Here we outline the common causes of knee pain. Acute knee injuries occur suddenly, usually from direct impact or twisting. Chronic knee pain develops gradually over time, often through overuse.
Select the type or location of your knee pain
Acute knee injuries
Sudden onset knee injuries involve injury to various structures of the knee, including ligaments, tendons, cartilage, and bone. Here we explain the common causes of acute knee pain:
ACL sprain – a tear or rupture of the anterior cruciate ligament. Common in contact sports and often caused by twisting or direct trauma to the knee.
MCL sprain – a tear or rupture of the medial collateral ligament on the inside of the knee.
PCL sprain – a tear or rupture of the posterior cruciate ligament in the middle of the knee.
LCL sprain – a tear or rupture of the lateral collatoral ligament on the outside of the joint. Often caused by direct trauma to the inside of the knee.
Cartilage meniscus tear – injury to the semi curcular cartilage meniscus in the knee joint. Can be an acute injury, or develop through wear and tear.
Articular/hyaline cartilage injury – damage to the hard articular cartilage which protects the ends of bones.
Patella tendon rupture – a tear or the patella tendon at the front of the knee, resulting in pain just below the patella (kneecap).
Tibial plateau fracture – a fracture of the top surface of the tibia (shin) bone.
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Lateral knee pain (outside)
Lateral knee pain refers to the outside of the knee. It usually, but not always, develops gradually through overuse. The most common causes are:
LCL sprain – injury to the lateral collateral ligament on the outside of the knee. Usually an acute knee sprain but may occur through gradually over time from overuse.
Lateral cartilage meniscus tear – wear and tear or degeneration of the cartilage meniscus on the outside of the knee joint.
Iliotibial band friction syndrome – sometimes known as runner’s knee, is an overuse injury caused by repetitive friction of the tendon over the knee.
Osteoarthritis – degeneration, wear and tear of the articular cartilage and often the actual bones themselves.
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Medial knee pain (inside)
Pain on the inside of the knee can develop gradually over time from wear and tear. Sudden onset injuries often result in injury to the medial ligament and cartilage meniscus. A major cause, particularly in older athletes, is Osteoarthritis (degeneration) of the joint. The most common causes include:
Osteoarthritis – degeneration, wear and tear in the joint can also cause pain on the inside of the knee joint.
Synovial plica irritation – inflammation resulting from a fold in the synovial membrane in the knee joint, often misdiagnosed as Patellofemoral pain.
Pes anserine bursitis – inflammation of a small sac of fluid called a bursa on the inside of the knee joint.
MCL sprain – injury to the medial collateral ligament on the inside of the knee. Usually an acute injury but can also occur from overuse, wear and tear over time.
Medial meniscus tear – degeneration of the medial cartilage meniscus on the inside of the knee.
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Posterior knee pain (back)
Some of the most common causes of gradual onset chronic pain at the back of the knee include:
Biceps femoris tendinopathy – inflammation, or more likely degeneration of the Biceps femoris tendon at the back of the knee.
Baker’s cyst – a local swelling which protrudes from the back of the knee.
Popliteus injury – is a strain of the small Popliteus muscle located at the back of the knee joint.
Hamstring tendon strain – usualy an acute injury this is a tear or one of the hamstring tendons which insert at the back of the knee (usually the Biceps femoris).
Biceps femoris avulsion – this occurs when the tendon tears pulling a small piece of bone with it.
Anterior knee (front)
This refers to the front of the knee. Injuries often involving the patella (kneecap) or the patellar tendon which connects the patella to the tibia (shin bone). The most common causes include:
Patellofemoral pain – occurs when the patella (kneecap) repeatedly rubs on the femur bone underneath.
Osgood Schlatter disease – causes pain at the front of the knee in children between the ages of 10 and 15 years old. Specifically over the bone protrusion at the top of the tibia bone.
Fat pad impingement – occurs when the infrapatellar fat pad, also sometimes known as Hoffa’s pad becomes pinched or impinged.
Patella tendonitis (Jumpers knee) – is an overuse injury causing inflammation or degeneration of the patella tendon which links the kneecap to the tibia bone.
Quadriceps tendinopathy – inflammation or degeneration of the quadriceps muscle tendon where it attaches along the top of the patella.
Knee bursitis (Housemaid’s knee) – inflammation of a small sac of fluid, called a bursa, resulting in a local swelling over the front of the patella.
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References & futher reading
- Eck C, Bekerom M, Fu F et al. Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of physical examinations with and without anaesthesia. Knee Surg Sports Traumatol Arthrosc 2013;21(8):1895–903.