Kyrie Irving’s knee: The troublesome past, recent surgeries, and onwards

Recent surgery to remove 2 screws and clear up an infection in Kyrie Irving’s knee has ruled him out for the rest of this season. According to the Celtics medical staff, he will likely miss 4 to 5 months.

He had originally been ruled out for only 3 to 6 weeks after a minimally invasive surgery on March 24th to remove tension wires from his patella (the kneecap). However, signs of bacterial infection were found and therefore a follow-up surgery on Kyrie Irving’s knee was performed to remove two screws from his patella.

In this piece, I’ll answer the following questions:

  • What is the anatomy and function of the patella?
  • What is the full injury history on Kyrie Irving’s knee?
  • What did the recent surgeries on Kyrie Irving’s knee entail?
  • What factors contribute to Kyrie’s return to play timeline?
  • Are there any long-term implications for Kyrie Irving’s knee?

I. The anatomy and function of the patella

A. The anatomy

The patella (aka the kneecap) is a flat, inverted triangular bone that sits on the anterior (front) part of your knee joint. It articulates with the femur (thigh bone) to form the patellofemoral joint and the underside of the patella is covered with a smooth substance called articular cartilage.

Here’s what the patella bone looks like:

kyrie irving's knee injury
Credit – McGraw HIll

Additionally, the patella is a sesamoid bone – a bone embedded within a tendon or muscle. The patella is connected to two important tendons – the quadriceps tendon from above and the patella tendon from below.

This picture shows that dual connection:

kyrie irving's knee joint
Credit – osteopathy singapore

B. The function

The patella has multiple functions.

It physically protects the knee joint, acts as a “spacer” to reduce friction, helps evenly distribute stress to the underlying bone, and the smooth undersurface (articular cartilage) helps the bones glide easily when you move the knee.

However, the primary function of the patella is to increase the lever arm (leverage) of your quadriceps muscle. The patella increases quadriceps strength by up to 50%!

The quads take on heavy load during any movement – they are responsible for extending (straightening) your knee and help eccentrically control (“brake”) the bending of your knee

During these tasks, the patella actually slides down when you flex (bend) the knee and up when you extend (straighten) the knee.

Take a look:

kyrie irving's knee
Credit – musculoskeletal glide

This change in position gives the quadriceps muscle different leverage depending on how straight or bent the knee is. Think of the patella like a balance beam – it adjusts the length, direction and force of each of its arm – the quadriceps and patella tendon – at different degrees of knee bend or straightening.

In doing so, the patella has to withstand very high forces. For example, when resisting knee flexion, the force on the patella has been shown to equal four or five times your body weight.

The strength and effectiveness of the patella is key to general movement, let alone high-level sports performance like in Kyrie’s case.

Before we get into the most recent surgeries, lets go through Kyrie Irving’s knee injury history get the full context.

II. Kyrie Irving’s knee injury history

2015 playoffs

Kyrie Irving’s knee tendonitis

Kyrie’s left knee trouble began in the 2015 playoffs. According to Kyrie, it began to bother him as he overcompensated for a sore right foot – which he aggravated nearly 3 weeks prior in game 2 of the Cavs first round sweep of the Celtics.

He was diagnosed as having patellar tendonitis. As an aside, the suffix –itis meaning inflammation is actually a misnomer. Tendon injuries are rarely characterized by inflammation, but rather disorganized tissue from excess wear and tear.

Kyrie’s explanation of overcompensation could certainly have played a part as pain in the foot can alter mechanics and thus change loading patterns throughout the lower body.

Additionally, the amount of activity he had in the 2014 summer/fall into the NBA season likely played a key role in his tendonitis. Here’s a look at his brutal schedule:

  • 2014 Summer and into early Fall
    • Kyrie was practicing with USA basketball and then playing in the FIBA World Cup (won MVP honors)
  • 2014 Fall
    • Cavaliers training camp into pre-seasoon
  • 2014-15 NBA Season
    • Kyrie played 75 out of 82 games
  • 2015 Playoffs
    • Kyrie’s first playoffs

My guess is that all this activity with little rest was the root cause of his knee tendonitis – too much activity without appropriate rest is a very common reason for tendonitis, or injury generally.

The wear and tear on Kyrie Irving’s knee patellar tendon kept building over time and then the foot injury and subsequent compensation were the straws that broke the camel’s back.

