Knee Anatomy

The knee is a complex joint made up of bones, tendons, ligaments, and muscles, all working together to ensure proper function and stability during movement. It primarily consists of the femur (thighbone) and tibia (shinbone), with the patella (kneecap) protecting the joint. Articular cartilage covers the bone surfaces to reduce friction, while the menisci act as shock absorbers. Ligaments, including the medial and lateral collateral ligaments and the anterior and posterior cruciate ligaments, provide stability. Major muscle groups, like the quadriceps and hamstrings, facilitate knee movement through their associated tendons.

Specializing Surgeon

Charles E. Stewart M.D.

Conditions & Treatments

Knee Arthritis: Causes, Types, and Symptoms

Knee arthritis is a condition where the cartilage in the knee joint breaks down, leading to pain, stiffness, and limited mobility. It can significantly impact daily activities such as walking, climbing stairs, or standing for long periods.

Causes of Knee Arthritis

The causes of knee arthritis can vary, but common factors include:

  • Osteoarthritis (OA): The most common form of knee arthritis, caused by the gradual wear and tear of cartilage over time, often associated with aging or joint overuse.
  • Rheumatoid Arthritis (RA): An autoimmune condition that causes chronic inflammation in the knee joint, leading to pain, swelling, and possible joint damage.
  • Post-Traumatic Arthritis: Develops after an injury, such as a knee fracture or ligament tear, that disrupts the integrity of the knee joint and leads to arthritis over time.
  • Infectious Arthritis: Caused by an infection in the knee joint, leading to inflammation, swelling, and pain.

Types of Knee Arthritis

  • Osteoarthritis (OA): The most common form of knee arthritis, often affecting older adults. It involves the gradual loss of cartilage, resulting in bone-on-bone contact and pain.
  • Rheumatoid Arthritis (RA): An autoimmune disorder that causes inflammation in the synovium of the knee joint, often leading to pain, swelling, and deformity.
  • Post-Traumatic Arthritis: A form of arthritis that occurs after a significant knee injury or trauma, causing damage to the cartilage and accelerating the degeneration of the joint.
  • Infectious Arthritis: Rare but serious, this type of arthritis occurs when bacteria or viruses infect the knee joint, leading to inflammation and severe pain.

Symptoms of Knee Arthritis

  • Pain: Pain in the knee, especially with movement, weight-bearing activities, or prolonged sitting.
  • Stiffness: Limited range of motion, particularly after rest or in the morning.
  • Swelling: Inflammation and puffiness around the knee joint, often causing discomfort.
  • Instability: A feeling of weakness or giving way in the knee, especially with standing or walking.
  • Crepitus: A sensation of grinding, popping, or crackling in the knee joint during movement.

Knee arthritis can significantly affect quality of life, but treatment options such as physical therapy, medications, injections, or in severe cases, knee replacement surgery, can help reduce pain and improve function.

Bursitis: Causes, Types, and Symptoms

Bursitis is the inflammation of a bursa, a small, fluid-filled sac that acts as a cushion between bones and soft tissues like muscles and tendons. When a bursa becomes irritated or inflamed, it can cause pain and swelling, making movement difficult.

Causes of Bursitis

Bursitis often results from repetitive motion, prolonged pressure, or injury to the affected area. Common causes include:

  • Repetitive Movements: Activities that involve repetitive motion, such as sports or manual labor, can lead to bursitis.
  • Trauma or Injury: A direct blow or injury to a joint can cause inflammation in the bursa.
  • Overuse: Excessive use of certain joints, especially in positions that put pressure on the bursa, can lead to irritation.
  • Infection: In rare cases, a bacterial infection can cause septic bursitis, leading to more severe symptoms.
  • Medical Conditions: Conditions like rheumatoid arthritis, gout, or diabetes can increase the risk of developing bursitis.

Common Types of Bursitis

  • Shoulder Bursitis: Inflammation of the bursa in the shoulder, often caused by repetitive overhead movements.
  • Elbow Bursitis: Also known as “student’s elbow,” it occurs when the bursa at the tip of the elbow becomes inflamed, typically from prolonged pressure or frequent leaning.
  • Hip Bursitis: Inflammation of the bursa in the hip, often caused by repetitive movements or long periods of sitting.
  • Knee Bursitis: Common in athletes or individuals who kneel frequently, this condition affects the bursa in the knee joint.

