   Muscles and tendons can become painful from tears, swelling, and/ or degenerative changes.

Finally, the knee contains fluid filled sacs, called bursae,  that lie between bones and tendons to reduce friction.   These bursae can also become inflamed and painful.  “Housemaids knee”  is one of the most common types of knee bursitis.  It occurs when the bursa below the knee cap becomes irritated, produces too much fluid, and becomes inflamed.   Those who kneel a lot are susceptible, such as those who work on flooring or do gardening.   There is another set of bursa on the inside of the knee, just below the knee joint and beneath the tendons of the hamstring muscles.  These set of bursae are called the pes anserine and can become inflamed and painful with arthritis, injury, or with runners who over train, especially running uphill.

Who gets it?

Anyone is at risk for knee pain.   Arthritis is the number one culprit in causing knee pain, in particular osteoarthritis, which is simple wear and tear of the knee cartilage over time.  Since this joint is used so often, the cartilage can wear thin, particularly in older adults and those who carry extra weight on their frames, causing pain from bone rubbing against bone.  Rheumatoid and other inflammatory types of arthritis usually occur in smaller joints of the body, leaving osteoarthritis as the number one cause of knee pain.

Of course, there are many other reasons that you can have knee pain.  Direct trauma to the knee is very common, particularly in patients who are active in athletics.  The ligaments are in particular danger of damage in football and other contact sports where the legs are hit out from under the player.  In addition, stopping and changing direction rapidly while running can put a great deal of stress on the joint and ligaments.  Skiing is a major cause of ACL injuries.  Even those who have endure car accidents or falls may experience knee pain.  In general, anyone can have pain in the knee, and it can be debilitating enough to cause disability and chronic pain.

What kind of pain results?

The pain involved in knee problems can be complex.  It is usually an aching pain that can radiate down the shin or up towards the hip.  Depending on what it injured, the pain can occur on movement, on weight bearing, or even at rest.  Some knee pain will present as dysfunction with the movement of the joint.  For instance, ligament damage can cause slippage of the tibia out from under the femur, making the knee feel like it is coming apart at the seams.  It will feel almost too loose and you won’t have much control over how your leg bears your weight.

With meniscus problems, you may not experience slippage, but it is certainly possible to feel a locking, when the ragged ends of the cartilage get inside the working parts of the joint.  Popping is also common with cartilage injuries, and you may feel a snapping sensation in your knee when you move it.  Most patients tend to lose their range of motion of the joint, as well, experiencing pain when attempting to extend or flex the knee regardless of weight bearing.

Treatment

Most knee injuries will improve with conservative treatment, such as  rest, ice, compression, and elevation, to heal.  Anti-inflammatory medications, sold over the counter, such as ibuprofen or naproxen, can also help with swelling and reducing pain, as can acetaminophen ( check with your physician before taking any medication, even those sold over the counter).   In more severe circumstances, stronger anti-inflammatories can be used, and physical therapy plays a large part in rehabilitating the knee.  A knee brace may help to provide additional support to the ligaments and tendons of the knee and thereby reduce pain

If your knee pain does not improve with conservative treatment, as described above,  then a Pain Medicine physician can evaluate you to determine the cause of your knee pain.   After a careful examination, imaging studies may be ordered.  An Xray can show arthritis, while an MRI can detect arthritis, fluid accumulation or problems with the soft tissues of the knee. Your Pain Medicine physician can provide a number of treatments that can help you restore function to your knee.  First, steroid injections directly into the knee joint can decrease swelling, inflammation and pain. They can be performed approximately every six months if they are successful in controlling pain.  If steroids do not provide long term relief of knee arthritis pain,  then injection of a synthetic gel into the knee joint can help restore the lubrication to the joint.

Platelet rich plasma injections can help with tendontitis and trigger point injections can help with muscle spasms or myalgias (muscle pain).

You will be referred to an Orthopedic Surgeon for meniscus tears or severe arthritis of the knee that does not improve with injections or for a second opinion as needed.  You may be a candidate for arthroscopic surgery of the knee or even knee replacement.

If  you are told you are not a surgical candidate for knee replacement surgery, or if you still have pain after knee replacement,  your Pain Medicine physician may still be able to provide you with options to improve your pain.  Once such option is ablation of sensory nerves to the knee joint by either cold (cryotherapy) or heat (Radiofrequency lesioning) to  temporarily (6-8 months) damage the sensory nerve from your knee, essentially stopping the pain signal from reaching your central nervous system.   Your doctor can help you determine which treatment is the best for you.