Deciphering Knee Pain

As a physical therapist, our job is to figure out what is causing your pain/problem and then determine/teach you how to fix it. Low back pain and knee pain are probably the two most common diagnoses we see. Neck pain and shoulder pain are next on the list. We combine information such as the cause of the injury, the description of the pain, and the results from our examination to come up with a plan. Today we are going to focus on some factors to help diagnosis pain in the knee.

The knee is basic in terms of it's movement compared to other joints. The knee primarily bends and straightens, where as other joints such as the hip and shoulder are more complex because they also rotate. Despite having simple mechanics, the knee is comprised of multiple structures. Here is a diagram showing the anatomy of the front of the knee:

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Since there are so many structures, the the specific location of an individual's knee pain can be very revealing. No two cases are the same and everyone presents with different factors to consider, but determining where the exact pain is gives a lot of information. Here is a diagram showing possible diagnoses for different pain regions:

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  • Pain above the knee cap (red): This typically means quad tendonitis because this is where the quad muscles come down and turn into a tendon before crossing over the knee. The quads may be overused, weak, and/or inflexible. 
  • Pain around the knee cap (orange): This typically means patella femoral pain syndrome (also known as runners knee), which is a diagnosis that refers to poor movement of the kneecap. When you bend and straighten your knee, the kneecap should slide through a groove in the femur. If it slides out of this groove, the result is typically pain. This can be do to alignment issues or muscle imbalances including weakness or flexibility problems. 
  • Pain below the knee cap (green): This is most often due to patella tendonitis, often referred to as "jumper's knee" because the tendon is used when jumping. It is also seen in runners. The tendon below the kneecap may be overused, weak, or inflexible. 
  • Pain on the outside of the knee (purple): This is often due to a tight IT band, which starts at the hip and comes down to attach at the outside of the lower knee. IT band syndrome can be from weak hips (primarily glutes), muscle imbalances, and/or inflexibility. 
  • Pain on the inside of the knee (red): This may be due to pes anserine bursitis. Three large muscles (sartorius, gracillis, and semitendonosis) come down from the hip and attach at this site. Overuse and/or inflexibility of these muscles results in rubbing and pulling causing bursitis. 
  • Pain on the outside or inside of the knee along the joint line (yellow): This may be due to a meniscus injury including either a traumatic or degenerative tear. 
  • Pain under the knee on the top of the tibia/shin bone (blue): This is often due to Osgood-Schlatter disease, which is most commonly see in active growing kids involved in sports with lots of running and jumping. Extra stress is placed on the site where the patella tendon attaches and pain results. This problem typically resolves with time, but strengthening and stretching can help. 
  • Pain following trauma to the knee: Depending on the type and extent of the trauma, there may be a ligament/tendon tear(s) or a fracture/broken bone(s). If the pain is severe enough, imaging may be completed. A less severe trauma may simply mean a muscle strain or ligament sprain has occurred.
  • Pain in any region: Arthritis or cartilage damage can provoke pain throughout the knee. Strengthening and flexibility exercises are often helpful, but imaging may be needed for further information.
  • Pain in the back of the knee (not shown): This is less common, but still important to consider. Hamstring tendonitis often causes pain where the hamstrings attach in the back of the knee. Baker's cysts may also cause pain in the back of the knee and are typically identified by lots of fluid build up. 

Note: There are many other causes of pain in the knee including stress fractures, nerve pain and referred pain from other areas of the body such as the low back. This list is not all inclusive!

Have you ever had knee pain? What was the diagnosis?