Symptoms of Bursitis

  • Pain: Aching or sharp pain in the affected joint, often aggravated by movement or pressure.
  • Swelling: Visible swelling around the affected joint.
  • Tenderness: The area around the bursa may be sensitive to touch.
  • Stiffness: Limited range of motion in the affected joint.
  • Redness and Warmth: In the case of infection, the skin may appear red and feel warm to the touch.

Bursitis can significantly affect daily activities, but treatment options such as rest, ice, anti-inflammatory medications, physical therapy, or in more severe cases, injections or surgery, can help alleviate symptoms.

Ligament Sprains: Causes, Types, and Symptoms

A ligament sprain is an injury to the tough, fibrous tissue that connects bones together and stabilizes joints. Ligament sprains can range from mild to severe, often causing pain, swelling, and difficulty moving the affected joint.

Causes of Ligament Sprains

Ligament sprains typically occur when a joint is forced beyond its normal range of motion. Common causes include:

  • Trauma: A sudden impact or forceful movement, such as a fall, car accident, or sports-related injury, can overstretch or tear ligaments.
  • Twisting or Overextending: Activities that involve rapid twisting motions, such as twisting an ankle or knee, can lead to sprains.
  • Repetitive Stress: Overuse or repetitive strain on a joint, such as during sports or strenuous physical activities, can weaken ligaments and make them more prone to injury.

Types of Ligament Sprains

Ligament sprains are classified into three grades based on the severity of the injury:

  • Grade 1 (Mild): A mild sprain occurs when the ligament is stretched but not torn. This usually causes mild pain, swelling, and minimal joint instability.
  • Grade 2 (Moderate): A moderate sprain involves partial tearing of the ligament, leading to more significant pain, swelling, bruising, and some instability in the joint.
  • Grade 3 (Severe): A severe sprain is a complete tear or rupture of the ligament, resulting in intense pain, swelling, bruising, and significant joint instability or immobility.

Common Areas Affected by Ligament Sprains

  • Ankle: One of the most common sprains, typically caused by rolling or twisting the ankle.
  • Knee: Sprains to ligaments such as the ACL (anterior cruciate ligament) or MCL (medial collateral ligament) often occur during sports or physical activities.
  • Wrist: Ligament sprains in the wrist can occur from falls or direct trauma.
  • Thumb: Sprains in the thumb are common in contact sports or activities requiring gripping.

Symptoms of Ligament Sprains

  • Pain: Localized pain in the affected joint, which may increase with movement.
  • Swelling: Inflammation around the joint, making it tender to touch.
  • Bruising: Discoloration due to blood pooling under the skin.
  • Instability: The feeling that the joint may give way or lack strength, especially in severe sprains.
  • Limited Mobility: Difficulty moving the joint due to pain or stiffness.

Treatment for ligament sprains depends on the severity of the injury and may include physical therapy, medications for pain management, and in more severe cases, surgical intervention.

Meniscus Injuries/Tears: Causes, Types, and Symptoms

The meniscus is a C-shaped cartilage in the knee that acts as a cushion and stabilizer between the femur and tibia. Meniscus tears are common knee injuries, often caused by twisting motions, impact, or degeneration over time. These injuries can lead to pain, swelling, and limited knee function.

Causes of Meniscus Injuries/Tears

Meniscus tears often occur due to:

  • Twisting or Pivoting: Sudden turns or twisting movements, especially during sports, can tear the meniscus.
  • Trauma or Impact: Direct blows or falls on the knee, such as during contact sports or accidents, can damage the meniscus.
  • Degeneration: Over time, the meniscus can weaken and become more prone to tears, especially in older adults.

Types of Meniscus Tears

Meniscus tears are classified based on their location and shape:

  • Horizontal Tear: A tear along the top and bottom of the meniscus, which may cause the meniscus to split into two parts.
  • Vertical Tear: A tear that runs vertically, often along the outer edge of the meniscus.
  • Radial Tear: A tear that radiates outward from the center of the meniscus, often causing significant instability in the knee.
  • Complex Tear: A combination of several types of tears, leading to more severe damage and symptoms.

