Knee pain on the side can be debilitating, limiting mobility and impacting daily life. Understanding the potential causes, diagnosis, and treatment options is crucial for effective management. This article explores the common reasons for side knee pain, differentiating between inner and outer knee pain, and provides insights into diagnosis and treatment strategies.
Causes of Inner Knee Pain
The inner (medial) part of the knee is a complex structure of bones, ligaments, and soft tissues. Due to this intricate arrangement, pinpointing the exact cause of pain can be challenging. Common causes include:
Medial Compartment Osteoarthritis
Osteoarthritis (OA) occurs when the protective cartilage cushioning the thighbone (femur) and shinbone (tibia) deteriorates. This often affects the medial compartment of the knee, leading to friction, pain, and limited range of motion. Bone spurs (osteophytes) may also develop. Symptoms include:
- Pain during or after movement
- Morning stiffness
- Tenderness and swelling
- Reduced flexibility
- Grating or popping sensations
- Knee “catching”
OA is linked to aging, repetitive stress, prior injuries, genetics, and obesity.
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Medial Meniscus Tear
The meniscus, a C-shaped cartilage pad, acts as a shock absorber between the femur and tibia. A tear in the medial meniscus, often caused by twisting injuries or age-related wear, can result in inner knee pain, catching or locking of the joint, swelling, stiffness, limited movement, and instability.
MCL Injury
The medial collateral ligament (MCL) stabilizes the knee, preventing inward buckling. Sprains or tears, commonly occurring from sudden twists or direct blows, cause inner knee pain, tenderness, rapid swelling, popping sensations, stiffness, bruising, and instability.
Pes Anserine Bursitis
Pes anserine bursitis involves inflammation of the bursa, a fluid-filled sac cushioning the tibia and tendons of the inner knee. Repetitive activities like running or cycling can cause this condition, leading to gradual pain below the knee joint, worsened by exercise or stair climbing, along with puffiness and tenderness. Rest typically relieves pain.
Causes of Outer Knee Pain
The outer (lateral) knee is similarly susceptible to injuries. Common causes of lateral knee pain include:
Lateral Compartment Osteoarthritis
Similar to medial compartment OA, cartilage deterioration in the lateral compartment causes pain, stiffness, and limited movement on the outer knee. However, this is less common due to the outer knee’s biomechanics.
Lateral Meniscus Tear
Tears in the lateral meniscus, often from twisting injuries or degeneration, mirror medial meniscus tear symptoms but may impact knee rotation more significantly than bending or straightening. Non-weight-bearing stability is often more affected.
LCL Injury
The lateral collateral ligament (LCL) prevents outward bowing of the knee. Sprains or tears, similar to MCL injuries, result from sudden twists or direct blows. LCL injuries may also compress the nearby peroneal nerve, causing numbness or tingling in the foot.
IT Band Syndrome
Iliotibial (IT) band syndrome, common in runners, involves friction between the IT band, a long connective tissue strip, and the femur. This friction causes outer knee pain, clicking or rubbing sensations, swelling, and pain radiating up the thigh, often worsening with activity and improving with rest.
Other Causes of Side Knee Pain
Several conditions can cause pain on either side of the knee, including:
- Baker’s Cysts: Fluid-filled lumps behind the knee causing stiffness and discomfort, often associated with other knee problems.
- Osgood-Schlatter Disease: Inflammation below the kneecap in adolescents, common during growth spurts and aggravated by activities like running and jumping.
- Cancer: Bone cancer or cancer spreading to the bones can cause knee pain, often accompanied by fractures, night pain, and swelling.
- Infection: Septic arthritis, a joint infection, causes severe swelling, sudden pain, fever, and chills, typically affecting one knee.
- Injury: Knee injuries, including ligament tears, sprains, dislocations, and fractures, can cause significant pain and require medical attention.
Diagnosis
Diagnosing side knee pain involves reviewing symptoms, medical history, and conducting a physical examination. Imaging tests like X-rays, MRI, or CT scans may be necessary to confirm the diagnosis.
Treatment
Treatment varies depending on the cause and severity of the pain.
At-Home Treatment
Mild injuries often respond to rest, ice application, compression, elevation, and over-the-counter pain relievers.
Medical Options
Severe or persistent pain may require medical intervention, including physical therapy, prescription medications, injections, or surgery.
Prevention
Preventive measures include stretching before and after exercise, warming up before sports, strengthening muscles, choosing lower-impact activities, maintaining a healthy weight, and using arch support.
When to Contact a Healthcare Provider
Seek medical attention if you experience severe pain, inability to bear weight, knee instability, deformity, fever, redness, swelling, numbness, tingling, or persistent pain after home treatment.
