This passive or assisted-passive extension exercise relies on gravity to slowly improve lower limb extension.
How to do a prone hangs exercise
Lie on your belly on a firm surface like a table, supporting the thigh but allowing the lower limb to hang over the edge of the table. The limb's weight provides the stretch.
Passive stretches are gentle as long as each stretch is given a minute or so before being repeated. When an end-point is reached, the other leg can be used to gradually take the movement a few degrees further.
Peer-reviewed paperQuote from peer-reviewed paper:
"Loss of terminal extension often occurs because of hamstring contracture and quadriceps inactivation....The underlying mechanism....is not fully understood but is believed to be initiated by acute swelling, inflammation, pain, and joint laxity...[leading to] overstimulation of the hamstring muscle and inhibition of the quadriceps."
Citation: Delaloye JR, Murar J, Sánchez MG, Saithna A, Ouanezar H, Thaunat M, Vieira TD, Sonnery-Cottet B. How to Rapidly Abolish Knee Extension Deficit After Injury or Surgery: A Practice-Changing Video Pearl From the Scientific Anterior Cruciate Ligament Network International (SANTI) Study Group. Arthrosc Tech. 2018 May 7;7(6):e601-e605. doi: 10.1016/j.eats.2018.02.006. PMID: 30013901; PMCID: PMC6019855.
The importance of full extension
It is really important to regain those last few degrees of extension, because it allows 'lock-back' of the knee, so that one can stand unsupported.
Peer-reviewed paperQuote from peer-reviewed paper:
"....Regaining full symmetrical extension is a primary goal of early-phase rehabilitation after ACL reconstruction...."
Citation: Delaloye JR, Murar J, Sánchez MG, Saithna A, Ouanezar H, Thaunat M, Vieira TD, Sonnery-Cottet B. How to Rapidly Abolish Knee Extension Deficit After Injury or Surgery: A Practice-Changing Video Pearl From the Scientific Anterior Cruciate Ligament Network International (SANTI) Study Group. Arthrosc Tech. 2018 May 7;7(6):e601-e605. doi: 10.1016/j.eats.2018.02.006. PMID: 30013901; PMCID: PMC6019855.
Forum discussions
- Loss of extension
Regaining extension may be a function of both quads strengthening and extension stretching.