Symptoms of Meniscus Tears

  • Pain: Pain in the knee, especially when twisting or rotating the leg.
  • Swelling: Inflammation around the knee joint, often occurring within a few hours of the injury.
  • Limited Range of Motion: Difficulty bending or straightening the knee due to pain or mechanical blockages.
  • Instability: A feeling that the knee might give way or buckle during movement.
  • Popping or Clicking Sensation: A popping sound or sensation in the knee during movement.

Treatment for meniscus tears depends on the severity and type of tear and may include physical therapy, rest, anti-inflammatory medications, or, in more severe cases, surgery.

Tendonitis and Tendinosis: Causes, Types, and Symptoms

Tendonitis and tendinosis are conditions that involve inflammation or degeneration of tendons, the thick cords that attach muscles to bones. These conditions can cause significant pain and limit movement, often affecting active individuals or those engaged in repetitive motions.

Common Types of Tendonitis and Tendinosis

Tendonitis

Tendonitis is the inflammation of a tendon, often caused by overuse, injury, or repetitive stress. It typically occurs in the shoulder, elbow, wrist, knee, or Achilles tendon. Inflammation can make the tendon swollen, painful, and less flexible. Common types include:

  • Rotator Cuff Tendonitis (shoulder)
  • Tennis Elbow (lateral epicondylitis, elbow)
  • Achilles Tendonitis (ankle)
  • Patellar Tendonitis (knee)
Tendinosis

Tendinosis is the degeneration of a tendon’s collagen due to chronic overuse, without the inflammation seen in tendonitis. This leads to weakened tendons, increasing the risk of further injury. It most often affects tendons in the:

  • Elbow (lateral epicondylitis or “tennis elbow”)
  • Knee (patellar tendon)
  • Shoulder (rotator cuff tendons)

Symptoms of Tendonitis and Tendinosis

  • Pain: Localized pain at the site of the tendon, often worsened by movement or activity.
  • Swelling: Tenderness and visible swelling around the affected tendon.
  • Stiffness: Reduced range of motion in the joint or muscle.
  • Weakness: Difficulty using the affected limb due to pain or discomfort.
  • Crepitus: A sensation of grating or crackling during movement.

Tendonitis and tendinosis can significantly impact quality of life, particularly for individuals who rely on repetitive motions. Early diagnosis and treatment, including rest, physical therapy, medications, injections, or surgery, can help manage symptoms and promote recovery.

Bone Contusions to the Knee: Causes, Types, and Symptoms

A bone contusion, or bone bruise, is an injury to the bone that causes localized swelling, pain, and bruising. Bone contusions to the knee typically occur due to trauma or impact, such as from a fall, sports injury, or direct blow to the knee. While not as severe as a fracture, bone contusions can still result in significant pain and limited mobility.

Causes of Bone Contusions to the Knee

Bone contusions in the knee are commonly caused by:

  • Direct Trauma: A direct blow to the knee, such as during contact sports (football, basketball) or from a fall, can cause a bone bruise.
  • Overuse or Repetitive Stress: Repeated stress or strain on the knee, especially in high-impact activities, may contribute to bone contusions.
  • Twisting or Rotational Movements: Sudden twisting or pivoting motions can lead to a bone bruise in the knee, especially if there is direct force involved.

Types of Bone Contusions in the Knee

  • Superficial Contusion: A mild bone bruise affecting the surface of the bone, often leading to localized swelling and discomfort.
  • Deep Contusion: A more severe bruise that penetrates deeper into the bone, often resulting in more significant pain, swelling, and longer recovery time.
  • Bone Marrow Edema: This refers to fluid buildup within the bone tissue, typically seen in more severe contusions. It can cause significant pain and may take longer to heal.

Symptoms of Bone Contusions to the Knee

  • Pain: Deep, aching pain at the site of the contusion, often aggravated by movement or pressure.
  • Swelling: Noticeable swelling around the knee joint, which may develop quickly after the injury.
  • Bruising: Discoloration of the skin due to blood accumulation under the skin, often appearing in a blue or purple color.
  • Limited Range of Motion: Difficulty moving the knee due to pain or swelling.
  • Tenderness: Increased sensitivity to touch around the injured area.

