Pain felt on the inner, or medial, side of the knee when bending is a common complaint. This discomfort, aggravated by flexion, suggests that an internal or surrounding structure is being compressed, stretched, or pinched during the bending motion. Understanding the possible sources of this pain, which range from acute structural injuries to chronic inflammatory conditions, is the first step toward finding relief.
Understanding Structural Causes
Pain on the inside of the knee during bending often indicates damage to the stabilizing structures within the joint. Two common acute injuries involve the medial collateral ligament (MCL) and the medial meniscus. The MCL is a broad band of tissue running along the inner side of the knee, providing stability against forces that push the knee inward. When the MCL is sprained or torn, bending the knee stretches the injured tissue, causing sharp pain and tenderness directly along the ligament’s path.
A tear of the medial meniscus, the C-shaped cartilage that acts as a shock absorber, is another frequent cause of pain exacerbated by flexion. Deep knee bending, such as squatting, compresses the meniscal cartilage between the thigh bone (femur) and the shin bone (tibia). If the medial meniscus is torn, this compression can pinch the damaged fragment. This leads to sharp, localized pain on the inner joint line, sometimes accompanied by clicking or catching within the joint.
Identifying Inflammatory Sources
Beyond structural tears, pain can stem from inflammation in the soft tissues surrounding the joint. One common culprit is Pes Anserine Bursitis (PAB), an irritation of the bursa located below the knee joint on the inner side of the tibia. This bursa cushions the insertion of three tendons—the sartorius, gracilis, and semitendinosus—which collectively form the pes anserinus. When the bursa is inflamed, knee flexion causes repetitive friction as these tendons slide over it, leading to pain that worsens with activities like climbing stairs or rising from a chair.
Another inflammatory source is irritation of the medial plica, a fold of the joint lining. If the plica becomes thickened or inflamed due to overuse or minor trauma, it can be caught or impinged between the kneecap (patella) and the thigh bone during bending. This pinching effect creates pain often felt toward the front and inner aspect of the knee, aggravated by repetitive actions like squatting or stair climbing. Additionally, semimembranosus tendinopathy, an inflammation of one of the hamstring tendons on the posteromedial side, causes pain aggravated by deep flexion due to increased friction and loading.
Immediate Steps for Self-Management
Initial management for medial knee pain focuses on symptom reduction and preventing further aggravation. The traditional R.I.C.E. protocol—Rest, Ice, Compression, and Elevation—provides a framework for the first 48 to 72 hours following the onset of significant pain. Rest involves avoiding activities that trigger the pain, which often means limiting deep knee flexion, such as squatting, kneeling, or excessive stair use. If walking is painful, using crutches to temporarily reduce weight-bearing stress on the knee is advisable.
Applying ice to the painful area for about 15 to 20 minutes every couple of hours helps minimize swelling and numbing the pain. Always wrap the ice pack in a thin towel to protect the skin from direct contact. Compression with an elastic bandage helps limit fluid buildup and provides support, but it must be wrapped snugly without causing numbness or increased pain below the knee. Elevating the leg above the level of the heart, particularly when icing, assists in draining excess fluid from the area.
Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, can help manage both pain and inflammation. It is important to take NSAIDs with food to minimize stomach irritation and to avoid them if you have a history of kidney problems, stomach ulcers, or are taking blood thinners. These medications are intended for short-term use, typically not exceeding ten days for pain relief.
When to Consult a Medical Professional
While many cases of medial knee pain improve with self-management, certain warning signs indicate the need for prompt medical evaluation. You should seek immediate attention if you experience an inability to bear weight on the injured leg or if the knee feels unstable, as if it is going to “give out.” A loud popping sound at the moment of injury is a strong indicator of a significant ligament or meniscal tear.
Other concerning symptoms include immediate and severe swelling, visible deformity of the knee joint, or a sensation of the knee “locking” or getting stuck during movement. If the pain is persistent, worsens over time, or does not begin to improve after 48 to 72 hours of dedicated rest and self-care, a medical consultation is necessary to accurately diagnose the source of the pain. Furthermore, if the knee is warm, red, or if you have a fever, this could signal an infection that requires urgent treatment.