Ever have knee pain in the gym with lunges?  I work with so many clients who find their strength program limited by knee pain.  It is very common for women to suffer from Patello-femoral Pain Syndrome (PFPS) as they get older.  It commonly begins affecting them around age 30.

Essentially, the cartilage behind the kneecap may soften (often referred to as chondromalacia) or break down exposing the subchondral bone (below the cartilage) to excessive stress.  There are many pain receptors in the subchondral bone region that let you know quickly when the knee is unhappy.

Activities like stair climbing, kneeling, squatting and impact exercise often bring this pain on.  Therapists and trainers have long debated whether one should lunge or squat with the foot beyond the toes.  To date, little research has been done to support the notion that allowing the knee to extend beyond the toes dramatically increases PF joint stress.

That is until now.  In a recent study in the Journal of Orthopaedic & Sports Physical Therapy (JOSPT November 2008), researchers compared a short and long step lunge both with and without a stride (stepping out and back).  The results in a nutshell confirmed that indeed a short lunge (allowing the knee to extend beyond the toes) produced more force and stress on the PF joint than a long step lunge (knee remains over the foot).  The stride with a short step and long step also produced more force than it did with a stationary lunge indicating a stationary lunge is less stressful, especially at lower knee flexion (bending) angles.

The angles where the forces really increased on descent were from 60-90 degrees.  This research would suggest that people with anterior knee pain would be better served to lunge less than 50 degrees with a  longer step length in a stationary position while rehabbing or until they build enough strength to move safely into a deeper lunge without pain.  The big takeaway here is to find the range of motion that works for you, but ultimately lengthen the step length to avoid increasing PF joint stress with lunges.

With all that said, I still believe we were designed to move in ways that the knee does extend beyond the toes.  It happens with step-over-step stair descension and sprinting/acclerating for sure.  Yet, doing 2-3 sets of weighted lunges 1-2x/week on a regular basis for strengthening in this fashion may lead to problems long term.  For those with documented PF problems, the safer route is to side with the research and listen to the body.  I hope this info serves you well in the gym moving forward!