Pain experienced on the inner side of the knee, known as medial knee pain, is a very common complaint. This discomfort can arise from sudden injuries or long-term wear and tear, due to the intricate anatomy of the knee joint. The knee is a complex hinge joint where the thigh bone meets the shin bone, stabilized by a network of ligaments, cushioned by cartilage, and supported by various tendons and fluid-filled sacs. Pinpointing the precise cause of medial pain requires understanding the unique symptoms associated with different underlying conditions.
Acute Injuries to Ligaments and Cartilage
Sudden, intense pain on the inside of the knee often points to a traumatic injury affecting the stabilizing structures. The Medial Collateral Ligament (MCL) is a thick band of tissue running along the inner knee that prevents the joint from buckling inward. An injury to the MCL, typically a sprain or tear, commonly occurs from a direct blow to the outside of the knee or a forceful, sudden twisting motion while the foot is planted.
Symptoms of an MCL injury include immediate sharp pain, tenderness along the inner edge of the knee, and a feeling of instability. Depending on the severity of the tear, swelling may appear immediately or develop over the next day or two, and a popping sound may be heard at the moment of injury.
Another frequent source of acute medial pain is a tear of the medial meniscus, the C-shaped cartilage that acts as a shock absorber and stabilizer. This injury often results from a twisting movement, especially when the knee is bent, such as when squatting or pivoting during sports.
Specific symptoms of a medial meniscus tear include mechanical issues like catching, clicking, or the knee locking. Locking is the inability to fully straighten the leg due to torn cartilage blocking the joint. Pain is typically felt directly along the joint line on the inside of the knee and worsens with activities that involve rotation or deep squatting. Although swelling may not be immediate, it commonly increases gradually over 24 to 48 hours following the initial traumatic event.
Overuse Syndromes and Localized Inflammation
Pain that develops gradually, often related to repetitive activity, may indicate an overuse syndrome involving soft tissues below the joint line. A distinct cause of pain in this area is Pes Anserine Bursitis, which involves the inflammation of a fluid-filled sac called the pes anserine bursa. This bursa is located approximately two inches below the knee joint on the inner side of the shin bone, underneath the combined tendons of three hamstring muscles.
The mechanism of irritation is typically repetitive friction or pressure from the overlying tendons, often triggered by activities like running, cycling, or excessive hill climbing. Tight hamstring muscles, obesity, or concurrent knee osteoarthritis can increase a person’s susceptibility to this condition.
The resulting pain is highly localized to a specific point below the joint line and is tender to the touch, distinguishing it from pain originating inside the joint itself. Symptoms are often aggravated when rising from a seated position, climbing stairs, or attempting to sleep with the knees touching. The condition is a common source of medial knee discomfort, especially in middle-aged women and athletes.
Chronic Pain from Joint Degeneration
When medial knee pain develops slowly over months or years, worsening over time, the underlying issue is frequently Medial Compartment Osteoarthritis (OA). This is a degenerative joint condition where the protective articular cartilage on the ends of the bones gradually wears away. It is the most common form of knee arthritis, often starting in the medial compartment because that side bears the majority of the body’s weight during movement.
As the cartilage deteriorates, the cushioning effect is lost, leading to bone-on-bone friction that triggers pain and inflammation. Early symptoms include stiffness, which is most noticeable in the morning or after periods of rest. The pain gradually increases with prolonged weight-bearing activities and can be accompanied by a grating or crunching sensation, known as crepitus, when the joint moves.
This progressive condition leads to a gradual loss of mobility and a reduced ability to fully straighten the knee. Risk factors such as advanced age, a history of knee injury, and obesity can accelerate the deterioration of the medial compartment cartilage.
Next Steps for Diagnosis and Relief
When pain on the inside of the knee significantly affects daily function, seeking medical evaluation is the next step. A doctor will perform a physical examination to test the stability of the ligaments, check for tenderness at specific points, and assess the knee’s range of motion. The physical examination is often the primary tool for distinguishing between a ligament sprain, a meniscal tear, or bursitis.
Imaging studies are often used to confirm a diagnosis or rule out other possibilities. X-rays can show the extent of joint space narrowing and bone spur formation associated with osteoarthritis. A Magnetic Resonance Imaging (MRI) scan provides detailed images of soft tissues like the ligaments, tendons, and menisci.
For immediate relief before a full diagnosis, the RICE protocol is recommended: Rest, Ice, Compression, and Elevation. It is important to seek immediate medical attention if you experience:
- Severe swelling
- An inability to bear any weight on the leg
- An obvious deformity
- Pain that does not begin to improve after 48 hours of consistent rest and icing