Jumper’s knee (also known as patellar tendinopathy) is one of the most common overuse injuries I see with athletes in the gym. Patellar tendinopathy is mainly described in our medical literature to occur with sports that require a lot of jumping (2, 4). However, weight training (squats, olympic lifts, lunges etc.) places a good deal of stress on the patellar tendon and because of this the patellar tendon can sometimes become painful and limit training. Next to patellofemoral pain syndrome (PFPS), jumper’s knee is the second most common overuse knee injury I tend to treat.
I wanted to make a comprehensive review of this common condition and how we can go about treating it, with specific focus on helping people who want to get back to training some of their favorite movements in the gym like squats, lunges, olympic lifts and jumps. So how does patellar tendinopathy commonly present?
People with patellar tendinopathy can also have pain with prolonged sitting, squatting and stairs but these symptoms can also be associated with other types of injuries like patellofemoral pain syndrome (PFPS).
PFPS is generally a more vague knee pain somewhere under or around the patella and not just localized to the patellar tendon.
Patellar tendinopathy can be a real problem because many people can’t seem to rehabilitate fully enough to get back to sport after getting hurt. Cook et al. found that more than one third of athletes presenting for treatment for patellar tendinopathy were unable to return to sport within 6 months, and it has been reported that 53% of athletes with patellar tendinopathy were forced to retire from sport (4).
Before we discuss what jumper’s knee is, we have to talk a bit about the anatomy of the area. The patellar tendon is actually a ligament that attaches the patella to the tibia of our knee. The patella also attaches to the quadriceps tendon which attaches to the quadriceps. With the aid of the quadriceps this system helps to extend (straighten) the knee and control landings from a jump and the descent of a squat.
Patellar tendinopathy usually occurs right below the patella but can also occur less commonly at the attachment of the patellar tendon and tibia (tibial tubercle) or in the quadriceps tendon itself.
Jumper’s knee is an injury to the patellar or quadriceps tendon. Jumper’s knee generally does not occur with a single traumatic event. It usually occurs gradually over time and worsens in intensity with increasing activity. It is generally thought of as an overuse injury that occurs in athletes that expose their patellar tendons to excessive stress. Insufficient recovery time between bouts of exercise may also be a player in this condition and may not allow the tendon sufficient time to remodel after training.
This results in portions of the tendon to become “pathologic” over time:
Side Note: Cook and Purdam describe this as a “doughnut” phenomenon (or donut if you live in the New England area). Basically, if you stack up a bunch of donuts one on top of another, the structure is still sound despite still having a hole right in the middle. When we have a pathological area of the tendon our rehabilitation focuses on strengthening the non-pathological tendon areas and we can still have a strong and functional tendon despite these pathologic sections (6).
Jumper’s knee was formerly known as patellar “tendinitis”. The “itis” portion of tendinitis generally refers to an inflammatory condition. We used to think that the tendon becomes painful because of inflammation in the area. What we’ve found over the course of time and with research is that this condition is generally not inflammatory in nature but more of a degenerative (wear and tear) condition (2). Basically, with excessive stress over the course of time the tendon attempts to adapt to the stress of training. The tendon goes through changes because of this stress and can sometimes become painful. This is referred to as “osis” or the “opathy” found at the end of patellar tendin-opathy.
“itis” vs “osis”
Tendons perform similarly to springs in the sense that they store and release energy. High performance activities like jumping and weight training require the patellar tendon to store and release energy just like a spring does (4). The better tendons store and release energy the better we perform these activities (4).
If we perform too much tendon intensive movement, or have insufficient rest between bouts of tendon intensive activity we don’t allow the remodeling process that normally occurs after stressing a tendon (2). This can induce pathology and changes in the tendon’s mechanical properties known as tendinopathy (2). A tendon with tendinopathy looks yellow-brown under a microscope as opposed to it’s normal white color. The collagen make-up of the tendon also becomes disorganized in comparison to it’s normal longitudinal alignment.
Tendons with tendinopathy also have something called “neovascularization” which is the growth of new vessels within the tendon (6). More neovascularization in the tendon is associated with more pain in individuals with patellar tendinopathy (6). Having these pathologic changes in your tendon increase your risk of developing pain (2).
Hold your horses, so having these tendon issues doesn’t automatically mean we’ll have pain?
No, generally only about 20% of people with radiographic evidence (MRI or Ultrasound) of tendinopathy actually have pain (7). This means that around 80% of people with tendinopathy have no pain at all (7).
In other words, tendons in your body that take stress over time are likely to develop some tendinopathy. We know this occurs in sports where certain tendons are predictably stressed (Think patellar tendinopathy in volleyball or basketball players and tennis elbow in tennis players) (7).
This doesn’t mean that you’ll develop pain but you are more likely to develop pain then someone without tendinopathy (7).
I’ll repeat this because it’s a little confusing. People with tendinopathy diagnosed with an MRI or ultrasound don’t always have pain but are at an increased risk of developing pain at some point in the future.
Not that we’ve gotten the complicated stuff out of the way here are several factors that are important in determining whether or not we go on to develop patellar tendinopathy. These are important because we can manipulate these variables to prevent future injury as well as help with rehabilitation. We’ll discuss these additional factors in the sections below.
So we already discussed that jumper’s knee is largely a condition of overuse and can occur if bouts of exercise are performed without adequate recovery to allow tendon remodeling. It’s logical that the variables below increase our risk of having patellar tendinopathy:
What other factors has our research found that correlate to people developing these tendon issues?
Side Note: Greater jump performance equating to more tendon issues is interesting. Athletes who are better at developing ground reaction forces and spend less time on the ground while jumping are more prone to develop tendon problems. Potentially the best athletes know how to best utilize the elastic nature of tendons maximally to transfer power. Because of this they simply take more stress through their tendons and are more prone to tendinopathy.
As you can see there are a few things we can control in order to prevent the onset of these issues as well as keep in mind when rehabilitating from these issues and preventing future recurrence. In the next article we’ll go through rehabilitation of these injuries.
Want more in depth information about patellar tendon injuries and how to rehabilitate them fully and get back to training? Join my Insiders Online Mentoring Program to gain access to these webinars and a 12 week training program to get you out of pain and back to squatting and weight lifting.
I Love Tendon Donuts,
Dan Pope DPT, OCS, CSCS, CF L1
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Anatomy, Causes and Treatment of Jumper’s Knee (Patellar Tendinopathy) Part 3
Anatomy, Causes and Treatment of Jumper’s Knee (Patellar Tendinopathy) Part 2