Knee A to Z

Replacing damaged joint surfaces with biological structures rather than metal and plastic.

Joint replacement is removing damaged joint cartilage and underlying bone and replacing it with metal and plastic.

Joint space narrowing is when the bones of femur and tibia are closer together than normal, recognised on an X-ray taken from the front.

JRA is an abbreviation of 'juvenile rheumatoid arthritis'.

The J-sign is when the kneecap 'pops out' (subluxes) to the outer side each time the knee moves into the fully straight position (terminal extension). Page updated March 2024 by Dr Sheila Strover (Clinical Editor)

Jumper's knee is an overuse condition, also called patellar tendinitis, tendinopathy or tendinosis, where the area of attachment of the patellar tendon to the patella becomes painful.

Juvenile rheumatoid arthritis is arthritis affecting a child (under 16) in several joints where evidence exists that the condition is autoimmune - ie the child's own immune system is attacking its joints.

Juvenile traction osteochondritis is an overuse syndrome where jumping activities in a young person causes excessive pulling of the patellar tendon on the tibial tubercle.

The Kellgren-Lawrence Classification is an X-ray classification scheme for osteoarthritis of the knee.

Keyhole surgery is surgery performed with thin instruments through two or more tiny cuts, or portals.