The type of arthritis that results from wear and tear over time or overuse of joints is osteoarthritis, which is also called degenerative joint disease and affects more than 30 million Americans. In osteoarthritis of the knee, bones rub directly against bone when cartilage, a connective tissue that provides cushioning and shock absorption within joints, wears away.
Other common forms of arthritis that affect the knees are rheumatoid arthritis and psoriatic arthritis, which are autoimmune conditions that cause widespread joint inflammation and other systemic symptoms throughout the body.
Knee Symptoms
Symptoms of knee arthritis can be intermittent or chronic and progressive in nature, getting worse over time. Knee arthritis can vary in intensity, from mild or moderate symptoms to severe disability that makes everyday tasks and functional movements like standing, walking, squatting, and going up and down stairs very difficult and painful.
Common symptoms of knee arthritis include:
Pain: Joint pain is the most common symptom of knee arthritis that results from breakdown of cartilage in the knee. This lack of protective cushioning and shock absorption from cartilage loss causes the ends of the femur and tibia, the leg bones that form the knee joint, to grind against each other with increased friction. Tenderness: Increased pain and inflammation that results from knee arthritis can cause tenderness surrounding the knee, especially joint line tenderness at the inside and outside portion of the knee joint where the ends of the femur and tibia meet. Stiffness: Cartilage helps provide cushioning within joints that allow bones to glide smoothly on one another. When cartilage breaks down with knee arthritis, the knee joint can stiffen up, especially in the morning upon waking. Knee stiffness typically lasts less than 30-60 minutes with osteoarthritis, but can remain for 60 minutes or more for prolonged periods of time with rheumatoid arthritis. Crepitus: Joint crepitus, or popping, cracking, or grinding sounds with movement of the knee, can occur due to increased joint stiffness. Decreased range of motion: Arthritis of the knee can cause decreased range of motion of the knee joint, often causing difficulty bending the knee, due to increased joint stiffness as well as pain with movement that makes bending the knee uncomfortable. Swelling: Knee arthritis can cause swelling of the knee from inflammation of the knee joint due to increased friction between bones from cartilage degradation. Swelling within the knee joint can also result from inflammatory processes that attack the joints that occur with autoimmune forms of arthritis such as rheumatoid arthritis and psoriatic arthritis. Weakness: Arthritis of the knee can cause weakness in the supporting muscles that surround the knee and hip joints. Because bending the knees and functional movements that require use of the knees such as walking, squatting, and stair climbing can be painful, people with arthritis often avoid these activities, which leads to muscle atrophy and weakness from lack of leg muscle use. If only one knee is affected by arthritis, people will often compensate by placing less weight on the leg with the affected knee, which also leads to muscle weakness from disuse. Gait problems: Due to acquired muscle weakness and decreased weight placed through the legs with arthritic knees, it is common for patients with knee arthritis to demonstrate gait problems affecting their normal ability to walk. Common gait deviations seen in patients with knee arthritis include decreased knee and hip range of motion and weight-bearing that can cause a slow gait speed, shuffling pattern, widened stance, or limping if arthritis only affects one side. Poor balance: Because the surrounding leg muscles of the knee and hip joints often become weak with knee arthritis, it can be difficult to maintain your balance as your legs may lack adequate support and stability from muscle groups like the glutes and quadriceps.
Systemic Symptoms
While osteoarthritis of the knee causes symptoms primarily at just the knee joint, other forms of arthritis, such as autoimmune conditions like rheumatoid arthritis and psoriatic arthritis, can affect the whole body and are often accompanied by systemic symptoms.
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is an autoimmune condition where the immune system attacks the joints, causing pain, inflammation, and swelling. Over time, cartilage within joints breaks down, narrowing the space between bones, and joints can become unstable or stiff. If left untreated, rheumatoid arthritis can cause permanent and irreversible joint damage.
Unlike osteoarthritis, which is more likely to develop on one side of the body, rheumatoid arthritis is usually symmetrical, affecting both sides of the body, and commonly affects the knees. RA is also more likely to affect multiple joints of the body, causing pain, stiffness, swelling, inflammation, warmth, and redness, and can also cause systemic symptoms like fatigue, fever, and weakness. Women are two to three times more likely to be diagnosed with RA than men.
Other systemic symptoms RA may cause include:
NodulesRashesLoss of bone densityScleritis (inflammation of the whites of the eyes)Dryness of the eyes and mouthPulmonary fibrosisAtherosclerosisAnemiaBlood clots
Psoriatic Arthritis
Alternatively, about 30% of patients with psoriasis, an inflammatory condition of the skin, develop an autoimmune, inflammatory form of arthritis called psoriatic arthritis. Psoriatic arthritis can affect the joints of the entire body and result in permanent joint damage if left untreated. Psoriasis affects 7.4 million adults in the United States.
Systemic symptoms of psoriatic arthritis include:
Scaly, itching skin patches Pain and swelling at other joints Chronic fatigue Inflammation of the eyes called uveitis Inflammation of the spine Tendon and ligament pain Muscle pain and weakness Depression Digestive symptoms, such as abdominal pain, bloating, constipation, and diarrhea Organ damage from inflammation to the heart, lungs, or kidneys
When to See a Doctor
If you have been experiencing significant knee pain, stiffness, decreased mobility, or swelling for more than three months that is interfering with your ability to perform everyday tasks, making it uncomfortable to sit, stand, or walk, you should schedule an appointment with a doctor to address your symptoms. Symptoms of arthritis can worsen over time if left untreated.
A Word From Verywell
Arthritis symptoms can vary from mild discomfort to significant disability that can limit everyday activities. It is important that you seek medical attention if you have been experiencing joint pain, stiffness, or swelling for more than three months. Inflammation and degradation of joints can be reduced and prevented if arthritis is diagnosed and managed early. Physical therapy can also help manage your symptoms by improving your joint mobility, range of motion, and strength, as well as teach you activity modifications to lessen strain on painful joints.
