The NBA’s Dwayne Wade and Kyrie Irving had it. Superbowl’s most valuable player (MVP) Julian Edelman and baseball superstar Vladimir Guerrero had it, too. It has been reported that nearly every player on an NBA roster gets treated for jumper’s knee, or patellar tendonitis, on a daily basis during the season. Jumper’s knee has long plagued athletes regardless of sport or skill level. It typically affects young athletes participating in high-impact sports such as basketball, volleyball, track and field, tennis, and football. One-third to one-half of these athletes will reportedly face jumper’s knee at some point during their athletic career.
Patellar tendinopathy is one of the most well-studied overuse conditions. It was initially described in 1973 as “jumper’s knee” and can include pain at the quadriceps insertion, distal pole of the patella, or the tibial tubercle insertion.
Anatomy of the kneecap region
Functionally, the anterior anatomy of the knee is referred to as the “extensor mechanism.” The extensor mechanism is made up of the quadriceps muscles and tendon, the patella, patellar tendon, and associated retinaculum. Injuries to the extensor mechanism can occur as a result of trauma, overuse, or degenerative changes.
The most powerful soft tissue structures in the extensor mechanism are the quadriceps muscles: rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. The convergence of these muscles forms the quadriceps tendon, which inserts at the superior pole of the patella. The bulk of the patellar tendon is created by fibers from rectus femoris which covers the patella; the patellar tendon originates at the apex of the patella and inserts on the tibial tuberosity.
The naming of the patellar tendon can be confusing. Technically, the structure is a ligament as it connects bone to bone, but regardless of the anatomy, it is widely referred to as a tendon and often the terms are used interchangeably.
The patella, technically embedded in the quadriceps tendon, is the largest sesamoid or free-floating bone in the body and rests in the trochlear groove of the femur. The soft tissues surrounding the patella are ultimately responsible for maintaining its proper position. It is secured medially and laterally by retinaculum which are thickened bands of connective tissue that serve to hold structures in place.
The medial retinaculum is composed of fibers from the vastus medialis, quadriceps tendon, patellar tendon, medial collateral ligament, and the medial patellomeniscal ligament. Likewise, the lateral retinaculum is formed by the iliotibial band (tract), biceps femoris and vastus lateralis muscles, and the joint capsule.
The anterior aspect of the knee is also home to the quadriceps, prefemoral, and Hoffa’s fat pads. The suprapatellar, pretibial, and prepatellar bursae are also found here where they are critical to the healthy function of the extensor mechanism as they serve to reduce friction between the soft tissue and bony structures.
Symptoms of jumper’s knee
Individuals with jumper’s knee typically experience point-specific anterior knee pain and tenderness localized to the distal pole of the patella. The diagnosis of patellar tendinopathy is generally made in the clinic but may be supported by radiographic or magnetic resonance imaging (MRI).
There are several classification systems available for grading the severity of jumper’s knee. The first, described by Dr. Martin Blazina, who is also credited with being the first to define the condition, divides it into three clinical phases. The first phase is pain post-exercise, the second is pain at the beginning and end of activity but not during, and third is pain during and after activity. A fourth phase was added later to represent complete rupture of the tendon.
The second classification system, developed by the Victorian Institute of Sport Assessment to better quantify severity and response to treatment is made up of a series of 8 questions with a total score of 100. Higher scores indicate less severe cases of tendinopathy.
A third scale, based on duration of symptoms, is widely used. In this classification system, the term “acute” is used when symptoms have been present for less than 6 weeks, “subacute” describes symptoms present between six and 12 weeks, and “chronic” is used for symptoms lasting three months or more. The average duration of symptoms can be as long as 19 months in recreational athletes and 32 months in elite athletes. Nearly one-third of those with jumper’s knee are unable to return to sport within 6 months and more than half don’t return at all.
Although jumper’s knee may involve any portion of the patellar tendon, the proximal patellar tendon at its insertion on the inferior pole of the patella is most often affected. The symptoms most often reported by athletes with jumper’s knee are pain in the region of the patellar tendon, swelling, and limitations when running, jumping, squatting, sitting, stair-climbing, or walking.
Resting pain is not typically associated with patellar tendinopathy. The symptoms of patellar tendinopathy are often long lasting and may lead to protracted disability. A detailed history and through physical examination are key to detecting patellar tendinopathy and the clinician should be sure to inquire about sport participation, practice and competition schedules, field/court position, and level of performance.
