Forward Lunges To Strengthen Your Knees?

Lunges by our 3 physios

A patient came in complaining of knee pain after running. Since she also did strength training with a personal trainer, she was instructed to do forward lunges (FL) to strengthen the muscles "around the knees" to avoid knee pain. Yes, the lunge is a very popular strengthening and loading exercise that is often prescribed by many health professionals. 

Alas, the front lunges made her knee pain worse.

After examining her, I explained that her knee pain was more likely coming from her hip. Meaning, she feels the pain in her knees, but the cause of her problem is her hips.

In addition, FL exert a much greater load on the patellofemoral joint compared to backward lunges (BL). I recall just reading a published article where researchers studied a group of young healthy females comparing front and back lunges.

47 body markers were placed on different parts of their bodies to record data from two force platforms in addition to 15 motion analysis cameras. The female subjects performed 10 consecutive forward and backward lunges and the researchers analyzed the middle six. 

The researchers found that peak patellofemoral joint (PFJ) reaction forces were 18.1 percent higher in FL compared to BL during the upward phase. Peak PFJ stress was 9.55 percent higher in FL compared to BL.

Peak quadriceps (or thigh) force was 18.3 percent higher in FL.  Knee bending angles were 5.85 percent larger in the upward phase of FL compared to BL. Most importantly, average PFJ loading rate was 124 percent higher in FL compared to BL. 

These results suggest strongly that there is much higher PFJ loading in the FL compared to BL. Exactly why my patient's knee pain got worse after doing her lunges. 

So if you're having knee pain, it may be best to avoid doing forward lunges until it settles. It may also be wise to strengthen your calf muscles instead.

Reference

Goulette D, Griffin P, Schiller M et al (2021). Patellofemoral Joint Loading During The Forward And Backward Lunge. Phy Ther in Sport. 47: 178-184. DOI: 10.1016/j.ptsp.2020.12.001