The patellar tendonitis got to the point where Kyrie said he was at “30 to 40 percent”, and it showed during their series with the Bulls. At one point, he went 5-23 with 2 assists over the course of 2 games – even though he still played 79 minutes (that’s a whole other issue – lets just say Kyrie’s knee is very happy that he wasn’t traded to Minnesota and the Thibs “40+ mins a game for starters” mentality).

2015 Finals

Kyrie Irving’s knee patellar fracture

In game 1 of the Finals, Kyrie Irving’s knee seemingly gave out as he was driving to the basket with 2 minutes left in OT. He collapsed to the ground holding that left knee. Here’s a video:

Upon further inspection, and Kyrie echoed this in his comments in the post-game, Klay’s knee made contact with Kyrie’s as he was trying to change direction. You can see that here:

kyrie irving's knee
Credit – ABC

Remember what I said above about the patella being under huge stress (4 to 5 times your bodyweight) when it’s controlling knee flexion (bending)?

Look at how much bend Kyrie’s left knee has here, placing the patella under a massive load. Klay’s contact adds an extra torque – a torque that the already stressed patella cannot handle – and it fractures. An MRI confirmed the fracture.

So what is a patella fracture?

Quite simply, it’s a break in your kneecap.

It most commonly occurs due to a direct trauma (like hitting it against the dashboard during a car accident) or indirect trauma (as in Kyrie’s cause – his quadriceps is trying to decelerate his left knee bend and the added force of Klay’s contact overloads the patella). In the latter case, the velocity of the force will determine whether the actual quadriceps tendon tears or if the patella bone fractures.

Generally, the patella can fracture in a multitude of ways. This picture is a good visual summary:

kyrie irving's knee
Credit – Physica

For our intents and purposes, we can categorize these patellar fractures into 4 types:

  1. Stable fracture
    1. This is a non-displaced fracture where the pieces of the patella may still be in contact with each other or separated by less than 3mm.
    2. Surgery usually isn’t required
  2. Displaced fracture
    1. The pieces of the patella are separated and do not line up with each other. The typically smooth joint surface may also be disrupted.
    2. Surgery is usually required
    3. Most commonly due to indirect trauma
  3. Comminuted fracture
    1. The patella fractures into three or more pieces
    2. Most commonly due to direct trauma
  4. Open fracture
    1. The patella breaks in such a way that either part of the bone sticks out through the skin or a wound penetrates all the way down to the bone.
    2. Often involves significant other damage, particularly to the soft tissues
    3. Extremely serious injury with a higher risk of infection in the wound or bone due to the break in the skin. Immediate treatment is needed to prevent possible infection.

Kyrie likely had a displaced fracture – specifically a transverse displaced fracture. Although the Cavs medical staff never gave full details, I can deduce that by his mechanism of injury (indirect trauma typically leads to transverse fractures) and type of surgery…which brings me to:

Patellar surgery for Kyrie Irving’s knee

The patellar surgery for Kyrie Irving’s knee is termed tension band wiring with cannulated screw fixation. It’s very commonly used in 2-piece non-displaced transverse fractures.

2 screws are drilled into the patella and then a wire is bound in a figure-8 shape to hold the bones together. Here’s what it looks like (work safe!):

kyrie irving's knee
Credit – AO foundation

It’s like lassoing the two patella bone pieces together to keep them connected while healing. Once the fracture has healed, the wires and screws no longer serve a purpose. Usually the hardware is left in unless it causes irritation.

Generally, the outcomes for patellar fracture surgery vary depending on the severity of the injury. However, some studies have shown that up to 80% of individuals who had surgery continued to report anterior knee pain (pain on the front of the knee).

Additionally, a longitudinal (long-term) study reported that individuals who had patellar surgery reported physical issues for an average of 6.5 years after the surgery. This study also noted that there was a trend towards better outcomes for the type of surgery Kyrie had (tension band wiring in combination with screw fixation).

The moral of the story is: you don’t want to break your patella…and if you do, hopefully you don’t need surgery.

2015-2016 Season

Kyrie returned from his patellar fracture surgery on December 20th. I couldn’t find any reported issues during that season.

He went onto play out the rest of the season and playoffs, culminating with his dagger 3 in Steph Curry’s eye during the final minute of the Cavs game 7 win over the Warriors (sorry for bringing that up again, Warriors fans).

2016-2017 Season

Kyrie Irving’s knee began to flare up towards the end of the season.

On March 16th, Kyrie took himself out of the game due to “left knee tightness”. On March 18th, he sat out the game against the Clippers. On April 7th, during a game against the Hawks, Kyrie limped to the locker room during the third quarter but returned later in the fourth.

