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Pain in the front of the knee is a common complaint after ACL reconstruction. The causes of the pain are varied in nature, but this post focuses on one particular and well-known type of pain: Jumper’s Knee. It is a common occurrence among athletes who participate in jumping or cutting sports, like volleyball or basketball, even without ACL reconstruction¹. For patients that do have ACL reconstruction, the likelihood of getting jumper’s knee increases based on certain conditions. This post start’s by outlining the general conditions for Jumper’s Knee and then understanding why some ACLR patients are at much higher risks for them.

Symptoms

The clinical term for Jumper’s Knee is Patellar Tendinopathy. The easiest symptoms to identify it are as follows:

Pain right below the kneecap or 1-2 cm further down.
Pain Initially appears as just soreness in the morning after playing sport, but gradually becomes worse and more consistent. If the condition is severe, it begins to affect an athlete while he or she is playing.
Gets better when warming up. Most athletes ignore the initial signs because there is no pain while playing, only the next day.
It is often exacerbated by a lot of high velocity acceleration and braking. When the condition progresses, even movements like going down the stairs become challenging.

Causes

There are numerous reasons why an athlete can get Jumper’s Knee, but it boils down to one simple concept: too much load too quickly on the patellar tendon. When reasoning about it clinically, it is often a matter of load management. Here is a simple scenario demonstrating how Jumper’s Knee may sneak up on an athlete.

Josh, a recreational volleyball player, moved to a new city and is looking to play again after a six month break. He finds a couple of open gyms and gets back to playing three times a week. After a month of participating, he begins to notice a little soreness in his right knee the day after playing, but it resolves itself within five minutes. He ignores the pain, and continues to play. However, after another month of playing, the pain has become progressively worse, beginning to affect his day to day existence.

Spikes in Volume

The smoking gun in diagnosing Jumper’s Knee is often a description of doing “nothing” followed immediately by a period of doing “a lot” with no ramp up period.

How does this impact the athlete coming back from ACL reconstruction? Athletes who get a patellar autograft already have a chunk of the patellar tendon removed, which requires time to heal. However, even athletes without a patellar tendon autograft can get Jumper’s Knee. With all ACL rehab there is an obvious period of inactivity. Combine that with a poorly planned return-to-sport rehabilitation plan and Jumper’s Knee becomes predictable, should no other injuries impede their return to sport. Far too often the later stages of rehab don’t include enough work progressive jumping work, especially for athletes operating off simple insurance based physical therapy. A progressive jumping plan is a must to let the tendon adapt to the stresses of sport.

Even non-jumping athletes are susceptible to getting Jumper’s Knee, especially after ACL reconstruction. Squatting is one way some athletes begin to experience the condition, if rehab isn’t done right. Letting the knee travel too far over the toes during a squat, and doing so repetitively with heavier weight, can overload the tendon through bouts of high compression. This form of overload is also considered a “spike in volume” with regards to a tendon that hasn’t seen action in a while. Thus, special thought must be given to the reintroduction of certain exercises, especially if the athlete has had Jumper’s Knee before.

Relative Strength

Often, athletes with Jumper’s Knee suffer from weak quadriceps too, but “weak” requires context. Athletes with exceptional force production and an extremely high jumping volume are still susceptible to the condition. But an athlete with similar quadriceps strength, less jumping volume, and a higher Body Mass Index (BMI) may experience Jumper’s Knee too². Quadriceps strength is still problematic, but there is more to the picture. Given how important quadriceps strength is to ACL reconstruction outcomes, paying very close attention to how athletes are progressing in their rehab and knowing when to reintroduce certain jumping parameters or volumes is essential to avoiding Jumper’s Knee in late stage rehab.

Biomechanics

Biomechanics play a part as well, but will always be secondary to volume. Some problems often include excessive foot pronation, reduced ankle dorsiflexion (how far the knee can travel forward with the heel on the ground), poor calf or hip abduction strength, and poor hip stability³. An athlete that presents with some of these issues may resolve their Jumper’s Knee by addressing them and reintroducing sport slowly. However, other athletes will have only a load problem, and no amount of biomechanical tweaking will fix their Jumper’s Knee.

Summary

To summarize, Jumper’s Knee has one major cause: too much, too fast. Even an athlete with poor biomechanics may not suffer from the condition if his or her body is slowly exposed to the stress of the sport over the course of one to three months. The finer points of why Jumper’s Knee occurs are:

Poor knee extensor strength (weak quadriceps).
Weak calf or hip muscles.
Poor foot mechanics or hip control.
Higher BMI.
Extremely high jumping or cutting volume.

For athletes beginning to play their sport again after ACL reconstruction, it is pivotal to ensure that either the athletes or coaches understand how much jumping or cutting they are capable of. Lack of planning can sideline an athlete again for many months.

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1. Tiemessen IJ, Kuijer PP, Hulshof CT, Frings-Dresen MH. Risk factors for developing jumper's knee in sport and occupation: a review. BMC Res Notes. 2009 Jul 8;2:127. doi: 10.1186/1756-0500-2-127. PMID: 19586529; PMCID: PMC2715413.

2. Deng M, Mansfield M. Association between Body Weight and Body Mass Index and Patellar Tendinopathy in Elite Basketball and Volleyball Players, a Systematic Review and Meta-Analysis. Healthcare (Basel). 2022 Sep 30;10(10):1928. doi: 10.3390/healthcare10101928. PMID: 36292375; PMCID: PMC9601617.