Medial compartment osteoarthritis involves the knee joint, whereby the cushioning layer between your knee bones deteriorates over time. Deterioration of this cushion layer, also known as cartilage, results in your knee bones rubbing together. Over time, this leads to knee pain, knee joint stiffness and swelling [source: FamilyDoctor.org]. Osteoarthritis of the knee is the most common type of osteoarthritis. It can lead to difficulties with simply daily tasks, like walking, going up stairs, running, jumping, and getting in and out of chairs. As a result, moderate to severe medial compartment osteoarthritis can lead to disability [source: NIAMS].

The medial meniscus of the knee is a cartilage pad between the thigh bone (the femur) and the shin bone (the tibia). A healthy medial meniscus is smooth and allows the bones to glide without friction. The meniscus cartilage also absorbs shock from movement [source: NIAMS]. A knee with medial compartment osteoarthritis has a worn or even nonexistent medial meniscus, resulting in friction between the femur and tibia whenever you move or bend your knee. Over time, damage to the joint can result in knee malformation. There may also be small bone deposits around the knee joint, known as osteophytes or bone spurs [source: NIAMS].

There are several risk factors for developing medial compartment osteoarthritis, including genetics, age, and biological and environmental factors. In particular, previous knee injury or continuous exertion on the knee may predispose you to medial compartment osteoarthritis later in life. People who engage in manual labor or high-impact sports, for example, are at increased risk of developing medial compartment osteoarthritis. Obesity is another important risk factor. Excess weight puts extra pressure on your knees, leading to greater wear and tear of the cartilage over time. Finally, depleted estrogen levels in women following menopause is another risk factor for developing medial compartment osteoarthritis [source:Arthritis-treatment-and-relief.com].