Knee pain, a common complaint, can significantly affect daily activities. When discomfort localizes to the inner (medial) side of the knee, it often points to issues with structures in that region. Understanding the potential origins of this pain is important for effective treatment.
Key Anatomy of the Inner Knee
The medial collateral ligament (MCL) is a broad, flat band of connective tissue on the inner side of the knee joint. It connects the thigh bone (femur) to the shinbone (tibia) and primarily resists forces that would push the knee inward, maintaining joint stability.
Within the knee joint, the medial meniscus is a C-shaped fibrocartilage structure. It functions as a shock absorber, reducing contact area between the bones and distributing load during movement. The medial meniscus is more firmly attached to the joint capsule and the MCL, which limits its mobility.
Further down on the inner knee, the pes anserine bursa is a fluid-filled sac located beneath the tendons of three muscles. This bursa acts as a cushion, reducing friction where these tendons glide over the shinbone. The medial compartment of the tibiofemoral joint also refers to the inner portion of the knee where the ends of the thigh bone and shinbone meet.
Common Causes of Medial Knee Pain
Pain on the inner side of the knee can stem from several distinct conditions. Each affects the structures previously described, leading to discomfort.
Medial Collateral Ligament (MCL) Injuries
MCL injuries involve stretching or tearing of the medial collateral ligament. These injuries commonly result from a valgus stress, a force applied to the outside of the knee that pushes it inward. This can occur from a direct blow to the outer knee or lower thigh, or from twisting motions, especially in sports like football, soccer, or skiing. The ligament can be stretched (Grade 1 sprain), partially torn (Grade 2), or completely ruptured (Grade 3).
Medial Meniscus Tears
A medial meniscus tear involves damage to the C-shaped cartilage that cushions the inner knee joint. These tears often occur when the knee is suddenly twisted while the foot is planted on the ground. Squatting deeply or engaging in pivoting activities can also contribute to meniscal tears. Degenerative changes in the meniscus due to aging can lead to tears from even minor movements, such as an awkward turn when getting out of a chair.
Pes Anserine Bursitis
Pes anserine bursitis is an inflammatory condition affecting the bursa located on the inner side of the knee, approximately 2 to 3 inches below the joint line. This inflammation often arises from repetitive stress or overuse, such as from activities involving frequent knee flexion and adduction. Tight hamstring muscles are a common contributing factor, as they can exert excessive pressure on the bursa. Direct trauma to the area can also lead to inflammation of this bursa.
Medial Compartment Osteoarthritis
Medial compartment osteoarthritis is a degenerative condition characterized by the gradual breakdown of the protective cartilage in the inner part of the knee joint. As the cartilage wears away, the bones within the joint can rub against each other, leading to pain and inflammation. This condition is often age-related, with normal wear and tear contributing to its development, particularly after age 50. Previous knee injuries, repetitive motions, or conditions like obesity can also accelerate the progression of medial compartment osteoarthritis.
Recognizing Specific Symptoms and When to Seek Medical Care
Each cause of medial knee pain presents with a distinct set of symptoms, though some overlap can occur. Recognizing these indicators helps in understanding the discomfort and determining when medical evaluation is advisable.
For an MCL injury, pain and tenderness are typically felt directly over the ligament on the inside of the knee. Swelling around the knee joint and a feeling of instability, as if the knee might give way, are common. A popping sensation might be heard or felt at the moment of injury, and difficulty bending the knee due to stiffness and pain can occur.
A medial meniscus tear often presents with pain on the inside of the knee joint, which may worsen with twisting or squatting movements. Swelling and stiffness in the knee can develop gradually over a few days. A characteristic symptom is a catching or locking sensation in the knee, where a piece of torn cartilage can interfere with joint movement, potentially preventing full extension.
Pes anserine bursitis typically causes pain and tenderness over the inner knee, about 2 to 3 inches below the joint line. This pain may develop gradually and often increases with activities like climbing stairs, walking, or standing up from a chair. Localized swelling and tenderness to the touch in the affected area are common.
Medial compartment osteoarthritis symptoms usually develop slowly and worsen over time. Pain in the inner knee is common, especially during or after activity, and morning stiffness that improves within about 30 minutes of movement can be experienced. A grating sensation or sound (crepitus) when moving the knee, along with occasional swelling and tenderness, may be present.
It is advisable to seek medical attention if knee pain is persistent, severe, or significantly impacts daily activities. Sudden onset of pain after an injury, noticeable swelling, inability to bear weight, or a feeling of instability or the knee “giving out” are all reasons to consult a healthcare professional. Progressive worsening of symptoms, even without an acute injury, warrants medical evaluation to determine the underlying cause and appropriate management.