Knee Pain Explained

Knee discomfort can range from a minor annoyance or slight concern to a significant issue affecting your mobility and lifestyle.

Knee pain is prevalent, affecting approximately one-third of individuals over 50 years of age in Australia. Surprisingly, only one-third of those with knee pain seek consultation with their health practitioner, with many opting for self-medication or neglecting the issue. While this might be acceptable for minor, temporary problems, persistent long-term pain poses the risk of underlying issues worsening without timely treatment.From a technical standpoint, the knee operates as a synovial hinge joint, supplied with synovial fluid for lubrication and nourishment. It functions like a hinge, moving forward and backward, but it's distinctive as it also allows for a degree of rotational movement. Despite being the body's largest hinge joint, the knee is unique in its complexity. Comprising bone, cartilage, muscle, tendon, ligament, synovial fluid, and nerves, the knee is a intricate structure. Pain in the knee may arise from issues with any one of these components or a combination thereof.

If you're grappling with knee pain and seeking insights into potential causes, the diagrams below serves as a practical guide to understanding the various reasons behind your discomfort.

DISCOMFORT AT THE KNEE JOINT

This encompasses discomfort both at the front and within the knee itself. Some possible causes:

ACL Injury: The ACL provides knee stability and controls movement; commonly damaged through twisting or sudden force, leading to pain, swelling, and instability.

Patellofemoral Pain Syndrome (Runner’s Knee): Causes dull pain around the kneecap and front of the knee, often due to overuse or misalignment.

Patella Chondromalacia: Characterised by a grating feeling and pain at the thigh-kneecap junction, caused by softening or deterioration of cartilage.

Patellofemoral Arthritis: Cartilage wear and misalignment result in bone contact, causing pain due to arthritis.

Patella Tendonitis: Over-stretching or increased stress on the patellar tendon produces a burning sensation below the kneecap.

Osgood-Schlatter Disease: Common in children or adolescents, inflammation of a growth plate below the knee results in swelling, tenderness, and tightness.

Bursitis: Inflammation of knee bursae causes swelling, tenderness, and a dull ache at the front of the knee

Osteoarthritis: Progressive joint pain and stiffness due to breakdown of articular cartilage and reduced synovial fluid lubrication.

INNER KNEE PAIN (MEDIAL SIDE)

The reasons for discomfort on the inner side of the knee are likely to be comparable in many instances to those on the outer side.

Medial Meniscus Tear or Loose Cartilage: Tears or detachment of cartilage on the inner knee side causing pain, swelling, and mobility issues.

Osteoarthritis in Medial Compartment: Wear and degeneration of cartilage in the inner knee compartment result in pain, reduced mobility, and instability.

Medial Collateral Ligament Damage: Common knee ligament injury due to stretching, partial or complete tear, often caused by outward force on the joint; symptoms include pain, stiffness, and potential bruising.

Adductor Muscles tension: A common muscle based tension that causes undue pull on the knee due to the tendon attachment.

DISCOMFORT ABOVE THE KNEE FRONT

This area corresponds to the quadriceps tendon, linking the four prominent muscles located at the front of the thigh to the knee cap. Some possible causes:

Quadriceps Tendonitis: Caused by irritation, strain, or injury to the quadriceps tendon.

Patellofemoral Arthritis: Affects the underside of the kneecap and the femur's trochlear groove. Pain arises when the articular cartilage wears away, causing bone contact.

Plica Syndrome: Inflammation of the synovial membrane fold (plica) in the knee joint, leading to pain and weakness. Often caused by repetitive knee movement, trauma, or twisting.

Lateral Patellar Facet Overload Syndrome: Dull aching pain beneath, around, or below the kneecap due to increased pressure on the lateral facet. Linked to improper tracking, poor alignment, or kneecap dislocation, especially noticeable during repetitive activities like climbing stairs.

Synovitis: Inflammation of the synovial membrane in the knee joint, resulting from overuse or trauma. Untreated synovitis may lead to swelling, pain, and is associated with conditions like arthritis and gout. Early and proper treatment is crucial to prevent complications.

OUTER KNEE PAIN (LATERAL SIDE)

This region is less prone to issues, but if discomfort arises, it might be attributed to one of the following conditions.

Hamstring Tendinitis: Inflammation of the tendon attaching the hamstring muscle (biceps femoris) to the back of the knee.

Iliotibial Band Syndrome: Inflammation of the fibrous iliotibial band on the outside of the leg, causing pain on the leg's exterior and potentially transferring to the hip.

Lateral Collateral Ligament Damage: Trauma, sprain, or tear of the ligament on the outer side of the knee, possibly involving peroneal nerve pressure and damage to the posterolateral knee corner.

Lateral Meniscus Tear: Tear, rip, or split of the crescent-shaped cartilage bands (menisci) on the outer side of the knee, leading to sudden pain, swelling, and difficulty walking.

Cyst Formation on Meniscus: Synovial fluid collection due to meniscus tear, causing pressure and a visible lump, often resulting from knee over-rotation or trauma.

Osteoarthritis in Lateral Compartment: Wear and degeneration of cartilage in the outer knee compartment, leading to pain, reduced mobility, and instability.

BACK (POSTERIOR) KNEE PAIN

Discomfort in this area frequently results from issues with muscles, tendons, or ligaments. Additional potential causes for pain at the back of the knee may be linked to synovial fluid or blood vessels.

Hamstring Tendonitis: Inflammation of the hamstring tendon connecting the hamstring muscle to the knee, resulting in sharp pain at the back of the knee due to overuse.

Hamstring Tear or Pull: Overloading the hamstring muscle can cause straining, partial tearing, or complete tearing, typically from strenuous exercise, leading to a sharp pain at the back of the thigh.

Popliteus Muscle Injury: Trauma or exercise-induced injury to the popliteus muscle, located at the back of the knee joint, may manifest as tenderness during inward leg rotation.

Posterior Cruciate Ligament Injury: Damage to the ligament within the knee, occurring when the knee is bent, ranging from partial to complete tears with potential joint instability and swelling.

Baker’s Cyst: Excessive accumulation of synovial fluid in the popliteal fossa's inflamed bursa, causing swelling behind the knee and a sensation of tightness, often linked to arthritis or trauma.

Meniscus Tear or Loose Cartilage: Stiffness and pain at the back of the knee due to a torn posterior horn of a meniscus, commonly associated with athletic activity and may manifest later.