The knee is a complex joint, consisting of three compartments:
- Medial tibio-femoral compartment (the “inner part” of the knee)
- Lateral tibio-femoral compartment (the “outer part” of the knee)
- Patello-femoral compartment (the “front part” of the knee)
There are many possible causes of knee pain but usually with a good medical history and clinical examination, together with selective investigations by a doctor, it is possible to narrow down the cause of knee pain to one of the following:
Arthritis
Arthritis (from Greek “arthro”-meaning “joint” , and “itis”-referring to “inflammation”) is a form of joint disorder that involves inflammation of one or more joints. It could cause generalized knee pain, and present as a painful knee, or limping on prolonged walking. Some types of arthritis include:
- Osteoarthritis (“commonly known as wear and tear”)
- Rheumatoid arthritis
- Septic arthritis (due to infection)
- Tuberculous arthritis
- Crystal-induced arthritis (Gout or pseudogout)
- Psoriatic arthritis
- Reactive arthritis (an autoimmune reaction to an infection in another part of the body)
- Haemophilic arthritis
- Neuropathic arthropathy
- Ankylosing spondylitis
Trauma
Trauma (commonly sustained through sports injuries, accidental falls, and traffic accidents) to various structures in knee may cause pain. It could affect any of the following structures:
- Bone – Injury to bone leading to fracture of the patella or femoral condyles or tibial plateau.
- Ligaments – Either the intra-articular ligaments (Anterior cruciate & posterior cruciate ligament) or extra-articular ligaments (Medial collateral & lateral collateral ligament)
- Menisci – Structures between the femoral condyles and tibial articular surface (medial and lateral menisci)
- Strains and Sprains – Quadriceps (including 4 muscles), hamstring and patellar ligament (Patellar tendinitis – Jumper’s knee) may be injured causing knee pain.
- Patellar dislocation
Bursitis
Inflammation of the fluid filled sacs between various tendinous structures. There are around 13 bursae around knee which can be affected by chronic pressure and repetitive injuries. Some better known types of bursitis include:
- Housemaid’s knee – Prepatellar bursitis
- Clergyman’s knee – Infrapatellar bursitis
- Pes Anserinus bursitis
- Baker’s cyst – Synovial bursitis behind the knee (also known as a popliteal cyst)
Referred Pain
Some causes of knee pain are not caused by actual problems in the knee, but rather by other structures like hip joint. Pain may be referred to the knee joint in following conditions:
- Hip arthritis
- Lumbar disk herniations (Prolapsed vertebral disk)
- Slipped capital femoral epiphysis (SCFE –a condition in children where there is slipping of the femoral head from its normal position)
- Legg-Calve-Perthes disease (avascular necrosis of the femoral head in children)
Articular Cartilage Abnormalities
- Osteochondritis dissecans
- Chondromalacia
Miscellaneous Conditions
- Osgood-Schlatters’ disease (Epiphysitis of tibial tubercle)
- Sinding-Larsen-Johanssen syndrome (inflammation of patellar attachment of patellar ligament)