Causes of jumper’s knee
The most common cause of jumper’s knee is overuse of the extensor mechanism of the knee. Mechanical stresses associated with athletic activities such as jumping, landing, acceleration, deceleration, and cutting may all contribute to the repetitive loading to the tendon. Constant repetition within a session, or too little recovery time between sessions, can lead to micro-tearing of the tendon. Over time, these microtears cause progressive weakening and eventual failure of the tendon.
There can be intrinsic causes of jumper’s knee as well. Ligamentous laxity, excessive Q-angle, patella alta, and pronation can predispose an individual to this pathology. Impairments of the hip, knee, and foot/ankle may directly or indirectly influence movement patterns or anatomical alignment.
Diagnosis of jumper’s knee
Making the diagnosis of patellar tendinopathy is predicated on a skilled history and physical examination. One of the most critical factors in the differential diagnosis of patellar tendinopathy is the age of the individual. Patellar tendinopathy is generally seen in adolescents. Young, active people may also incur injury related to excessive stresses to open growth plates.
Disruption of the growth plate can result in Osgood-Schlatter syndrome (a common stress reaction at the tibial tuberosity) or the less common Sinding-Larsen-Johansson syndrome (stress reaction at the inferior pole of the patella), both which may cause anterior knee pain.
The pain in this condition is typically easily identified by the patient. Pain that is variable in nature and location generally corresponds to structures in the region of the patellar tendon, whereas pain from the patellar tendon is focal (inferior pole of the patella). Radiographs may be used to exclude bony disorders such as Osgood Schlatter syndrome or osteochondritis dissecans. MRI may be used as well, however, differentiating between high-grade tendinosis and partial thickness tears is unreliable using this imaging method. Diagnostic ultrasound is likely to present a more clear picture in the differentiation of severity.
The differential diagnosis of jumper’s knee seeks to exclude patellofemoral pain, plica injury, osteochondral lesions, bursitis, and fat pad involvement. Patellar tendinopathy can easily be differentiated from quadriceps tendinopathy by the location of the pain (patellar tendon vs. quadriceps tendon). Individuals with patellofemoral pain (PFPS) often experience aggravation of their symptoms with low-load activities, such as walking, running, or cycling, whereas patellar tendinopathy usually occurs with high-load training.
Injuries to the plica are characterized by a history of a snapping sensation correlated with the clinical finding of tenderness to palpation at the site of the plica. Osteochondral lesions or defects, to the inferior region of the trochlea or patella may mimic patellar tendinopathy in terms of location of pain, but they will often be accompanied by joint effusion which indicates intra-articular injury and thus rules out tendinopathy.
Direct trauma to the anterior knee may also result in injury to any of these structures and careful attention to the location of the pain should be emphasized to rule out injury to the bursae or fat pads.
Treatments for jumper’s knee
Research has yet to determine a “best” treatment for jumper’s knee. Early recognition and diagnosis can be a helpful management strategy as the condition is often progressive. One aspect of treatment that has been well-studied is the notion that patellar tendinopathy is not inflammatory and thus the old practice of prescribing non-steroidal anti-inflammatory drugs has fallen out of favor as they are unlikely to provide long-term benefits.
Current concepts in the rehabilitation of tendinopathy suggest eccentric training may play a key role in management of these conditions. Those with jumper’s knee should avoid excessive jumping or high-impact activities which are aggravating to the knee. As pain levels improve, rehabilitation intensity should increase and eventually progress to sport-specific training. It is worth noting that tendinopathies are often difficult to manage because they are slow to respond to treatment.
This delayed treatment response has led clinicians to seek out alternative therapies such as dry needling, platelet rich plasma therapy, and extracorporeal shock wave treatment, all of which may play a role in managing the pain and symptoms associated with jumper’s knee. More research is needed to ultimately determine the efficacy of these modalities.
The last resort for the most stubborn cases of jumper’s knee is surgery. Historically, an open debridement had been the gold standard but recently an arthroscopic approach has grown in popularity. The procedure includes debridement of the anterior fat pad and patellar tendon, and longitudinal tenotomies to address persistent tight or shortened fibers of the tendon. Those who undergo arthroscopic, rather than open debridement, tend to return to normal activity more quickly.