His quotes after the game were telling, perhaps some foreshadowing:

“A terrible day for me and my knee”


“I mean it’s never easy, even the year after, just to realize that you have plates and screws in your knee and stuff like that…I don’t want it to feel sore anymore”. He added that he has “to be able to deal with it”

2017 Summer

S*** hit the fan obviously. Kyrie asked to be traded and allegedly threatened to have surgery.

It was reported Irving “needs minor knee surgery as a follow up to the procedure he underwent during the 2015 Finals to repair his broken kneecap”. Although the surgery wasn’t immediately pressing, it would “ease some of the swelling and day to day pain”.

That minor knee surgery was referring to the removal of tension wire from his patella.

2017-2018 Season

Again, Kyrie Irving’s knee flared up towards the end of the season.

On March 5th, Coach Stevens announced that Kyrie would miss their next game, vs the Bulls, due to soreness in his left knee. Additionally, Coach Stevens reported that the discomfort began during their March 3rd game against Houston but Kyrie chose to play through the pain.

Here’s what Kyrie said at the time:

“It’s been about two years coming off knee surgery, so you have to do things like that, stay on top of it and make sure you’re doing the right things….sometimes it may be a little bit extra just from the demand you put on your body and then also the realization of how much basketball you’ve actually been playing for the last few years.”

On March 11th against Indy, Kyrie played in the first half but did not return in the 2nd half. He reportedly mentioned having discomfort in the left knee at halftime, and after the game told reporters that his knee was aching more and the soreness was taking longer to subside. Generally, severity of pain and length of residual effects are two key signs of injury progression.

Kyrie then sat out the March 14th game against the Wizards. Coach Stevens again confirmed that it was due to the ongoing left knee soreness.

Kyrie traveled with the team for their 2-game road trip but didn’t play. Shams reported that Kyrie intended to seek another medical opinion later in the week. The Celtics left for a 4-game west coast roadie but Kyrie didn’t travel with the team.

On March 24th, Kyrie underwent a minimally invasive surgery (the surgeon uses the original incisions to go back into the knee rather than create new incisions) to remove the tension wires from his knee. It was reported that his patella was fully healed and knee was structurally sound. His timetable for return was set as 3-6 weeks.

Why did he need the tension wire removed?

In the majority of cases, the tension wire placed during patellar surgery doesn’t need to be replaced. It’s only removed if it is interfering with joint motion or causing irritation.

The latter was the case with Kyrie and he reportedly experienced “immediate relief” after the tension wire was removed.

However, a week later, Kyrie was ruled out for the season after needing another surgery.

What the heck happened?

During the removal of hardware, it’s considered good practice to check for infection as well. The surgeons likely removed some of the fluid from around Kyrie’s tension wire and screws and tested it in a lab for infection.

The tests came back as indicating a bacterial infection and thus Kyrie went back in for a second surgery to remove the two screws. Generally, reported hardware infection rates range from 3% to 10%.

Thankfully, the infection was not caused by MRSA. MRSA can be very difficult to deal with because it can be resistant to multiple antibiotics.

Due to the possibility of infection with metallic hardware, there’s ongoing research and investigation of non-metallic options for surgery. However, this research is still in the fledgling stages but early results have been promising.

III. Kyrie’s Irving knee rehab and return to play consideration

The Celtics medical staff has set a 4-5 month timetable for Kyrie’s return. I’ve organized his rehabilitation and return to play considerations into micro (tissue and bone), mezzo (systemic), and macro (contextual) factors.

Micro (the tissue and bone)

  • Clear out the infection.
    • Kyrie will be given a course of antibiotics to deal with the specific bacteria and the medical work-up will continue to make sure that all tissue and bone in his patella are cleared of infection. Depending on the specific type of bacteria, this can take from 2 to 6 weeks.
  • Bone healing
    • The reason why the timetable on the second procedure is so much longer is because the screw removal leaves two holes in Kyrie’s patella. This bone has to heal and re-fill. Studies show that it can take up to 18 weeks for bone mass to return to near normal after screw removal.
  • Pain, mobility, strength
    • Kyrie’s physical rehab will consist of mitigating pain, maintaining full knee joint mobility, and then a progressive step-wise strengthening progression.
    • The key with strengthening is that you want to sufficiently challenge the musculature so it remains active and doesn’t atrophy but not the point that it overloads the patella and causes pain.
    • The strengthening will begin with isometric holds (contraction without movement, progressing to contraction against resistance), move onto active movements that progressively add load, and finally progress to dynamic movement and sport-specific movements.

