Introduction

Knee pain is a common medical condition experienced by people of all age groups. However, the causes of knee pain may vary according to the age group. For example, children are prone to infections, young adults are prone to injuries, and inflammatory disorders are common among the elderly.

Likewise, the severity of the pain also varies. Some knee pain affects activities of daily living; some pain is mild and affects active lifestyles; and some pain is severe, requiring urgent intervention. The severity also depends on the cause of the knee pain. Whatever the cause may be, it is important for you to seek medical advice if you have knee pain.

In the article, we have explained the six main causes of knee pain.

Injury

Traumatic injury to the knee is very common and can cause damage to ligaments, tendons, cartilage, bones, and bursae (fluid-filled sacs). Common symptoms associated with a knee injury are sudden, severe knee pain and swelling. Some common knee injuries include:

• Sprained or Strained Knee Ligaments: Ligaments are structures connecting the thigh bone with the bones of the lower legs to provide stability to the knee joint, Commonly injured ligaments in the knee joint are the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and medial collateral ligaments (MCL). 

Among them, anterior cruciate ligament tears are common and occur mostly in athletes while sudden turning, sudden stopping, landing incorrectly, or colliding with another person. There is a popping sound after the injury, and the pain is severe. The knee might feel giving away after the injury, and you might also feel unstable while walking.

The treatment usually involves acute pain management and knee stabilization. Sometimes, surgery may be required.

• Torn Cartilage: Menisci are the cartilage present at the knee joint. There are two menisci, medial and lateral, which function as shock absorbers and also provide stability to the knee joint.

Meniscal injuries occur commonly while playing sports when there is a sharp turn or twist. The symptoms associated with it are sudden and severe knee pain, a popping sound during injury, and a feeling of the knee giving away. Menisci injuries are commonly associated with ligament tears. Treatment involves wearing knee braces or having surgery.

• Fractures: There might be fractures of the lower end of the femur, the upper end of the tibia, or the patella during the trauma. People with osteoporosis can sustain fractures even with tibial trauma such as wrong stepping. The pain is severe, and treatment varies according to the severity of the fracture.

• Knee Bursitis: A bursa is a fluid-filled sac in the knee joint that cushions the knee joint for smooth gliding movement of bones. There might be an injury to the bursa resulting in inflammation during knee injuries.

Inflammation

Inflammation of the joint is also known as arthritis. Arthritis of the knee joint is associated with symptoms such as pain, swelling, and stiffness of the knee joint. Some common conditions associated with the inflammation of the knee joint are

• Osteoarthritis: It is the most common form of arthritis. As age increases, there is a progressive wearing of the cartilage, and the bones slide against each other during movement, causing pain. The condition is common among the elderly and is progressive.

Some risk factors for osteoarthritis are increasing age, obesity, infection, genetics, injuries, and certain occupations like construction workers. Progressive pain, swelling, stiffness, reduced range of movement, weakness, and deformity are the common symptoms associated with osteoarthritis. The treatment involves pain management and physiotherapy.

• Rheumatoid Arthritis: It is an autoimmune condition that can affect any joint in the body, causing inflammation, including the knee joint. The condition is debilitating and can cause symptoms such as pain, swelling, morning stiffness, and deformity. The symptoms can be intermittent, as opposed to the progressive nature of osteoarthritis.

The treatment is done with disease-modifying anti-rheumatoid drugs (DMARDS), NSAIDs, and steroids.

• Gout: It is a condition associated with increased uric acid in the blood, which is deposited in the joints in the form of crystals, resulting in joint inflammation. The most common joint involved is the big toe, but the knee joint might also be involved. The symptoms of gout are joint pain, swelling, redness, stiffness, and decreased range of motion.

• Pseudogout: The condition is similar to gout but the crystals deposited are calcium crystals and the knee joint is commonly involved, as opposed to the big toe in gout. Symptoms are also similar to those of gout.

