Side knee pain affects people across all activity levels. This discomfort often originates from structures like ligaments, cartilage, or tendons that stabilize the complex knee joint. Understanding the precise location of the pain is the first step toward identifying the underlying cause and finding effective relief. Distinguishing between pain on the inner side and pain on the outer side significantly narrows down the potential issues.
Differentiating Inner and Outer Knee Pain
The knee is anatomically divided into compartments, described using the terms medial (inner) and lateral (outer). Medial knee pain is felt on the inner side of the joint, closest to the opposite leg. This inner compartment contains structures often injured when the knee is forced inward or twisted. Lateral knee pain is felt on the outer side, away from the other leg. Pinpointing the exact location and sensation helps healthcare professionals determine which specific structure may be involved.
Common Causes of Inner (Medial) Knee Pain
The inner side of the knee is stabilized by the Medial Collateral Ligament (MCL). An MCL injury, typically a sprain or tear, often results from a direct blow to the outside of the knee that forces the joint inward, or from a sudden twisting motion. Pain from an MCL injury is usually felt directly over the ligament itself and can range from tenderness to sharp pain, accompanied by a feeling of instability in more severe cases.
Another frequent source of inner knee pain is a tear in the medial meniscus, one of the two C-shaped pieces of cartilage that act as shock absorbers. Tears can occur acutely from a forceful twist while the foot is planted, or they can develop gradually due to degenerative wear. This injury is characterized by pain along the joint line, and may involve mechanical symptoms like clicking, catching, or a sensation that the knee is locking up.
Pain felt slightly below the knee joint line may point to Pes Anserine Bursitis, which is inflammation of the bursa located beneath the hamstring tendons. This condition is an overuse injury, often seen in runners or individuals with tight hamstrings. The pain is typically a dull ache that worsens with activity, particularly with climbing stairs or rising from a chair.
Common Causes of Outer (Lateral) Knee Pain
The most common cause of pain on the outer side of the knee is Iliotibial Band Friction Syndrome (ITBS), prevalent among distance runners and cyclists. The iliotibial band is a thick strip of connective tissue that runs from the hip down the outside of the thigh to the knee. Repetitive bending and straightening of the knee can cause the band to rub over the lateral femoral condyle, leading to inflammation and a characteristic burning pain.
A Lateral Collateral Ligament (LCL) injury is typically caused by a direct impact to the inside of the knee, stretching the outer ligament. The LCL connects the thigh bone to the fibula and stabilizes the outer knee. A sprain or tear results in pain, swelling, and tenderness directly over the outer side of the joint, often accompanied by instability.
A tear in the lateral meniscus, the shock-absorbing cartilage on the outer side, is another potential cause of lateral pain. This injury can result from a sudden twisting motion or from gradual degeneration. Pain is focused along the outer joint line and may be associated with mechanical symptoms such as clicking or a feeling that the knee is giving way.
Immediate Care and When to See a Doctor
For immediate self-care following a minor knee injury, the R.I.C.E. methodology is widely recommended to manage initial symptoms. Rest involves avoiding activities that place stress on the knee. Ice should be applied to the painful area for 10 to 20 minutes several times a day to reduce swelling and inflammation. Compression, using an elastic bandage, helps minimize fluid buildup, but the wrap should be snug without causing numbness. Elevation means propping the injured leg up above the level of the heart to drain excess fluid. Over-the-counter NSAIDs like ibuprofen can also help manage pain and inflammation in the short term.
It is important to seek professional medical attention if “red flag” symptoms are present, as they may indicate a more serious injury requiring specific treatment. These warning signs include:
- Inability to bear weight on the injured leg.
- A noticeable deformity around the joint.
- Severe, unmanageable pain.
- A knee that locks or catches.
- A feeling of significant instability.
- Signs of infection such as redness, warmth, or a fever.