Mezzo (systemic factors)

  • Bio-Mechanics
    • With any injury, especially the lower body, it’s important to evaluate the bio-mechanical chain (no body part lives in isolation). Think of this chain as a railroad track – affecting it one place, whether that’s downstream or upstream, is going to have ramifications on the entire track.
    • For Kyrie’s left knee, there are two key things to evaluate – the hip abductors and ankle dorsiflexion
      1. Weak/fatigued hip abductors or poor neuro-muscular hip control can lead to the knee dropping inwards (knee valgus)
      2. Limited ankle dorsiflexion can also lead to the knee dropping inwards (knee valgus)
      3. Here’s a picture of knee valgus occurring during both jumping and landing:

        Kyrie Irving's knee
        Credit – Dove medical press
      4. In both these cases, the railroad track of the lower body is affected and it throws off the mechanics at the knee.
    • Dynamic and sport-specific movements
      • Basketball involves a lot of high intensity, high load movements in multiple directions. Jumping, in particular, puts a large stress on the patella so it’s important to review Kyrie’s jumping mechanics.
      • There’s possibility for compensatory movements due to pain or poor confidence in movement. Kyrie already mentioned this as the cause for his original left knee tendonitis (that seems like ages ago, doesn’t it?)
  • Proprioceptive and vestibular systems (feedback systems that inform the body’s awareness of itself in space)
    • These two systems are key in providing information to the brain and making small movement adjustments and adaptations.
    • The proprioceptive system can directly be affected by injury as it uses receptors near the muscles for feedback. In Kyrie’s case, residual swelling from his surgery can interfere with these receptors.
    • Due to the above, it’s important for the vestibular system (your body’s primary balance system – it involves your vision and inner-ears) to be operating at its peak and mitigate potential proprioceptive deficits.
  • Arthrogenic muscle inhibition (AMI)
    • AMI occurs due to swelling in the joint. It inhibits the contraction of the muscle. With knee joint swelling, there’s evidence of weakness in the quads because they won’t fire as effectively.
    • It’s possible Kyrie has been dealing with AMI throughout his knee injury saga.
      • He’s constantly been battling irritation and soreness (which is commonly caused by inflammation) in the left knee
      • Surgery is increases swelling in the left knee
      • He may have chronic swelling in the knee due to repetitive micro-trauma of the soft tissues surrounding his knee
    • It’s crucial to reduce knee joint swelling to restore normal quadriceps activity
  • The central nervous system (CNS) and pain science
    • Kyrie Irving’s knee pain is long-standing and chronic at this point. This can have huge ramifications on his pain perception and sensitivity to it.
    • The brain has one goal – protect its vessel (the body) and it’s constantly assessing how dangerous something is. If it perceives a threat, it sends a pain signal to alert the body to danger. Here’s an overview:

      Kyrie Irving's knee
      credit – body in mind
    • This response can be very beneficial (adaptive) in the short-term but with chronic lingering injuries, it can become detrimental (maladaptive) and continue to send pain signals even after the tissue or bone itself has healed. This is why tissue and bone healing alone aren’t indicators that a player is ready to return to play.
    • Chronic pain responses can lead to increased sensitivity of pain. There’s a saying “neurons that fire together, wire together”. Essentially, when groups of neurons fire together (like during a specific movement), they become more efficient and the threshold to activate them decreases.
    • This is great for certain things like increasing the efficiency of a movement or recognizing patterns. However, when applied to pain, constant activation of the same pain circuit (like pain with certain movements or pain in certain body regions) leads to decreased stimulus required and more efficient firing of pain circuits. This means increased sensitivity to pain & increased pain response
    • Another aspect of pain sensitivity is termed “neuro-tagging”. The brain creates memories of experiences (called neurotags or neurosignatures) to organize them efficiently. Each memory creates a certain output. For example, when you hear a certain song or smell a certain scent, it may instantly harken you back to a memory or experience. That’s due to a neurotag.
    • The same exact thing applies to pain. A certain movement or context elicits a pain response and over time, that movement is neuro-tagged as being painful – in other words, you’re conditioned to feel pain with that movement.
    • Lastly, there’s an aspect of pain science that I call “fixation”. When you have chronic pain, you tend to focus more and more on the body part and become increasingly aware of it. Studies have shown that the area in the brain responsible for that body part actually grows in size (this is called cortical re-organization). This creates increased awareness and feedback of that area (like “shining a spotlight on it”) which leads to more pain.

