Stiff Knees: Causes, Symptoms, and When to Seek Help

What causes stiff knees?

Knee stiffness, characterized by a restricted range of motion and difficulty bending or straightening the joint, is a common complaint stemming from a variety of causes ranging from acute injuries and inflammatory conditions to chronic degenerative changes and lifestyle factors.

Understanding Knee Stiffness

Knee stiffness refers to a sensation of tightness or limitation in the knee joint's movement. It can manifest as difficulty initiating movement after rest (often termed "gelling"), a reduced ability to fully extend or flex the leg, or a general feeling of rigidity. While sometimes a minor inconvenience, it can significantly impact mobility, exercise performance, and quality of life. The knee joint, a complex hinge joint, relies on the smooth interaction of bones (femur, tibia, patella), cartilage, ligaments, tendons, and synovial fluid. Disruption to any of these components can lead to stiffness.

Common Causes of Knee Stiffness

The origins of knee stiffness are diverse and can often be categorized by their underlying pathology:

Degenerative Conditions

• Osteoarthritis (OA): This is by far the most prevalent cause of chronic knee stiffness, particularly in older adults. OA is a "wear and tear" condition where the protective articular cartilage that cushions the ends of the bones gradually breaks down. This leads to bone-on-bone friction, inflammation, and the formation of bone spurs (osteophytes), all of which limit joint movement and cause stiffness, often worse after periods of inactivity (e.g., morning stiffness).

Inflammatory Conditions

• Rheumatoid Arthritis (RA): An autoimmune disease where the body's immune system mistakenly attacks the synovium, the lining of the joints. This results in chronic inflammation, pain, swelling, and significant stiffness, often affecting both knees symmetrically and typically worse in the morning.
• Bursitis: Inflammation of the bursae, small fluid-filled sacs that cushion tendons, muscles, and bones around the joints. In the knee, bursitis (e.g., prepatellar, anserine) can cause localized pain, swelling, and stiffness, especially with movement or direct pressure.
• Tendinitis/Tendinopathy: Inflammation or degeneration of the tendons surrounding the knee (e.g., patellar tendinitis, quadriceps tendinitis). Overuse or repetitive strain can lead to micro-tears and inflammation, causing pain and stiffness, particularly during or after activity.
• Gout and Pseudogout: These conditions involve the accumulation of crystals within the joint space (uric acid crystals in gout, calcium pyrophosphate dihydrate crystals in pseudogout). This triggers severe, acute inflammatory attacks characterized by intense pain, swelling, redness, and profound stiffness, often affecting a single joint.
• Psoriatic Arthritis: A form of arthritis that affects some people with psoriasis. It can cause inflammation, pain, and stiffness in various joints, including the knees.

Acute Injuries

• Meniscus Tears: The menisci are C-shaped pieces of cartilage that act as shock absorbers and stabilizers within the knee. Tears can cause pain, swelling, and a sensation of locking or catching, which limits movement and leads to stiffness.
• Ligament Sprains: Injuries to the major knee ligaments (ACL, PCL, MCL, LCL) can result from sudden twists, impacts, or hyperextension. Swelling, instability, and pain following a sprain often lead to significant stiffness and a reduced range of motion.
• Fractures: A break in any of the bones forming the knee joint (femur, tibia, patella) can cause severe pain, swelling, and immediate stiffness due to trauma and the body's protective response. Immobilization during healing also contributes to stiffness.
• Contusions: Direct impact to the knee can cause deep bruising, leading to swelling and pain that restricts movement and causes temporary stiffness.

Overuse and Repetitive Strain Injuries

• Patellofemoral Pain Syndrome (PFPS): Often called "runner's knee," this condition involves pain around or behind the kneecap. It's often due to imbalances in the muscles surrounding the knee or poor patellar tracking, leading to irritation and stiffness, especially after prolonged sitting or during activities like climbing stairs.
• Iliotibial Band (ITB) Syndrome: Inflammation of the IT band, a thick band of connective tissue running along the outside of the thigh from the hip to the tibia. Repetitive friction over the lateral femoral condyle can cause pain and stiffness on the outer aspect of the knee.

Other Factors and Conditions

• Lack of Movement/Immobility: Prolonged periods of inactivity, such as after surgery, bed rest, or a sedentary lifestyle, can lead to joint stiffness. Synovial fluid, which lubricates the joint, becomes less effective without movement, and surrounding tissues can shorten and lose elasticity.
• Obesity: Excess body weight places increased stress on the knee joints, accelerating wear and tear. Adipose tissue also produces inflammatory mediators, contributing to systemic inflammation that can worsen joint symptoms.
• Age: As we age, cartilage naturally thins, and tissues can become less elastic, contributing to a general increase in joint stiffness.
• Infection (Septic Arthritis): A bacterial or fungal infection within the joint space is a medical emergency. It causes rapid onset of severe pain, swelling, redness, warmth, and profound stiffness, often accompanied by fever and chills.
• Baker's Cyst (Popliteal Cyst): A fluid-filled sac that forms behind the knee, often secondary to other knee conditions like arthritis or meniscus tears. While usually benign, a large cyst can cause a feeling of tightness, pressure, and stiffness, especially with full knee flexion.
• Post-Surgical Adhesions: Following knee surgery, scar tissue (adhesions) can form, limiting the joint's range of motion and causing persistent stiffness.

When to Seek Medical Attention

While mild, temporary stiffness might resolve with rest and conservative measures, it's crucial to consult a healthcare professional if knee stiffness is:

• Sudden and severe.
• Accompanied by significant pain, swelling, redness, or warmth.
• Associated with fever or chills.
• Follows a specific injury.
• Causes a "locking" or "giving way" sensation.
• Progressively worsening or persistent despite self-care.
• Significantly impacting your ability to perform daily activities.

Management and Prevention Strategies

Addressing knee stiffness effectively requires an accurate diagnosis of the underlying cause. Treatment may range from conservative measures like rest, ice, compression, and elevation (RICE), physical therapy, medication (NSAIDs, corticosteroids), and activity modification, to more invasive interventions like injections or surgery in severe cases.

Preventive strategies often include:

• Maintaining a healthy body weight to reduce joint stress.
• Regular, low-impact exercise to maintain joint mobility and strengthen surrounding muscles.
• Proper warm-up and cool-down routines before and after physical activity.
• Using proper biomechanics during exercise and daily movements.
• Listening to your body and avoiding activities that aggravate your knees.

Understanding the root cause of knee stiffness is the first step toward effective management and regaining optimal knee function.