Treatment for bone contusions typically includes rest, ice, and elevation to reduce swelling and promote healing. Depending on the severity, physical therapy may also be recommended to restore knee function.

Strains: Causes, Types, and Symptoms

A strain is an injury to a muscle or tendon (the tissue that connects muscles to bones), caused by overstretching or tearing. Strains can range from mild to severe and typically result from overuse, improper movement, or sudden forceful actions. They often affect the back, hamstrings, and other muscles throughout the body, causing pain and limiting mobility.

Causes of Strains

Strains commonly occur due to:

  • Overuse or Repetitive Motion: Continuous or excessive use of a muscle without proper rest can lead to strain, especially in athletes or individuals with physically demanding jobs.
  • Sudden or Forceful Movements: Lifting heavy objects, twisting motions, or explosive actions (such as sprinting or jumping) can strain muscles or tendons.
  • Poor Flexibility or Warm-Up: Lack of proper stretching or warm-up before physical activity increases the risk of muscle strains.

Types of Strains

Strains are typically classified into three grades based on severity:

  • Grade 1 (Mild): A mild strain involves overstretching or slight tearing of the muscle or tendon fibers, causing minimal pain, swelling, and no significant loss of function.
  • Grade 2 (Moderate): A moderate strain involves partial tearing of muscle fibers, leading to moderate pain, swelling, and some loss of strength or movement.
  • Grade 3 (Severe): A severe strain refers to a complete tear of the muscle or tendon, often causing intense pain, significant swelling, bruising, and a noticeable loss of function or stability.

Symptoms of Strains

  • Pain: Sharp or aching pain in the affected muscle, which may worsen with movement or activity.
  • Swelling: Inflammation or puffiness around the injured muscle or tendon.
  • Bruising: Discoloration from blood accumulating beneath the skin.
  • Limited Range of Motion: Difficulty moving the affected area due to pain or weakness.
  • Weakness: A feeling of instability or weakness in the muscle, making it hard to perform usual movements or activities.

Treatment for strains typically includes rest, ice, compression, and elevation (R.I.C.E.), along with stretching and strengthening exercises to aid in recovery. Severe strains may require medical intervention, including physical therapy or, in some cases, surgery.

Fractures: Causes, Types, and Symptoms

A fracture refers to a break in a bone, which can result from trauma, stress, or certain medical conditions. Fractures can occur in any bone and vary in severity, often leading to pain, swelling, and difficulty moving the affected area.

Common Types of Fractures

Closed Fracture
A closed fracture occurs when the bone breaks but does not pierce the skin. These fractures can range from simple cracks to complete breaks, typically resulting from falls, accidents, or direct trauma.

Open Fracture
An open fracture, or compound fracture, happens when the bone breaks and punctures the skin. These fractures are more severe, often requiring surgical intervention to prevent infection and properly align the bone.

Stress Fracture
A stress fracture is a small, hairline crack caused by repetitive pressure or overuse, often seen in athletes or individuals engaging in high-impact activities.

Symptoms of a Fracture

  • Pain: Sudden, sharp pain at the site of the fracture.
  • Swelling: Inflammation around the injured area.
  • Bruising: Discoloration and tenderness.
  • Deformity: Visible misalignment or unnatural positioning of the bone.
  • Limited Movement: Difficulty moving the affected limb or joint.

Fractures vary in severity and treatment, with some requiring cast immobilization, while others may need surgical intervention. Prompt medical attention is crucial for proper diagnosis and recovery. If you suspect a fracture, contact an orthopedic specialist for evaluation and care.

Osteochondral Defects of the Knee: Causes, Types, and Symptoms

Osteochondral defects in the knee refer to damage to both the articular cartilage and the underlying bone. This type of injury can occur due to trauma, overuse, or degenerative conditions, leading to pain, swelling, and difficulty moving the knee joint. These defects can disrupt the smooth movement of the knee and often impact daily activities and athletic performance.

