Understanding Lumbrical Muscle Injuries
If you climb on pockets regularly, you’ve likely encountered a strained lumbrical.
The lumbrical muscles (four of them total) get their name from their worm-like appearance, and are becoming injured more commonly.
These muscles originate from the radial sides (1&2), or in between (3&4) the FDP tendons. Their insertion is on the radial side of the proximal phalanx (extensor expansion) which means they can both flex the MCP joint, but also extend the interphalangeal joints.
The bi-pennate nature (have muscles on both sides of a tendon) of lumbricals 3 and 4 expose them to the ‘quadriga effect’. That’s a term coined by Schweizer (2003) and describes two fingers being extended (middle two) while the outside two are being flexed.
In this position, the FDP tendon of the ring finger is being pulled in both directions simultaneously. Sometimes with enough force this can end in an audible pop with pain in the palm of the hand.
See what it looks like:
Image courtesy of Complete Anatomy
lumbrical injury diagnosis
The stress test has been supported to be helpful in diagnosing lumbrical injuries. If resisting with one finger (ring only in our example) is painful and resisting with two fingers (ring + pinky) is not, then that’s a likely diagnosis.
There are multiple grades of lumbrical injuries (grade 1-3) and the severity dictates the need for follow up imaging. That’s more the exception than the rule though.
Conservative management
Conservative management is simple and supports specific loading:
moderate to high intensity
low velocity
low volume
all four fingers at a time
possible buddy taping
less variation in finger positions
Key takeaways:
Lumbrical injuries are common but can be treated with conservative management.
Let’s go from a regressive to progress mentality.