Macro (contextual factors)

  • Kyrie’s mental and emotional state
    • Your mental and emotional state affects your perception of injury, your mood (anger/frustration/depression/etc.), stress level, and therefore your recovery.
    • Kyrie has been through a lot with that left knee:
    • However, there are also some key positive indicators.
      • Kyrie’s IG post after the Celtics announced he would be out was characterized by resilience and forward thinking.
      • Additionally, it’s been reported that he was feeling very good after the tension wire removal and Coach Stevens said it looked like he was on pace to be back closer to 3 weeks before the infection was found. That’s huge for Kyrie’s peace of mind.
  • The Celtics current context
    • The organization itself understands the risk/reward with Kyrie and allowing his recovery to play out, extended or not. For example, here’s what Boston GM Danny Ainge said:
      • “We knew there would be maintenance issues…we’re just extra cautious. We have the good fortune of being extra cautious right now.”

    • As Ainge alluded to, the team is in a really good spot. It pains me to say it as a Laker fan but it’s the obvious truth (thank you Billy King and Colangelo). They have key veteran pieces mixed in with superstars, a bevy of young talent, and multiple draft picks.
    • There’s no reason to bring Kyrie back too soon, especially since they get Hayward back next year AND Kyrie goes into the last year of his contract. There’s a very salient cautionary tale this season, IT, of what can happen when you try to play your way back into NBA shape after a major injury.
    • On a side-note, the Celtics may now place greater priority on re-signing Rozier who has played well in Kyrie’s absence and is a nice insurance policy in the short-term.

The under-lying takeaway of all these points is this: Patience is VITAL with his rehab and return to play timeline. There are many factors at play here other than just the tissue and bone healing, and the Celtics seem to understand that risk/reward calcuation well.

IV. Are there any long-term ramifications for Kyrie Irving’s knee

Even with successful treatment, a patellar fracture does come with some long-term risk factors.

A. Arthritis

Even with the patella being healed, the articular cartilage (the smooth substance on the undersurface of the patella) can be disrupted and damaged, leading to pain and stiffness over time.

Here’s what it can look like:

kyrie irving's knee injur
Credit – Dr. Richard von Bormann

Normally, the patella is fully covered in that white substance (the articular cartilage).  Here you can see how it’s eroded and has exposed the bone.  This results in decreased gliding of the patella, changed loading patterns at the knee, and increases the risk of “bone on bone” action.

However, severe arthritis occurs in a small percent of individuals with patellar fractures. Mild to moderate arthritis is far more common.

Considering Kyrie Irving’s knee injury history, the amount of wear and tear that comes with being an NBA player, and the amount of load his quick burst, start/stop style puts on his knees – I’d say it’s more likely than not that Kyrie has to manage some pain and stiffness in that left knee  – possibly stemming from mild to moderate arthritis as he gets into the later arch of his career.

Now that doesn’t mean he will have another major injury – a lot of players effectively deal with the pain and stiffness that comes along with wear and tear to their joints.

B. Muscle weakness

As I touched upon above with AMI, there can be weakness in the quadriceps muscle following patellar surgery. For some individuals, this is a permanent and often coincides with some loss of overall motion in the knee.

For Kyrie, with the medical staff and tools he has around him, I don’t consider this to be likely at all. Swelling will be managed proactively and there will be a committed focus on getting his quad strength and activation back to normal.

C. Pain

Long-term pain has been found to be common in individuals with patellar fractures. This could be due to the chronic pain science I touched on earlier in conjunction with the arthritis and muscle weakness that can develop.

As I said before, I’d expect Kyrie Irving’s knee to have some stiffness and pain that has to be managed going forward. He may feel more comfortable wearing a knee brace or some support to give an added sense of stability and feedback.

V. The overall takeaway for Kyrie Irving’s knee

There’s no doubt that Kyrie Irving’s knee injury history, recent infection, and long-term risk factors are troublesome and obviously not ideal.

However, there are also some huge positives here. He felt instant relief after removal of the tension wire, the infection is very treatable, and he’s in a situation where the Celtics team is setup for the future and can be very patient with his recovery.

Lastly, I think the biggest takeaway for Kyrie from his ongoing knee saga is this:

Trying to “suck it up” and play through nagging irritation and pain rather than being proactive and treating it early often leads to much bigger issues down the line.

Thanks for reading and until next time.


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