As with any medical condition, musculoskeletal or otherwise, readers should consult with a physician or qualified medical professional to determine the best course of treatment for their condition. This article should not be considered a substitute for professional advice or care.
Jumper’s knee exercises
Eccentric exercise has long been the intervention of choice for tendinopathies. In patellar tendinopathy, single-leg squats using a decline board have been used because this position is thought to concentrate the load on the patellar tendon. Given that jumper’s knee has such a refractory response to treatment, eccentric exercise may be too aggressive for the early stages of rehabilitation making exercises intolerable.
Also, eccentric exercise has taken a backseat to heavy slow resistance training in the rehabilitation of tendinopathies. A randomized clinical trial comparing the two approaches found heavy slow resistance to be equivalent to eccentric exercise in pain levels and functional outcomes but superior in patient satisfaction.
Recently, a guideline for staging and progression of rehabilitation for jumper’s knee was proposed. The program consists of four stages: isometric loading, isotonic loading, energy-storage loading, and return to sport. Examples of the type of exercises that fit each stage are:
Phase 1: multi-angle isometrics on knee extension machine or isometric spanish squats with 70 to 90 degree knee flexion
Phase 2: isotonic knee extension, leg press, stationary lunges or split squats
Phase 3: hopping and jumping variations, acceleration from standing start, deceleration progressing from two foot stops to single-leg stops and cutting or direction changes
Phase 4: gradual return to sport specific training
During this staged progression, the emphasis should first be load modification, then progressively increasing load as dictated by pain. Some pain is acceptable during and after exercise but symptoms should quickly resolve; careful monitoring for carryover pain (pain the next morning and up to 24 hours after exercise) should be part of the program to help ensure the tissues are not being overloaded.
Conversely, underloading the tendon may not produce the desired results as the stimulus needs to reach a threshold intensity to create changes in the tendon at the cellular level. The key to success in this program is that load is progressed based on tolerance and monitored using a chosen pain provocation test during each session (e.g. decline squat).
Once all phases are complete and the patient has returned to their desired sport, they should complete a maintenance program using the phase 2 exercises at least twice a week. It is preferable to choose exercises that are loaded and single-leg, such a split squats and leg press. Isometrics can be used for their pain relieving qualities as needed throughout training.
It is critical that the individual identifies and addresses other flexibility limitations and strength deficits along the kinetic chain while recovering from, and rehabilitating jumper’s knee.
Jumper’s knee and massage therapy
Despite a lack of evidence supporting its use for tendinopathy, deep friction massage is one of the therapeutic modalities most frequently employed for jumper’s knee. It is suggested that deep friction massage can reduce adhesions, assist with realignment of collagen fibers in the tendon, and decrease pain. A 2020 study found that the immediate reduction in pain intensity was not related to the amount of pressure applied by the massage therapist, which suggests that the deep pressure typically employed during this technique may be unnecessary.
To apply this technique, the patient should be supine or long-sitting with their legs relaxed. Pressure is applied superior to the patella in the direction of the toes to create an upward tilt of the inferior pole of the patella. Cross friction strokes, moving medially and laterally across the tendon, are applied using the middle finger crossed over the index finger for strength and support. It may be useful to teach the patient to perform deep friction massage on themselves as well.
Active stretch, or pump massage, may also be used. To perform this technique the patient is seated with their legs dangling over the side of a treatment table. The therapist applies pressure at the inferior pole of the patella to pin the tendon down while simultaneously “pumping” the lower leg from extension to flexion. This technique can also be performed where the patient brings their leg from extension to flexion while the massage therapist maintains pressure over the tendon; this may also create reciprocal inhibition of the quadriceps via activation of the hamstrings.
As with any other condition, it is important that massage therapists treat the patient, not just the anatomy. The knee does not work in isolation, so addressing the soft tissues of the hip, low back, foot, and ankle regions may be indicated along with the structures directly influencing the knee.
The high prevalence of jumper’s knee in elite and recreational athletes alike, should keep this diagnosis at the top of the list when evaluating young athletes with knee pain. Though not uncommon (the list of NBA athlete’s alone is about 20 names long and full of All-Stars!), this condition is difficult to manage and requires careful attention to detail in creating an individualized approach to load management along with a lot of patience, grit, and hard work.