Adhesions are frond-like filaments which form in the knee in response to inflammation.
They stretch across the walls of the knee joint, binding the surfaces and limiting movement.
Initially they are easily broken with knee movement, but later the adhesion tissue matures into scar-bands and these thicken and make the knee stiff. When the knee is stiffened by adhesions the condition is called arthrofibrosis.
An 'interpretation' of a 1999 paper that gives a good overview of the subject of arthrofibrotic scarring in the knee.
An 'interpretation' of a 1994 article where the authors described their system of surgical management of arthrofibrotic scarring in the knee.