Understanding what is causing your knee pain may be a simple task, or more complicated. A skilled physician can use clues to determine the cause of knee pain. Some of these clues have to do with you (how old are you? What types of activities do you do?), and some with your symptoms (has your knee pain been ongoing? Was there a recent injury?).
Here are some of the common knee pain symptoms that are experienced by patients, and what these symptoms may mean about the cause of your knee pain.
Location of Pain:
- Front of Knee: Pain over the front of the knee is most commonly related to the knee cap. Kneecap pain can be caused by several different problems.
- Inside of Knee: Pain on the inside, or medial side, of the knee is commonly caused by medial meniscus tears, MCL injuries, and arthritis.
- Outside of Knee: Pain on the outside of the knee, or lateral side, is commonly caused by lateral meniscus tears, LCL injuries, IT band tendonitis, and arthritis.
- Back of Knee: Pain in the back of the knee can be due to the collection of fluid, called a Baker's Cyst.
Timing of Pain:
- While going down stairs: Pain while walking down steps is very commonly associated with kneecap problems, such as chondromalacia.
- Morning pain: Pain after first waking in the morning that quickly resolves with gentle activity is typical of early arthritis.
Swelling of the knee is common with several different knee problems. When there is an effusion immediately after a knee injury, a possible cause is severe injury to an internal joint structure, like the anterior cruciate ligament or a fracture of the top of the shin bone.
When swelling develops gradually over hours to days after an injury, it is likely to be something less severe, like a tear of the meniscus or a ligament sprain.
Mobility of the knee can be affected by a number of common conditions. If mobility is chronically limited, often the cause is arthritis. When the surface of the joint becomes irregular as a result of the arthritis, the mobility of the joint may become limited.
If the mobility is limited after an acute injury, there is likely swelling limiting the motion, or a torn structure that is limiting the mobility.
The stability of the knee is provided by the ligaments that connect the shin bone (tibia) to the thigh bone (femur). When the ligaments are stretched or torn, the knee may feel as though it is giving way beneath the patient. A sensation that the knee may give out from beneath you is a common symptom of ligament injury.
Popping and snapping within the knee is common, and often not a symptom of any particular problem. When the pops are painless, there is usually no problem, but painful pops and snaps should be evaluated by your doctor. A pop is often heard or felt during an injury when a ligament, such as the ACL, is torn.
Grinding or crunching is a common symptom of cartilage problems. If the cartilage is damaged -- a condition called chondromalacia -- a crunching sensation is often felt by placing the hand over the kneecap and bending the knee. A similar grinding sensation may be felt with knee arthritis.
Locking is a symptom that occurs when a patient cannot bend or straighten their knee. The locking can either be due to something physically blocking motion of the knee, or by pain preventing normal knee motion.
One way to determine if there is something physically blocking knee motion is to inject the knee with a numbing medication. After the medication has taken effect, you can attempt to bend the knee to determine if pain was blocking the motion or if there is a structure, such as a torn meniscus, that is blocking normal motion.
Examining the Knee:
Determining the cause of knee pain relies on a proper examination of the knee joint. Learn about how your doctor can examine your knee to determine the source of your pain, and what tests can be performed to make the diagnosis.
Browne K, Kurtz CA. "How to perform a comprehensive examination of the knee" JAAPA. 2009 Jun;22(6):20-5.