Causes of Osteochondral Defects in the Knee

Osteochondral defects are commonly caused by:

  • Trauma or Injury: Direct impact or injury to the knee, such as from a fall, car accident, or sports-related trauma, can lead to osteochondral damage.
  • Repetitive Stress: Overuse or repetitive motion of the knee, particularly in athletes or individuals with physically demanding jobs, can gradually wear down the cartilage and underlying bone.
  • Degenerative Conditions: Conditions like osteoarthritis can lead to the breakdown of both cartilage and bone, resulting in osteochondral defects.
  • Previous Knee Injuries: Previous knee injuries, such as ligament or meniscus tears, can increase the risk of developing osteochondral defects.

Types of Osteochondral Defects in the Knee

  • Grade 1: Minor damage to the cartilage without involvement of the underlying bone. Symptoms may be mild, and healing is often possible with conservative treatment.
  • Grade 2: Moderate cartilage damage with some involvement of the underlying bone. Symptoms may include pain, swelling, and decreased range of motion.
  • Grade 3: Severe damage to both cartilage and bone, often resulting in significant pain, joint instability, and difficulty walking or participating in physical activity.
  • Grade 4: The most severe form, where both cartilage and bone are significantly damaged or lost. This stage may require surgical intervention to restore knee function.

Symptoms of Osteochondral Defects in the Knee

  • Pain: A deep, aching pain in the knee, which often worsens with physical activity or after long periods of weight-bearing.
  • Swelling: Inflammation around the knee joint, which can appear shortly after an injury or after extended use.
  • Limited Range of Motion: Difficulty bending or straightening the knee due to pain or mechanical blocking.
  • Instability: A feeling that the knee may give way, especially when walking or performing weight-bearing activities.
  • Grinding or Locking: A sensation of grinding or locking in the knee, particularly when the joint moves.

Treatment for osteochondral defects typically involves conservative measures such as physical therapy, pain management, and rest. In more severe cases, surgical options like microfracture, osteochondral grafting, or cartilage replacement procedures may be considered to repair or restore the damaged cartilage and bone.

IT Band Friction Syndrome

Iliotibial (IT) band friction syndrome is a common condition that causes pain on the outside of the knee or hip, often experienced by runners, cyclists, or individuals who engage in repetitive lower body movements. This condition occurs when the IT band, a thick band of tissue running down the outside of the thigh from the hip to the knee, becomes tight or irritated, rubbing against the bones of the knee joint.

What Is IT Band Friction Syndrome?

The IT band is a strong fibrous tissue that helps stabilize the knee during movement. In IT band friction syndrome, repeated friction between the IT band and the outer part of the knee leads to inflammation and pain. The condition is often associated with overuse, improper biomechanics, or muscle imbalances that cause the IT band to become tight and irritated.

Causes of IT Band Friction Syndrome

  • Overuse: Repetitive activities such as running, cycling, or hiking, especially on uneven terrain or long distances, can stress the IT band.
  • Muscle Imbalances: Weak hip abductors or tight quadriceps can alter the way the IT band moves, increasing friction on the knee joint.
  • Poor Biomechanics: Abnormalities in walking or running form, such as overpronation or an improper stride, can contribute to the condition.
  • Inflexibility: Lack of flexibility in the hips, knees, or IT band itself can make it more prone to irritation.

Symptoms of IT Band Friction Syndrome

  • Pain on the Outer Knee: A sharp or burning pain on the outside of the knee, often worsened by activities like running, cycling, or descending stairs.
  • Pain that Worsens with Activity: The pain may start mild but can intensify with prolonged use of the affected leg or after activity.
  • Swelling or Tenderness: Swelling may occur along the outside of the knee, and the area may be tender to the touch.
  • Decreased Range of Motion: Difficulty bending or straightening the knee due to discomfort.

Treatment for IT Band Friction Syndrome

Treatment for IT band friction syndrome focuses on reducing inflammation, improving flexibility, and addressing the underlying causes of the condition. Initial treatments include rest, ice, and anti-inflammatory medications. Stretching and strengthening exercises, particularly for the hip and thigh muscles, can help relieve tension in the IT band. Physical therapy may also help improve biomechanics and prevent recurrence. In rare cases, if conservative treatments do not provide relief, corticosteroid injections or surgery may be considered.

If you’re experiencing pain or discomfort on the outside of your knee or hip, especially after physical activity, it’s important to consult with an orthopedic specialist to assess your condition and explore the most effective treatment options.