• Patellar tendinitis: The patellar tendon is a thick fibrous tissue that connects the patella to the shin bone and helps in various activities involving the knee joint. The inflammation of the patellar tendon is called patellar tendinitis. Inflammation is common in people involved in jumping activities such as runners, cyclists, skiers, and athletes. Common symptoms associated with patellar tendinitis are pain and stiffness.

Infections

Septic arthritis can be defined as an infection of joint tissues by bacteria, viruses, or fungi, and it can also involve the knee joint. The condition is more common in children. The infectious agent may colonize joint fluids via the bloodstream, or skin surrounding the joints.

The risk factors of septic arthritis are:

• Intravenous drug use
• Chronic diseases such as lung disease or kidney disease.
• A suppressed immune system like diabetics, people taking steroids, HIV infection
• Inflammatory joint diseases like osteoarthritis, and rheumatoid arthritis.
• Bloodborne infection

The symptoms associated with the condition are fever, joint pain, and joint swelling. The condition can be treated with early intravenous antibiotics and surgery for pus drainage.

Mechanical Problems

• Loose body: Cartilages and bone in the knee joint can break off due to degeneration, and the broken tissue can float in the joint fluid in the form of loose bodies. Although it usually does not induce inflammation, loose bodies can cause pain and restriction of joint motion,

• Iliotibial band syndrome: There is a tough band of tissue running from the hip bone to the knee joint. Sometimes, this tissue can get tightened, causing pain in the thigh and knee joints. The condition is common among long-distance runners and cyclists.

• Dislocated Knee Cap: following injury or trauma, there can be a dislocation of the knee cap (patella), and it slips out of its place, causing knee pain and stiffness.

• Hip or Foot Pain: When there is a pain in the hip or foot due to a certain condition, you might change your gait to reduce the pain. This change in gait can put more stress on the knee joint, resulting in pain.

Cancer

One of the causes of knee pain is cancer of the joint. Cancer of the joint can also be associated with joint swelling, limping, problems moving around, weakened bone leading to bone fracture, and systemic symptoms such as unintentional weight loss and fatigue.

Cancer may arise from the bone or can be metastatic cancer spreading from other sites. The treatment of bone cancer depends on the type of cancer and the extent of cancer spread. The main modalities of treatment are surgery, chemotherapy, and radiotherapy.

Common cancers affecting the knee joints are: 

• Chondrosarcoma: It is a tumor of the cartilage cells, causing symptoms such as swelling due to bone mass and progressive pain, worse at night, which is relieved by taking NSAIDs.
• Osteosarcoma: It occurs often in the knee region and involves bone-producing cells.
• Giant cell tumor: It is also common in the knee area. It is a locally aggressive benign tumor.

Patellofemoral Pain Syndrome

It is also known as a runner’s knee associated with pain over the knee joint. As the name suggests, it is commonly seen in people with a certain way of walking or running. Other common risks of runner’s knee include:

• Structural defects
• Weak thigh muscles and tight hamstrings
• Tight Achilles tendon.
• Overuse of the knee joint
• Knee injury
• Too high a patella in the knee joint.

The symptoms associated with the patellofemoral syndrome are:

• Pain after activity or pain after bending the knee for a long time while sitting
• Rubbing, grinding, or clicking sounds of the knee joint while straightening the bent knee.
• Tender patella.

The treatment for the runner’s knee is to stop running unless you are pain-free. Meanwhile, you can take advice from physiotherapy for stretching and strengthening exercises. Additionally, pain can be managed by applying ice packs, elevating legs, applying compression, and taking pain medications.

Conclusion

Knee pain is a common health condition affecting people’s mobility and quality of life in all age groups. There are multiple causes of knee pain, including injuries, infections, inflammation, mechanical causes, cancers, and others. The causes of knee pain vary according to age groups and people’s physical activity.

Although the causes of knee pain are multiple, you need to see your doctor whenever you have knee pain and follow your doctor’s advice. Sometimes there is no permanent treatment for the underlying cause of the knee pain. In such conditions, there are appropriate options available to relieve your pain so that you do not have to live with the pain and be able to live your life without compromising its quality.

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