18 Surprising Reasons Your Knees Are Bothering You

9. Osteoarthritis

Osteoarthritis, the most common form of arthritis, is the result of joint damage. Joint damage accumulates, which is why age is a significant risk factor for osteoarthritis. Individuals can develop joint damage due to ligament injuries, torn cartilage, obesity, repetitive stress on the joint, and bone deformities. Osteoarthritis can occur in many joints, though it is most common in the hands, hips, and knees. It is when it occurs in the knees that it can cause knee pain. Symptoms of osteoarthritis, aside from joint pain, include joint stiffness, bone spurs, joint swelling, grating sensation, clicking sensation, joint tenderness, and a loss of flexibility in the affected joint. Unfortunately, there is no cure for osteoarthritis. However, there are effective treatments that reduce pain and make other symptoms more manageable. These treatments include anti-inflammatories, pain medication, cortisone injections, physical therapy, joint replacement, and joint realignment surgery.

10. Osgood-Schlatter Disease

Osgood-Schlatter disease is a major condition that involves inflammation of the patellar tendon, which is what attaches the kneecap to the shinbone. This disease is a common trigger for knee pain in adolescents. In most cases, Osgood-Schlatter disease occurs when children and adolescents are going through growth spurts, often during puberty. This is a time when their tendons, muscles, and other body parts are rapidly changing, putting more stress on their body, including their knees and surrounding area. Physical activities and sports put adolescents at a particularly high risk of this condition. This is because running, jumping, and bending cause the quadriceps to pull on the patellar tendons. The repetitive stress causes this tendon to pull on the growth plate around the shinbone. Over time, this triggers pain and swelling in and around the knees. Thankfully, Osgood-Schlatter disease often heals over time, typically when an adolescent stops growing. However, treatment options are available when needed. They include pain medication, such as ibuprofen, cold compresses, rest, physical therapy, and surgery.

11. Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that affects the joints, including the knees. The immune system mistakenly attacks the joint lining, causing inflammation, pain, and swelling. Over time, RA can lead to joint damage and deformity. Unlike osteoarthritis, which develops from wear and tear, RA often affects both knees symmetrically. Common symptoms include stiffness, especially in the morning, redness, and warmth around the joint. Flares of RA can worsen pain and reduce mobility. Treatment typically involves disease-modifying antirheumatic drugs (DMARDs) and biologics to slow disease progression, along with anti-inflammatories, physical therapy, and lifestyle modifications.

12. Gout

Gout is a form of inflammatory arthritis caused by the buildup of uric acid crystals in the joints. Although it most commonly affects the big toe, gout can also cause intense knee pain. A gout attack in the knee can lead to sudden, severe pain, swelling, redness, and warmth. Triggers include consuming high-purine foods (like red meat and shellfish), alcohol, and dehydration. Treatment focuses on reducing inflammation with medications such as colchicine, corticosteroids, and nonsteroidal anti-inflammatory drugs (NSAIDs). Long-term management includes dietary changes and medications to lower uric acid levels.

13. Baker’s Cyst

A Baker’s cyst, also known as a popliteal cyst, is a fluid-filled sac that forms at the back of the knee. It often develops due to excess joint fluid from arthritis or a knee injury. Symptoms include swelling behind the knee, stiffness, and discomfort when fully bending or straightening the leg. In some cases, a Baker’s cyst can rupture, causing sharp pain and bruising in the calf. While small cysts may resolve on their own, larger ones may require drainage, corticosteroid injections, or treatment of the underlying condition contributing to fluid buildup.

14. Patellofemoral Pain Syndrome (Runner’s Knee)

Patellofemoral pain syndrome, commonly called runner’s knee, is a frequent cause of knee pain, especially in athletes and active individuals. It results from irritation of the cartilage under the kneecap due to overuse, improper kneecap alignment, or muscle imbalances. Symptoms include dull, aching pain around the kneecap, particularly when climbing stairs, squatting, or sitting for long periods. Treatment typically includes physical therapy, strengthening exercises, rest, and proper footwear. Orthotic inserts or taping may help correct misalignment and prevent further pain.

15. Chondromalacia Patella

Chondromalacia patella occurs when the cartilage under the kneecap softens and deteriorates, leading to pain and inflammation. This condition is common among young athletes, older adults with arthritis, and individuals with misaligned kneecaps. Symptoms include knee pain that worsens with activity, stiffness, and a grinding sensation when moving the joint. Treatment involves rest, physical therapy, anti-inflammatory medications, and exercises to strengthen the surrounding muscles and improve patellar alignment. Severe cases may require surgical intervention.

16. Fractures

Fractures in the knee can occur from direct trauma, falls, or high-impact injuries. The patella (kneecap), tibia, or femur may fracture, causing severe pain, swelling, bruising, and difficulty moving the leg. A knee fracture requires immediate medical attention, and treatment depends on the severity of the break. Non-displaced fractures may heal with immobilization in a brace or cast, while more complex fractures often require surgical repair with plates, screws, or rods. Physical therapy is crucial in regaining mobility after healing.

17. Septic Arthritis

Septic arthritis is a bacterial or fungal infection that affects the knee joint, causing severe pain, swelling, warmth, and redness. This condition requires urgent medical attention, as it can rapidly destroy joint tissue if left untreated. Common causes include infections spreading from other parts of the body or direct contamination from a knee injury or surgery. Doctors diagnose septic arthritis through blood tests and joint fluid analysis. Treatment involves hospitalization, intravenous antibiotics, and sometimes joint drainage to remove infected fluid.

18. Peripheral Artery Disease (PAD)

Peripheral artery disease occurs when narrowed arteries reduce blood flow to the legs, leading to knee pain, cramping, and weakness—especially during physical activity. PAD is commonly caused by atherosclerosis, where fatty deposits build up in the arteries. Other risk factors include smoking, diabetes, high blood pressure, and high cholesterol. Symptoms often improve with rest but can progress to persistent pain if circulation worsens. Treatment includes lifestyle modifications, medications to improve blood flow, and, in severe cases, angioplasty or surgery to restore circulation.