A patellar tendon tear is an extremely disabling injury that results in the inability to extend the knee.  The tear may be partial with only a few fibers tearing or a complete tear of the tendon from the inferior pole of the patella to the tibial tuberosity.  It is common in men 30 sum 40s
Clinically Relevant Anatomy
The patellar tendon is a ligament that connects bone (patella) to bone (tibial tuberosity). It is approximately 30mm wide, 50mm long and 5 to 7mm thick. The origin of the inferior pole of the patella is juxtaposed with the deep articular cartilage and Anteriorly is the patella periosteum. The tibial insertion is narrow and covers the entire tibial tubercle, which connects the quadriceps to the calf. 
A patellar tendon tear can be caused by an underlying weakening of the tendon. Inflammatory conditions; tendinitis and certain diseases; systemic lupus erythematosus rheumatoid arthritis chronic kidney disease Tendon tear. 
Other factors such as mechanical stress trauma (direct or indirect)  long-term use of corticosteroids, previous surgery around the knee obesity  may predispose individuals to patellar tendon tears.
- People with a patellar tendon tear experience the following;
- Infra patella knee pain
- Difficulty with weight-bearing
- Difficulty straightening the leg.
- In the event of a sudden contraction of the quadriceps with the knee in a flexed position, they may report hearing a “snap” or a sensation of the knee giving way 
- An indentation where a tendon is torn at the base of the kneecap. 
- When the tear is caused by a condition such as tendonitis, the tendon usually tears in the middle.
- Quadriceps tendon rupture
- Patella fracture
- Tibial tubercle avulsion fracture
The diagnosis of a patellar tendon tear should be made as early as possible to avoid adverse functional outcomes due to loss of complete knee flexion and decreased quadriceps strength.  Accurate diagnosis depends on a detailed history, physical examination, and imaging studies. . History should Include the specific location of their symptom onset pain duration pain and symptom characteristics pain relief and aggravation factors any pain radiation and symptom severity.
Physical examination should begin with examination; assess patella height and compare affected and unaffected segments. Patella tendon fractures are likely to be associated with increased patellar height relative to the uninjured side. followed by palpation of the knee and its surroundings systems showing signs of weakness and swelling. Patella tendon tears will often be associated with extensive hemarthrosis and surrounding ecchymosis.There is always a palpable defect below the lower shaft of the patella and localized tenderness about the infrapatellar aspect of the knee.
Range of motion (ROM) testing and muscle strength testing are important components of the knee evaluation Decreased ROM of the knee due to pain and damage to the extensor mechanism is an indication. It will lose dynamic knee extension which is a major physical examination finding.
Radiographic examination may identify the patella alta. MRI of the knee is an appropriate diagnostic test if a patella tendon tear is suspected. It is the most sensitive imaging modality and can make the difference between a partial and a complete rupture. Ultrasound may also be used.
The goal is early diagnosis and surgical repair of injured tendons.  Surgical management, non-surgical management and postoperative rehabilitation are required to ensure a satisfactory outcome.  and should not be delayed so far as local and general conditions permit
Surgery remains the best treatment and should not be delayed as long as local and general conditions permit . Early repair, between 2 and 6 weeks, can prevent the tendon from scarring and tightening where it was shortened. Delayed diagnosis more than 6 weeks after quadriceps rupture Contractures and fibro-adhesions complicate surgical repair and restoration of patellar tendon length. Surgical repair is necessary to restore optimal extensor function.
Physical Therapy Management
Physiotherapy management can be subdivided into: non-surgical treatment and post-operative rehabilitation
Non surgical management consists of a partial patella tendon tear with an intact knee extensor mechanism and involves immobilization in a cylindrical cast in extension for 6 weeks and progressive weight bearing exercises.  Exercises can be performed to strengthen the quadriceps muscles. In addition straight leg raising can be done. Postoperative reconstruction of a torn patella tendon
The following guidelines by vitale et al are recommended
For the first 2 weeks after surgery weight-bearing should be encouraged as tolerated and a cane and knee brace locked in full extension ROM can be inserted depending on the quality of the repair
2 to 6 weeks; weight bearing as permitted by cane and knee brace locked in full extension. Passive ROM from 0 to 90 degrees of knee flexion the active quadriceps extension
6 to 12 weeks; normalize gait on a flat surface wean crutches the knee brace can be opened to allow flexion to initiate active quadriceps contraction and gradual progression of weight bearing and knee flexion avoiding weight-bearing at knee flexed past 70 degrees .Active ROM of kneeprogressive light squat leg press core strengthening and physical therapy exercises and other techniques
12 to 16 weeks ; normalize walking on all surfaces with a brace full ROM single leg position with good control and squat to 70 degrees of flexion with good control non-impact balance and proprioceptive drill quad and core strength
16 weeks and upwards ; good quad control no pain associated with sports or occupational specific movements including impact function
- ↑ Jump up to:1.0 1.1 Gilmore JH, Clayton-Smith ZJ, Aguilar M, Pneumaticos SG, Giannoudis PV. Reconstruction techniques and clinical results of patellar tendon ruptures: Evidence today. The Knee. 2015 Jun 1;22(3):148-55.
- ↑ Jump up to:2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Hsu H, Siwiec RM. Patellar tendon rupture. InStatPearls [Internet] 2021 Jul 25. StatPearls Publishing.
- ↑ nabil ebraheim. Anatomy Of The Patellar Tendon – Everything You Need To Know – Dr. Nabil Ebraheim. Available from: http://www.youtube.com/watch?v=H9QXILgB9Mw [last accessed 23/12/2022]
- ↑ McGrory JE. Disruption of the extensor mechanism of the knee. The Journal of emergency medicine. 2003 Feb 1;24(2):163-8.
- ↑ Jump up to:5.0 5.1 Bhargava SP, Hynes MC, Dowell JK. Traumatic patella tendon rupture: early mobilisation following surgical repair. Injury. 2004 Jan 1;35(1):76-9.
- ↑ Macchi M, Spezia M, Elli S, Schiaffini G, Chisari E. Obesity increases the risk of tendinopathy, tendon tear and rupture, and postoperative complications: a systematic review of clinical studies. Clinical orthopaedics and related research. 2020 Aug;478(8):1839.
- ↑ Jump up to:7.0 7.1 7.2 Ilahiane M, Abdulrazak S, Hassani I, Marzouki A, Boutayeb F. Acute Patella Tendon Rupture A Case Report. Orthopedics and Rheumatology Open Access Journals. 2018;13(2):35-8.
- ↑ Jump up to:8.0 8.1 8.2 Fazal MA, Moonot P, Haddad F. Radiographic features of acute patellar tendon rupture. Orthopaedic Surgery. 2015 Nov;7(4):338-42.
- ↑ Murphy S, McAleese T, Elghobashy O, Walsh J. 222 Bilateral Patellar Tendon Rupture Following Low-Energy Trauma in a Young Patient Without Predisposing Risk Factors. British Journal of Surgery. 2022 Sep;109(Supplement_6):znac269-123.
- ↑ Vitale JA, Banfi G, Belli E, Negrini F, La Torre A. A 9-months multidisciplinary rehabilitation protocol based on early post-operative mobilization following. European Journal of Physical and Rehabilitation Medicine. 2018 Dec 14.