C.J. McCollum – Popliteus Knee Strain

C.J. McCollum remains out with a “popliteus strain” in his left knee. The injury was suffered on March 16 and now the Blazers guard will miss his team’s upcoming four-game road trip. McCollum is currently without a timeline to return.

The popliteus is a deep muscle found just below the back of the knee (see below). It’s a thin, flat triangular muscle that assists with internal rotation of the tibia (turn your toes in and observe the direction your shinbone moves) and also “unlocks the knee”. When the knee is in full extension (fully straightened) it is locked in a stronger position – the popliteus muscle unlocks the knee when it contracts by pulling on its attachment on the posterior shaft of the tibia which allows the knee to flex (bend) and move more freely.

The footage of McCollum made it difficult initially to identify his injury as a popliteus injury. Usually, popliteus strains occur via a sudden external rotation force to the tibia which would cause micro tears in the popliteus muscle fibres as it gets stretched beyond its limit. Patients who present to the clinic with swelling and pain in the lateral or posterolateral knee plus pain with resisted internal tibial rotation can be suspected to have an isolated injury to the popliteus.

The literature on acute isolated popliteus injuries is limited. Most of the research reports popliteus injuries that occur in association with lateral or posterolateral ligamentous knee injuries which are much more severe injuries that require longer time on the sidelines. Thankfully for McCollum, this is an isolated strain of the muscle and no other structures have been reported to be implicated.

The most notable player to suffer a similar injury in the NBA was Kevin Garnett in the 2008-09 season which caused him to miss just over four weeks of action. It’s difficult to say whether McCollum may have a similar layoff – Garnett was much older and had previously dealt with knee injuries which may have contributed to his condition. We’ll have to wait for the update from the Blazers but hopefully C.J. will be back for the playoffs.

Guha et al., 2003. Popliteus tendon rupture: a case report and review of the literature. BJSM

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