The hallmark features of patellar tendinopathy are: (1) pain localized to the inferior pole of the patella and (2) load-related pain that increases with the demand on the knee extensors, notably in activities that store and release energy in the patellar tendon (ex. jumping sports like basketball). While imaging may assist in making an accurate diagnosis, the diagnosis of patellar tendinopathy remains clinical, as asymptomatic tendon pathology may exist in people who have pain from other anterior knee sources. A thorough examination is required to diagnose patellar tendinopathy and contributing factors. Management of patellar tendinopathy should focus on progressively developing load tolerance of the tendon, the musculoskeletal unit, and the kinetic chain, as well as addressing key biomechanical and other risk factors. Rehabilitation can be slow and sometimes frustrating. Platelet-rich plasma is often used as an adjunct to a solid rehabilitation program to help expedite recovery.
Patellar tendonitis, often referred to as “Jumper’s Knee,” is a common injury seen in the orthopedic and sports medicine clinic. The hallmark features of patellar tendinitis are: (1) pain localized to the inferior pole of the patella and (2) load-related pain that increases with increasing use of the knee extensors, notably in activities that store and release energy in the patellar tendon (ex. jumping or running). While imaging may assist in making the diagnosis, patellar tendinopathy remains a clinical diagnosis, as asymptomatic tendon pathology may exist in people who have pain from other anterior knee sources (ex. Runner’s knee or PFJ syndrome). A thorough examination is required to diagnose patellar tendonitis/tendinopathy and contributing factors. The management of patellar tendinopathy should focus on progressively developing load tolerance of the tendon, the musculoskeletal unit, and the kinetic chain, as well as addressing key biomechanical and other risk factors. Rehabilitation can be slow and sometimes frustrating. Anti-inflammatory medications and injections can also help in treatment.
Blazina et al (Orthop Clin North Am, 1973) first used the term jumper’s knee (patellar tendinopathy, patellar tendinosis, patellar tendinitis) in 1973 to describe an insertional tendinopathy seen in skeletally mature athletes, although Sinding-Larson, Johansson, and Smillie once described this condition (aka. Sinding Larson Johansson Syndrome, SLJS). Jumper’s knee usually affects the attachment of the patellar tendon at the inferior patellar pole. The definition was subsequently widened to include tendinopathy of the attachment of the quadriceps tendon to the superior patellar pole or tendinopathy of the attachment of the patellar tendon to the anterior tuberosity of the tibia. The term jumper’s knee implies functional stress overload due to jumping and can affect any area of the patella tendon, including its origin at the inferior pole of the patella or its insertion at the tibial tuberosity.
The patellar tendon is a connective tissue that connects the distal pole of the patella (knee cap) to the front of the tibia (shin bone). It is an important part of the extensor mechanism of the knee and aids in extension, or straightening, of the knee. It is a continuation of the quadricep tendon, which connects the four quadriceps muscles of the thigh to the patella. The patellar tendon then runs from the inferior pole of the patella and attaches distally onto the front of the tibia at the tibial tuberosity. This attachment at the tibial tuberosity allows for extension of the knee and is important in the extensor mechanism that aids in activity such as jumping, landing, and sprinting.
Tendonitis is a chronic inflammatory process of the connective tissue that makes up a tendon. Patellar tendonitis results from constant mechanical stress exerted on the extensor mechanism that aids in jumping and extending the knee. This constant mechanical stress leads to micro-trauma of the tendon that causes cellular damage and leads to small tears within the tendon. This cellular damage is what activates the inflammation process and causes pain with activity. Broken down, tendon-itis = tendon + inflammation. If left untreated for an extended period, chronic inflammation can set in and cause chronic tendinosis. Patellar tendinosis is the chronic form of acute tendonitis and can potentially lead to more serious injuries due to the tissue architecture being weakened. This can lead to patellar tendon tearing or even patellar tendon rupture.
Minor sports injuries like patellar tendonitis often go unreported, this makes it hard to determine the frequency of patellar tendon injury. However, there has been a high prevalence of tendinosis related to the increase in jumping sports such as volleyball, basketball, as well as long and high jumping. Patellar tendinitis can be seen in adolescent athletes as well as adults into their third decade of life and is more likely to be seen in males over females.
The diagnosis of patellar tendonitis can usually be made in the clinical setting with a good history and physical exam. The patient will report an increase in activity that is associated with jumping as well as a slow increase in pain along the anterior aspect of the knee with no apparent injury or trauma. The pain will most likely be localized at the anterior aspect of the knee along the inferior pole of the patella, extending into the proximal aspect of the patellar tendon. Patients may also complain of pain that is not associated with jumping, but exacerbated but other activities such as going up or down stairs, lunging, or getting up from a seated position from a prolonged period of sitting. This pain is usually short lived and is associated with “loading” the tendon. Once the load is removed the pain diminishes.
A thorough physical exam will help diagnose patellar tendonitis. The clinician will take the patient through a series of tests that will assess the entire knee. Patients may exhibit localized pain and swelling at the anterior aspect of the knee along the patellar tendon as well as tenderness to palpation along the inferior pole of the patella and along the length of the tendon. Another physical exam finding could be the “passive extension – flexion sign”. In this test the examiner will passively extend the affected leg and palpates the patellar tendon to find the point of maximal tenderness. They will then flex the knee to 90 degrees and palpate the same location. A decrease in tenderness is a positive finding and is indicative of patellar tendinopathy. Another sign would be the “standing active quadricep sign,” when the patellar tendon is palpated with the leg fully extended and then palpated again at approximately 30 degrees of flexion. The test is positive if the pain is markedly decreased with palpation of the tendon while the knee is in a flexed position.
Plain radiographic films of the knee are typically normal in patellar tendinopathy. These films can help rule out any additional pathologies such as avulsion fractures, osteoarthritis, and calcification of the patellar tendon. Often, if calcification of the patella tendon is seen on plain radiographs, chronic patellar tendinopathy is usually the culprit. Another radiographic finding that can be seen on plain radiographs is an osteophyte along the inferior pole of the patella, called an enthesophyte. Enthesophytes can be caused by long standing traction from the chronically tight and inflamed patellar tendon. Calcification of the patellar tendon can also be seen in severe cases (see picture bottom left). MRI is usually not required to make the diagnosis of patellar tendonitis, but can help identify the source of inflammation, confirm the diagnosis (bottom right image), and rule out other pathologies. MRI is reserved for surgical planning for procedures such as patellar tendon reconstruction in cases where the patient has suffered a complete rupture of the patellar tendon from chronic tendinopathy.