Not Another Knee Injury – Biofeedback from Start to Finish

By |2023-05-05T10:48:38-04:00May 28th, 2023|Latest Articles|

Anterior cruciate ligament (ACL) injuries tend to get a lot of attention due to their high prevalence in sports and amongst young athletes. However, the capability of biofeedback extends well beyond ACL recovery. In fact, our co-founder Russ Paine, states that the knee is the most common injuries he uses mTrigger biofeedback with. In this next case study, we are going to examine how mTrigger biofeedback can be leveraged following a different type of major knee injury – an MPFL reconstruction and OCD lesion with microfracture.

Patient History

The patient is a 15-year-old level 10 gymnast. Three years ago, she suffered 3+ right patellar dislocations while training. Soon after, she underwent a right medial patellar femoral ligament (MPFL) reconstruction and began a standard rehabilitation program. 6 months later while working back to gymnastics, she landed incorrectly and re-injured the knee. Although the MPFL reconstruction was fine, she did develop an osteochondritis dissecans (OCD) lesion on the same knee. Several months later, after failing conservative treatment, she underwent a second procedure called a microfracture to address the OCD lesion. Again, she began a standard rehabilitation program. After two major knee surgeries, months of chronic pain and swelling, her quad activation was sub-par at best. Months were spent trying to achieve adequate quad activation for basic activity, often involving electrical stimulation to help improve the process.

Just over a year later, after a complete recovery and a successful competition season, she subluxed the same right patella while training. An MRI revealed minor damage to the previously reconstructed MPFL, a MCL sprain, and a significant amount of edema. With just 12 weeks before the start of competition season, she had her work cut out for her. This is where mTrigger biofeedback came in. Previously unavailable to her, let’s look at how incorporating biofeedback early on in the recovery process help to improve her quad activation, recovery time, and ultimately help her get back to competition.

Introducing Biofeedback

Very soon after reinjury, mTrigger biofeedback along with elevation and muscle pumping (quad sets in this case) were used to begin the process of decreasing swelling and improving quad activation.

* Notice how she doesn’t get great activation yet. This makes biofeedback even more important.

For several days, re-establishing volitional quad activation was the main goal. Multiple times per day she would perform quad sets in various positions for 10 -15 min (10 sec on/10 sec off). Progressing from elevated, to sitting, to straight leg raises, to standing.

Once quad activation and swelling improved, improving gait was imperative. To focus on quad activation during initial and mid-stance of walking, we started to incorporate weight shifting onto a straight and bent leg. Focusing on quad activation and quad eccentric control.

At this point, squatting with biofeedback was an excellent way to combat faulty movement patterns and reinforce even weight distribution. It certainly wasn’t easy at first.

Over the next few weeks, exercises were progressed to a more single leg focus, but biofeedback wasn’t forgotten. Working multi angle step ups, biofeedback helped guarantee quad recruitment and control were the focus.


Eventually, to really challenge the quad and build back confidence, biofeedback was used for more demanding exercises such as single leg squats, lunges, and step downs. All eventually loaded with weight.

As you can see, single leg work was very shaky at first and biofeedback truly helped to re-establish form and control during important movement patterns.

In the final stage of rehab, mTrigger biofeedback was utilized in a unique way to access this athlete’s readiness for returning to high level activity. She passed all typical return to sport testing for the lower extremity. In this case, y-balance, isokinetic strength, and hop testing (single leg hip, triple hop, and cross over hop). However, as we have discussed before, the reliability of these RTS tests is questionable. To further explore her capacity to handle the demands of sport, we looked at a backwards, medial, and lateral hop comparison.

Check out what we found:

Backwards Hop

Medial Hop

Lateral Hop

The point of this case study is not to debate the dependability of hop testing. However, it brings up an interesting point. This athlete was unable to achieve 90%+ limb symmetry with medial, lateral, and backwards hopping. Based on these results, this athlete was given a more rigorous eccentric training and landing form program before she was allowed to fully return to hard gymnastics landings.

This athlete has since fully returned to competition and has successfully remained injury free. This case alludes to the magnitude of ways in which mTrigger sEMG biofeedback can be leveraged throughout all stages of rehab to improve outcomes, boost patient engagement, and inform clinical decision making.

More ways to use Biofeedback


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